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4721 lines
114 KiB
4721 lines
114 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* linux/fs/namespace.c |
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* |
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* (C) Copyright Al Viro 2000, 2001 |
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* |
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* Based on code from fs/super.c, copyright Linus Torvalds and others. |
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* Heavily rewritten. |
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*/ |
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|
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#include <linux/syscalls.h> |
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#include <linux/export.h> |
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#include <linux/capability.h> |
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#include <linux/mnt_namespace.h> |
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#include <linux/user_namespace.h> |
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#include <linux/namei.h> |
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#include <linux/security.h> |
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#include <linux/cred.h> |
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#include <linux/idr.h> |
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#include <linux/init.h> /* init_rootfs */ |
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#include <linux/fs_struct.h> /* get_fs_root et.al. */ |
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#include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ |
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#include <linux/file.h> |
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#include <linux/uaccess.h> |
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#include <linux/proc_ns.h> |
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#include <linux/magic.h> |
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#include <linux/memblock.h> |
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#include <linux/proc_fs.h> |
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#include <linux/task_work.h> |
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#include <linux/sched/task.h> |
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#include <uapi/linux/mount.h> |
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#include <linux/fs_context.h> |
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#include <linux/shmem_fs.h> |
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#include <linux/mnt_idmapping.h> |
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|
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#include "pnode.h" |
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#include "internal.h" |
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|
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/* Maximum number of mounts in a mount namespace */ |
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static unsigned int sysctl_mount_max __read_mostly = 100000; |
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|
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static unsigned int m_hash_mask __read_mostly; |
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static unsigned int m_hash_shift __read_mostly; |
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static unsigned int mp_hash_mask __read_mostly; |
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static unsigned int mp_hash_shift __read_mostly; |
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|
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static __initdata unsigned long mhash_entries; |
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static int __init set_mhash_entries(char *str) |
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{ |
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if (!str) |
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return 0; |
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mhash_entries = simple_strtoul(str, &str, 0); |
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return 1; |
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} |
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__setup("mhash_entries=", set_mhash_entries); |
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|
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static __initdata unsigned long mphash_entries; |
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static int __init set_mphash_entries(char *str) |
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{ |
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if (!str) |
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return 0; |
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mphash_entries = simple_strtoul(str, &str, 0); |
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return 1; |
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} |
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__setup("mphash_entries=", set_mphash_entries); |
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|
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static u64 event; |
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static DEFINE_IDA(mnt_id_ida); |
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static DEFINE_IDA(mnt_group_ida); |
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|
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static struct hlist_head *mount_hashtable __read_mostly; |
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static struct hlist_head *mountpoint_hashtable __read_mostly; |
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static struct kmem_cache *mnt_cache __read_mostly; |
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static DECLARE_RWSEM(namespace_sem); |
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static HLIST_HEAD(unmounted); /* protected by namespace_sem */ |
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static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */ |
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|
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struct mount_kattr { |
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unsigned int attr_set; |
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unsigned int attr_clr; |
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unsigned int propagation; |
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unsigned int lookup_flags; |
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bool recurse; |
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struct user_namespace *mnt_userns; |
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}; |
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|
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/* /sys/fs */ |
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struct kobject *fs_kobj; |
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EXPORT_SYMBOL_GPL(fs_kobj); |
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|
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/* |
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* vfsmount lock may be taken for read to prevent changes to the |
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* vfsmount hash, ie. during mountpoint lookups or walking back |
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* up the tree. |
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* |
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* It should be taken for write in all cases where the vfsmount |
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* tree or hash is modified or when a vfsmount structure is modified. |
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*/ |
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__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock); |
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|
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static inline void lock_mount_hash(void) |
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{ |
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write_seqlock(&mount_lock); |
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} |
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|
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static inline void unlock_mount_hash(void) |
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{ |
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write_sequnlock(&mount_lock); |
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} |
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static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry) |
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{ |
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unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); |
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tmp += ((unsigned long)dentry / L1_CACHE_BYTES); |
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tmp = tmp + (tmp >> m_hash_shift); |
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return &mount_hashtable[tmp & m_hash_mask]; |
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} |
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|
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static inline struct hlist_head *mp_hash(struct dentry *dentry) |
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{ |
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unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES); |
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tmp = tmp + (tmp >> mp_hash_shift); |
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return &mountpoint_hashtable[tmp & mp_hash_mask]; |
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} |
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|
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static int mnt_alloc_id(struct mount *mnt) |
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{ |
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int res = ida_alloc(&mnt_id_ida, GFP_KERNEL); |
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|
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if (res < 0) |
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return res; |
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mnt->mnt_id = res; |
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return 0; |
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} |
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static void mnt_free_id(struct mount *mnt) |
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{ |
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ida_free(&mnt_id_ida, mnt->mnt_id); |
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} |
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|
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/* |
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* Allocate a new peer group ID |
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*/ |
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static int mnt_alloc_group_id(struct mount *mnt) |
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{ |
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int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL); |
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|
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if (res < 0) |
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return res; |
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mnt->mnt_group_id = res; |
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return 0; |
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} |
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|
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/* |
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* Release a peer group ID |
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*/ |
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void mnt_release_group_id(struct mount *mnt) |
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{ |
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ida_free(&mnt_group_ida, mnt->mnt_group_id); |
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mnt->mnt_group_id = 0; |
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} |
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|
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/* |
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* vfsmount lock must be held for read |
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*/ |
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static inline void mnt_add_count(struct mount *mnt, int n) |
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{ |
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#ifdef CONFIG_SMP |
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this_cpu_add(mnt->mnt_pcp->mnt_count, n); |
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#else |
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preempt_disable(); |
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mnt->mnt_count += n; |
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preempt_enable(); |
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#endif |
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} |
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|
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/* |
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* vfsmount lock must be held for write |
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*/ |
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int mnt_get_count(struct mount *mnt) |
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{ |
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#ifdef CONFIG_SMP |
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int count = 0; |
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int cpu; |
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|
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for_each_possible_cpu(cpu) { |
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count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; |
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} |
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return count; |
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#else |
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return mnt->mnt_count; |
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#endif |
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} |
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static struct mount *alloc_vfsmnt(const char *name) |
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{ |
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struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); |
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if (mnt) { |
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int err; |
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err = mnt_alloc_id(mnt); |
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if (err) |
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goto out_free_cache; |
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if (name) { |
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mnt->mnt_devname = kstrdup_const(name, |
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GFP_KERNEL_ACCOUNT); |
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if (!mnt->mnt_devname) |
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goto out_free_id; |
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} |
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#ifdef CONFIG_SMP |
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mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); |
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if (!mnt->mnt_pcp) |
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goto out_free_devname; |
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this_cpu_add(mnt->mnt_pcp->mnt_count, 1); |
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#else |
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mnt->mnt_count = 1; |
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mnt->mnt_writers = 0; |
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#endif |
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INIT_HLIST_NODE(&mnt->mnt_hash); |
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INIT_LIST_HEAD(&mnt->mnt_child); |
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INIT_LIST_HEAD(&mnt->mnt_mounts); |
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INIT_LIST_HEAD(&mnt->mnt_list); |
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INIT_LIST_HEAD(&mnt->mnt_expire); |
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INIT_LIST_HEAD(&mnt->mnt_share); |
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INIT_LIST_HEAD(&mnt->mnt_slave_list); |
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INIT_LIST_HEAD(&mnt->mnt_slave); |
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INIT_HLIST_NODE(&mnt->mnt_mp_list); |
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INIT_LIST_HEAD(&mnt->mnt_umounting); |
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INIT_HLIST_HEAD(&mnt->mnt_stuck_children); |
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mnt->mnt.mnt_userns = &init_user_ns; |
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} |
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return mnt; |
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|
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#ifdef CONFIG_SMP |
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out_free_devname: |
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kfree_const(mnt->mnt_devname); |
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#endif |
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out_free_id: |
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mnt_free_id(mnt); |
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out_free_cache: |
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kmem_cache_free(mnt_cache, mnt); |
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return NULL; |
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} |
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|
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/* |
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* Most r/o checks on a fs are for operations that take |
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* discrete amounts of time, like a write() or unlink(). |
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* We must keep track of when those operations start |
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* (for permission checks) and when they end, so that |
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* we can determine when writes are able to occur to |
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* a filesystem. |
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*/ |
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/* |
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* __mnt_is_readonly: check whether a mount is read-only |
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* @mnt: the mount to check for its write status |
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* |
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* This shouldn't be used directly ouside of the VFS. |
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* It does not guarantee that the filesystem will stay |
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* r/w, just that it is right *now*. This can not and |
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* should not be used in place of IS_RDONLY(inode). |
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* mnt_want/drop_write() will _keep_ the filesystem |
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* r/w. |
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*/ |
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bool __mnt_is_readonly(struct vfsmount *mnt) |
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{ |
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return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb); |
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} |
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EXPORT_SYMBOL_GPL(__mnt_is_readonly); |
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static inline void mnt_inc_writers(struct mount *mnt) |
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{ |
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#ifdef CONFIG_SMP |
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this_cpu_inc(mnt->mnt_pcp->mnt_writers); |
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#else |
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mnt->mnt_writers++; |
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#endif |
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} |
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static inline void mnt_dec_writers(struct mount *mnt) |
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{ |
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#ifdef CONFIG_SMP |
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this_cpu_dec(mnt->mnt_pcp->mnt_writers); |
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#else |
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mnt->mnt_writers--; |
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#endif |
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} |
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static unsigned int mnt_get_writers(struct mount *mnt) |
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{ |
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#ifdef CONFIG_SMP |
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unsigned int count = 0; |
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int cpu; |
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for_each_possible_cpu(cpu) { |
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count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; |
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} |
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return count; |
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#else |
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return mnt->mnt_writers; |
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#endif |
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} |
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static int mnt_is_readonly(struct vfsmount *mnt) |
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{ |
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if (mnt->mnt_sb->s_readonly_remount) |
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return 1; |
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/* Order wrt setting s_flags/s_readonly_remount in do_remount() */ |
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smp_rmb(); |
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return __mnt_is_readonly(mnt); |
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} |
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|
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/* |
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* Most r/o & frozen checks on a fs are for operations that take discrete |
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* amounts of time, like a write() or unlink(). We must keep track of when |
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* those operations start (for permission checks) and when they end, so that we |
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* can determine when writes are able to occur to a filesystem. |
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*/ |
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/** |
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* __mnt_want_write - get write access to a mount without freeze protection |
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* @m: the mount on which to take a write |
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* |
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* This tells the low-level filesystem that a write is about to be performed to |
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* it, and makes sure that writes are allowed (mnt it read-write) before |
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* returning success. This operation does not protect against filesystem being |
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* frozen. When the write operation is finished, __mnt_drop_write() must be |
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* called. This is effectively a refcount. |
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*/ |
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int __mnt_want_write(struct vfsmount *m) |
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{ |
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struct mount *mnt = real_mount(m); |
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int ret = 0; |
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preempt_disable(); |
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mnt_inc_writers(mnt); |
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/* |
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* The store to mnt_inc_writers must be visible before we pass |
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* MNT_WRITE_HOLD loop below, so that the slowpath can see our |
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* incremented count after it has set MNT_WRITE_HOLD. |
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*/ |
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smp_mb(); |
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might_lock(&mount_lock.lock); |
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while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) { |
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if (!IS_ENABLED(CONFIG_PREEMPT_RT)) { |
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cpu_relax(); |
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} else { |
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/* |
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* This prevents priority inversion, if the task |
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* setting MNT_WRITE_HOLD got preempted on a remote |
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* CPU, and it prevents life lock if the task setting |
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* MNT_WRITE_HOLD has a lower priority and is bound to |
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* the same CPU as the task that is spinning here. |
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*/ |
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preempt_enable(); |
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lock_mount_hash(); |
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unlock_mount_hash(); |
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preempt_disable(); |
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} |
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} |
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/* |
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* After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will |
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* be set to match its requirements. So we must not load that until |
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* MNT_WRITE_HOLD is cleared. |
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*/ |
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smp_rmb(); |
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if (mnt_is_readonly(m)) { |
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mnt_dec_writers(mnt); |
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ret = -EROFS; |
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} |
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preempt_enable(); |
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return ret; |
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} |
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|
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/** |
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* mnt_want_write - get write access to a mount |
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* @m: the mount on which to take a write |
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* |
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* This tells the low-level filesystem that a write is about to be performed to |
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* it, and makes sure that writes are allowed (mount is read-write, filesystem |
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* is not frozen) before returning success. When the write operation is |
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* finished, mnt_drop_write() must be called. This is effectively a refcount. |
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*/ |
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int mnt_want_write(struct vfsmount *m) |
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{ |
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int ret; |
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|
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sb_start_write(m->mnt_sb); |
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ret = __mnt_want_write(m); |
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if (ret) |
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sb_end_write(m->mnt_sb); |
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return ret; |
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} |
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EXPORT_SYMBOL_GPL(mnt_want_write); |
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|
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/** |
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* __mnt_want_write_file - get write access to a file's mount |
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* @file: the file who's mount on which to take a write |
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* |
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* This is like __mnt_want_write, but if the file is already open for writing it |
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* skips incrementing mnt_writers (since the open file already has a reference) |
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* and instead only does the check for emergency r/o remounts. This must be |
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* paired with __mnt_drop_write_file. |
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*/ |
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int __mnt_want_write_file(struct file *file) |
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{ |
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if (file->f_mode & FMODE_WRITER) { |
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/* |
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* Superblock may have become readonly while there are still |
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* writable fd's, e.g. due to a fs error with errors=remount-ro |
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*/ |
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if (__mnt_is_readonly(file->f_path.mnt)) |
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return -EROFS; |
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return 0; |
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} |
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return __mnt_want_write(file->f_path.mnt); |
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} |
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|
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/** |
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* mnt_want_write_file - get write access to a file's mount |
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* @file: the file who's mount on which to take a write |
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* |
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* This is like mnt_want_write, but if the file is already open for writing it |
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* skips incrementing mnt_writers (since the open file already has a reference) |
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* and instead only does the freeze protection and the check for emergency r/o |
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* remounts. This must be paired with mnt_drop_write_file. |
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*/ |
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int mnt_want_write_file(struct file *file) |
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{ |
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int ret; |
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|
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sb_start_write(file_inode(file)->i_sb); |
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ret = __mnt_want_write_file(file); |
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if (ret) |
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sb_end_write(file_inode(file)->i_sb); |
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return ret; |
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} |
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EXPORT_SYMBOL_GPL(mnt_want_write_file); |
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|
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/** |
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* __mnt_drop_write - give up write access to a mount |
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* @mnt: the mount on which to give up write access |
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* |
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* Tells the low-level filesystem that we are done |
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* performing writes to it. Must be matched with |
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* __mnt_want_write() call above. |
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*/ |
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void __mnt_drop_write(struct vfsmount *mnt) |
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{ |
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preempt_disable(); |
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mnt_dec_writers(real_mount(mnt)); |
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preempt_enable(); |
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} |
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|
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/** |
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* mnt_drop_write - give up write access to a mount |
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* @mnt: the mount on which to give up write access |
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* |
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* Tells the low-level filesystem that we are done performing writes to it and |
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* also allows filesystem to be frozen again. Must be matched with |
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* mnt_want_write() call above. |
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*/ |
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void mnt_drop_write(struct vfsmount *mnt) |
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{ |
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__mnt_drop_write(mnt); |
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sb_end_write(mnt->mnt_sb); |
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} |
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EXPORT_SYMBOL_GPL(mnt_drop_write); |
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|
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void __mnt_drop_write_file(struct file *file) |
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{ |
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if (!(file->f_mode & FMODE_WRITER)) |
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__mnt_drop_write(file->f_path.mnt); |
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} |
|
|
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void mnt_drop_write_file(struct file *file) |
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{ |
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__mnt_drop_write_file(file); |
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sb_end_write(file_inode(file)->i_sb); |
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} |
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EXPORT_SYMBOL(mnt_drop_write_file); |
|
|
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/** |
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* mnt_hold_writers - prevent write access to the given mount |
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* @mnt: mnt to prevent write access to |
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* |
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* Prevents write access to @mnt if there are no active writers for @mnt. |
|
* This function needs to be called and return successfully before changing |
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* properties of @mnt that need to remain stable for callers with write access |
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* to @mnt. |
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* |
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* After this functions has been called successfully callers must pair it with |
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* a call to mnt_unhold_writers() in order to stop preventing write access to |
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* @mnt. |
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* |
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* Context: This function expects lock_mount_hash() to be held serializing |
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* setting MNT_WRITE_HOLD. |
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* Return: On success 0 is returned. |
|
* On error, -EBUSY is returned. |
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*/ |
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static inline int mnt_hold_writers(struct mount *mnt) |
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{ |
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mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; |
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/* |
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* After storing MNT_WRITE_HOLD, we'll read the counters. This store |
|
* should be visible before we do. |
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*/ |
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smp_mb(); |
|
|
|
/* |
|
* With writers on hold, if this value is zero, then there are |
|
* definitely no active writers (although held writers may subsequently |
|
* increment the count, they'll have to wait, and decrement it after |
|
* seeing MNT_READONLY). |
|
* |
|
* It is OK to have counter incremented on one CPU and decremented on |
|
* another: the sum will add up correctly. The danger would be when we |
|
* sum up each counter, if we read a counter before it is incremented, |
|
* but then read another CPU's count which it has been subsequently |
|
* decremented from -- we would see more decrements than we should. |
|
* MNT_WRITE_HOLD protects against this scenario, because |
|
* mnt_want_write first increments count, then smp_mb, then spins on |
|
* MNT_WRITE_HOLD, so it can't be decremented by another CPU while |
|
* we're counting up here. |
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*/ |
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if (mnt_get_writers(mnt) > 0) |
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return -EBUSY; |
|
|
|
return 0; |
|
} |
|
|
|
/** |
|
* mnt_unhold_writers - stop preventing write access to the given mount |
|
* @mnt: mnt to stop preventing write access to |
|
* |
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* Stop preventing write access to @mnt allowing callers to gain write access |
|
* to @mnt again. |
|
* |
|
* This function can only be called after a successful call to |
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* mnt_hold_writers(). |
|
* |
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* Context: This function expects lock_mount_hash() to be held. |
|
*/ |
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static inline void mnt_unhold_writers(struct mount *mnt) |
|
{ |
|
/* |
|
* MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers |
|
* that become unheld will see MNT_READONLY. |
|
*/ |
|
smp_wmb(); |
|
mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |
|
} |
|
|
|
static int mnt_make_readonly(struct mount *mnt) |
|
{ |
|
int ret; |
|
|
|
ret = mnt_hold_writers(mnt); |
|
if (!ret) |
|
mnt->mnt.mnt_flags |= MNT_READONLY; |
|
mnt_unhold_writers(mnt); |
|
return ret; |
|
} |
|
|
|
int sb_prepare_remount_readonly(struct super_block *sb) |
|
{ |
|
struct mount *mnt; |
|
int err = 0; |
|
|
|
/* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ |
|
if (atomic_long_read(&sb->s_remove_count)) |
|
return -EBUSY; |
|
|
|
lock_mount_hash(); |
|
list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { |
|
if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { |
|
err = mnt_hold_writers(mnt); |
|
if (err) |
|
break; |
|
} |
|
} |
|
if (!err && atomic_long_read(&sb->s_remove_count)) |
|
err = -EBUSY; |
|
|
|
if (!err) { |
|
sb->s_readonly_remount = 1; |
|
smp_wmb(); |
|
} |
|
list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { |
|
if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) |
|
mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |
|
} |
|
unlock_mount_hash(); |
|
|
|
return err; |
|
} |
|
|
|
static void free_vfsmnt(struct mount *mnt) |
|
{ |
|
struct user_namespace *mnt_userns; |
|
|
|
mnt_userns = mnt_user_ns(&mnt->mnt); |
|
if (!initial_idmapping(mnt_userns)) |
|
put_user_ns(mnt_userns); |
|
kfree_const(mnt->mnt_devname); |
|
#ifdef CONFIG_SMP |
|
free_percpu(mnt->mnt_pcp); |
|
#endif |
|
kmem_cache_free(mnt_cache, mnt); |
|
} |
|
|
|
static void delayed_free_vfsmnt(struct rcu_head *head) |
|
{ |
|
free_vfsmnt(container_of(head, struct mount, mnt_rcu)); |
|
} |
|
|
|
/* call under rcu_read_lock */ |
|
int __legitimize_mnt(struct vfsmount *bastard, unsigned seq) |
|
{ |
|
struct mount *mnt; |
|
if (read_seqretry(&mount_lock, seq)) |
|
return 1; |
|
if (bastard == NULL) |
|
return 0; |
|
mnt = real_mount(bastard); |
|
mnt_add_count(mnt, 1); |
|
smp_mb(); // see mntput_no_expire() |
|
if (likely(!read_seqretry(&mount_lock, seq))) |
|
return 0; |
|
if (bastard->mnt_flags & MNT_SYNC_UMOUNT) { |
|
mnt_add_count(mnt, -1); |
|
return 1; |
|
} |
|
lock_mount_hash(); |
|
if (unlikely(bastard->mnt_flags & MNT_DOOMED)) { |
|
mnt_add_count(mnt, -1); |
|
unlock_mount_hash(); |
|
return 1; |
|
} |
|
unlock_mount_hash(); |
|
/* caller will mntput() */ |
|
return -1; |
|
} |
|
|
|
/* call under rcu_read_lock */ |
|
static bool legitimize_mnt(struct vfsmount *bastard, unsigned seq) |
|
{ |
|
int res = __legitimize_mnt(bastard, seq); |
|
if (likely(!res)) |
|
return true; |
|
if (unlikely(res < 0)) { |
|
rcu_read_unlock(); |
|
mntput(bastard); |
|
rcu_read_lock(); |
|
} |
|
return false; |
|
} |
|
|
|
/* |
|
* find the first mount at @dentry on vfsmount @mnt. |
|
* call under rcu_read_lock() |
|
*/ |
|
struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) |
|
{ |
|
struct hlist_head *head = m_hash(mnt, dentry); |
|
struct mount *p; |
|
|
|
hlist_for_each_entry_rcu(p, head, mnt_hash) |
|
if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) |
|
return p; |
|
return NULL; |
|
} |
|
|
|
/* |
|
* lookup_mnt - Return the first child mount mounted at path |
|
* |
|
* "First" means first mounted chronologically. If you create the |
|
* following mounts: |
|
* |
|
* mount /dev/sda1 /mnt |
|
* mount /dev/sda2 /mnt |
|
* mount /dev/sda3 /mnt |
|
* |
|
* Then lookup_mnt() on the base /mnt dentry in the root mount will |
|
* return successively the root dentry and vfsmount of /dev/sda1, then |
|
* /dev/sda2, then /dev/sda3, then NULL. |
|
* |
|
* lookup_mnt takes a reference to the found vfsmount. |
|
*/ |
|
struct vfsmount *lookup_mnt(const struct path *path) |
|
{ |
|
struct mount *child_mnt; |
|
struct vfsmount *m; |
|
unsigned seq; |
|
|
|
rcu_read_lock(); |
|
do { |
|
seq = read_seqbegin(&mount_lock); |
|
child_mnt = __lookup_mnt(path->mnt, path->dentry); |
|
m = child_mnt ? &child_mnt->mnt : NULL; |
|
} while (!legitimize_mnt(m, seq)); |
|
rcu_read_unlock(); |
|
return m; |
|
} |
|
|
|
static inline void lock_ns_list(struct mnt_namespace *ns) |
|
{ |
|
spin_lock(&ns->ns_lock); |
|
} |
|
|
|
static inline void unlock_ns_list(struct mnt_namespace *ns) |
|
{ |
|
spin_unlock(&ns->ns_lock); |
|
} |
|
|
|
static inline bool mnt_is_cursor(struct mount *mnt) |
|
{ |
|
return mnt->mnt.mnt_flags & MNT_CURSOR; |
|
} |
|
|
|
/* |
|
* __is_local_mountpoint - Test to see if dentry is a mountpoint in the |
|
* current mount namespace. |
|
* |
|
* The common case is dentries are not mountpoints at all and that |
|
* test is handled inline. For the slow case when we are actually |
|
* dealing with a mountpoint of some kind, walk through all of the |
|
* mounts in the current mount namespace and test to see if the dentry |
|
* is a mountpoint. |
|
* |
|
* The mount_hashtable is not usable in the context because we |
|
* need to identify all mounts that may be in the current mount |
|
* namespace not just a mount that happens to have some specified |
|
* parent mount. |
|
*/ |
|
bool __is_local_mountpoint(struct dentry *dentry) |
|
{ |
|
struct mnt_namespace *ns = current->nsproxy->mnt_ns; |
|
struct mount *mnt; |
|
bool is_covered = false; |
|
|
|
down_read(&namespace_sem); |
|
lock_ns_list(ns); |
|
list_for_each_entry(mnt, &ns->list, mnt_list) { |
|
if (mnt_is_cursor(mnt)) |
|
continue; |
|
is_covered = (mnt->mnt_mountpoint == dentry); |
|
if (is_covered) |
|
break; |
|
} |
|
unlock_ns_list(ns); |
|
up_read(&namespace_sem); |
|
|
|
return is_covered; |
|
} |
|
|
|
static struct mountpoint *lookup_mountpoint(struct dentry *dentry) |
|
{ |
|
struct hlist_head *chain = mp_hash(dentry); |
|
struct mountpoint *mp; |
|
|
|
hlist_for_each_entry(mp, chain, m_hash) { |
|
if (mp->m_dentry == dentry) { |
|
mp->m_count++; |
|
return mp; |
|
} |
|
} |
|
return NULL; |
|
} |
|
|
|
static struct mountpoint *get_mountpoint(struct dentry *dentry) |
|
{ |
|
struct mountpoint *mp, *new = NULL; |
|
int ret; |
|
|
|
if (d_mountpoint(dentry)) { |
|
/* might be worth a WARN_ON() */ |
|
if (d_unlinked(dentry)) |
|
return ERR_PTR(-ENOENT); |
|
mountpoint: |
|
read_seqlock_excl(&mount_lock); |
|
mp = lookup_mountpoint(dentry); |
|
read_sequnlock_excl(&mount_lock); |
|
if (mp) |
|
goto done; |
|
} |
|
|
|
if (!new) |
|
new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL); |
|
if (!new) |
|
return ERR_PTR(-ENOMEM); |
|
|
|
|
|
/* Exactly one processes may set d_mounted */ |
|
ret = d_set_mounted(dentry); |
|
|
|
/* Someone else set d_mounted? */ |
|
if (ret == -EBUSY) |
|
goto mountpoint; |
|
|
|
/* The dentry is not available as a mountpoint? */ |
|
mp = ERR_PTR(ret); |
|
if (ret) |
|
goto done; |
|
|
|
/* Add the new mountpoint to the hash table */ |
|
read_seqlock_excl(&mount_lock); |
|
new->m_dentry = dget(dentry); |
|
new->m_count = 1; |
|
hlist_add_head(&new->m_hash, mp_hash(dentry)); |
|
INIT_HLIST_HEAD(&new->m_list); |
|
read_sequnlock_excl(&mount_lock); |
|
|
|
mp = new; |
|
new = NULL; |
|
done: |
|
kfree(new); |
|
return mp; |
|
} |
|
|
|
/* |
|
* vfsmount lock must be held. Additionally, the caller is responsible |
|
* for serializing calls for given disposal list. |
|
*/ |
|
static void __put_mountpoint(struct mountpoint *mp, struct list_head *list) |
|
{ |
|
if (!--mp->m_count) { |
|
struct dentry *dentry = mp->m_dentry; |
|
BUG_ON(!hlist_empty(&mp->m_list)); |
|
spin_lock(&dentry->d_lock); |
|
dentry->d_flags &= ~DCACHE_MOUNTED; |
|
spin_unlock(&dentry->d_lock); |
|
dput_to_list(dentry, list); |
|
hlist_del(&mp->m_hash); |
|
kfree(mp); |
|
} |
|
} |
|
|
|
/* called with namespace_lock and vfsmount lock */ |
|
static void put_mountpoint(struct mountpoint *mp) |
|
{ |
|
__put_mountpoint(mp, &ex_mountpoints); |
|
} |
|
|
|
static inline int check_mnt(struct mount *mnt) |
|
{ |
|
return mnt->mnt_ns == current->nsproxy->mnt_ns; |
|
} |
|
|
|
/* |
|
* vfsmount lock must be held for write |
|
*/ |
|
static void touch_mnt_namespace(struct mnt_namespace *ns) |
|
{ |
|
if (ns) { |
|
ns->event = ++event; |
|
wake_up_interruptible(&ns->poll); |
|
} |
|
} |
|
|
|
/* |
|
* vfsmount lock must be held for write |
|
*/ |
|
static void __touch_mnt_namespace(struct mnt_namespace *ns) |
|
{ |
|
if (ns && ns->event != event) { |
|
ns->event = event; |
|
wake_up_interruptible(&ns->poll); |
|
} |
|
} |
|
|
|
/* |
|
* vfsmount lock must be held for write |
|
*/ |
|
static struct mountpoint *unhash_mnt(struct mount *mnt) |
|
{ |
|
struct mountpoint *mp; |
|
mnt->mnt_parent = mnt; |
|
mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
|
list_del_init(&mnt->mnt_child); |
|
hlist_del_init_rcu(&mnt->mnt_hash); |
|
hlist_del_init(&mnt->mnt_mp_list); |
|
mp = mnt->mnt_mp; |
|
mnt->mnt_mp = NULL; |
|
return mp; |
|
} |
|
|
|
/* |
|
* vfsmount lock must be held for write |
|
*/ |
|
static void umount_mnt(struct mount *mnt) |
|
{ |
|
put_mountpoint(unhash_mnt(mnt)); |
|
} |
|
|
|
/* |
|
* vfsmount lock must be held for write |
|
*/ |
|
void mnt_set_mountpoint(struct mount *mnt, |
|
struct mountpoint *mp, |
|
struct mount *child_mnt) |
|
{ |
|
mp->m_count++; |
|
mnt_add_count(mnt, 1); /* essentially, that's mntget */ |
|
child_mnt->mnt_mountpoint = mp->m_dentry; |
|
child_mnt->mnt_parent = mnt; |
|
child_mnt->mnt_mp = mp; |
|
hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list); |
|
} |
|
|
|
static void __attach_mnt(struct mount *mnt, struct mount *parent) |
|
{ |
|
hlist_add_head_rcu(&mnt->mnt_hash, |
|
m_hash(&parent->mnt, mnt->mnt_mountpoint)); |
|
list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
|
} |
|
|
|
/* |
|
* vfsmount lock must be held for write |
|
*/ |
|
static void attach_mnt(struct mount *mnt, |
|
struct mount *parent, |
|
struct mountpoint *mp) |
|
{ |
|
mnt_set_mountpoint(parent, mp, mnt); |
|
__attach_mnt(mnt, parent); |
|
} |
|
|
|
void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt) |
|
{ |
|
struct mountpoint *old_mp = mnt->mnt_mp; |
|
struct mount *old_parent = mnt->mnt_parent; |
|
|
|
list_del_init(&mnt->mnt_child); |
|
hlist_del_init(&mnt->mnt_mp_list); |
|
hlist_del_init_rcu(&mnt->mnt_hash); |
|
|
|
attach_mnt(mnt, parent, mp); |
|
|
|
put_mountpoint(old_mp); |
|
mnt_add_count(old_parent, -1); |
|
} |
|
|
|
/* |
|
* vfsmount lock must be held for write |
|
*/ |
|
static void commit_tree(struct mount *mnt) |
|
{ |
|
struct mount *parent = mnt->mnt_parent; |
|
struct mount *m; |
|
LIST_HEAD(head); |
|
struct mnt_namespace *n = parent->mnt_ns; |
|
|
|
BUG_ON(parent == mnt); |
|
|
|
list_add_tail(&head, &mnt->mnt_list); |
|
list_for_each_entry(m, &head, mnt_list) |
|
m->mnt_ns = n; |
|
|
|
list_splice(&head, n->list.prev); |
|
|
|
n->mounts += n->pending_mounts; |
|
n->pending_mounts = 0; |
|
|
|
__attach_mnt(mnt, parent); |
|
touch_mnt_namespace(n); |
|
} |
|
|
|
static struct mount *next_mnt(struct mount *p, struct mount *root) |
|
{ |
|
struct list_head *next = p->mnt_mounts.next; |
|
if (next == &p->mnt_mounts) { |
|
while (1) { |
|
if (p == root) |
|
return NULL; |
|
next = p->mnt_child.next; |
|
if (next != &p->mnt_parent->mnt_mounts) |
|
break; |
|
p = p->mnt_parent; |
|
} |
|
} |
|
return list_entry(next, struct mount, mnt_child); |
|
} |
|
|
|
static struct mount *skip_mnt_tree(struct mount *p) |
|
{ |
|
struct list_head *prev = p->mnt_mounts.prev; |
|
while (prev != &p->mnt_mounts) { |
|
p = list_entry(prev, struct mount, mnt_child); |
|
prev = p->mnt_mounts.prev; |
|
} |
|
return p; |
|
} |
|
|
|
/** |
|
* vfs_create_mount - Create a mount for a configured superblock |
|
* @fc: The configuration context with the superblock attached |
|
* |
|
* Create a mount to an already configured superblock. If necessary, the |
|
* caller should invoke vfs_get_tree() before calling this. |
|
* |
|
* Note that this does not attach the mount to anything. |
|
*/ |
|
struct vfsmount *vfs_create_mount(struct fs_context *fc) |
|
{ |
|
struct mount *mnt; |
|
struct user_namespace *fs_userns; |
|
|
|
if (!fc->root) |
|
return ERR_PTR(-EINVAL); |
|
|
|
mnt = alloc_vfsmnt(fc->source ?: "none"); |
|
if (!mnt) |
|
return ERR_PTR(-ENOMEM); |
|
|
|
if (fc->sb_flags & SB_KERNMOUNT) |
|
mnt->mnt.mnt_flags = MNT_INTERNAL; |
|
|
|
atomic_inc(&fc->root->d_sb->s_active); |
|
mnt->mnt.mnt_sb = fc->root->d_sb; |
|
mnt->mnt.mnt_root = dget(fc->root); |
|
mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
|
mnt->mnt_parent = mnt; |
|
|
|
fs_userns = mnt->mnt.mnt_sb->s_user_ns; |
|
if (!initial_idmapping(fs_userns)) |
|
mnt->mnt.mnt_userns = get_user_ns(fs_userns); |
|
|
|
lock_mount_hash(); |
|
list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts); |
|
unlock_mount_hash(); |
|
return &mnt->mnt; |
|
} |
|
EXPORT_SYMBOL(vfs_create_mount); |
|
|
|
struct vfsmount *fc_mount(struct fs_context *fc) |
|
{ |
|
int err = vfs_get_tree(fc); |
|
if (!err) { |
|
up_write(&fc->root->d_sb->s_umount); |
|
return vfs_create_mount(fc); |
|
} |
|
return ERR_PTR(err); |
|
} |
|
EXPORT_SYMBOL(fc_mount); |
|
|
|
struct vfsmount *vfs_kern_mount(struct file_system_type *type, |
|
int flags, const char *name, |
|
void *data) |
|
{ |
|
struct fs_context *fc; |
|
struct vfsmount *mnt; |
|
int ret = 0; |
|
|
|
if (!type) |
|
return ERR_PTR(-EINVAL); |
|
|
|
fc = fs_context_for_mount(type, flags); |
|
if (IS_ERR(fc)) |
|
return ERR_CAST(fc); |
|
|
|
if (name) |
|
ret = vfs_parse_fs_string(fc, "source", |
|
name, strlen(name)); |
|
if (!ret) |
|
ret = parse_monolithic_mount_data(fc, data); |
|
if (!ret) |
|
mnt = fc_mount(fc); |
|
else |
|
mnt = ERR_PTR(ret); |
|
|
|
put_fs_context(fc); |
|
return mnt; |
|
} |
|
EXPORT_SYMBOL_GPL(vfs_kern_mount); |
|
|
|
struct vfsmount * |
|
vfs_submount(const struct dentry *mountpoint, struct file_system_type *type, |
|
const char *name, void *data) |
|
{ |
|
/* Until it is worked out how to pass the user namespace |
|
* through from the parent mount to the submount don't support |
|
* unprivileged mounts with submounts. |
|
*/ |
|
if (mountpoint->d_sb->s_user_ns != &init_user_ns) |
|
return ERR_PTR(-EPERM); |
|
|
|
return vfs_kern_mount(type, SB_SUBMOUNT, name, data); |
|
} |
|
EXPORT_SYMBOL_GPL(vfs_submount); |
|
|
|
static struct mount *clone_mnt(struct mount *old, struct dentry *root, |
|
int flag) |
|
{ |
|
struct super_block *sb = old->mnt.mnt_sb; |
|
struct mount *mnt; |
|
int err; |
|
|
|
mnt = alloc_vfsmnt(old->mnt_devname); |
|
if (!mnt) |
|
return ERR_PTR(-ENOMEM); |
|
|
|
if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE)) |
|
mnt->mnt_group_id = 0; /* not a peer of original */ |
|
else |
|
mnt->mnt_group_id = old->mnt_group_id; |
|
|
|
if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { |
|
err = mnt_alloc_group_id(mnt); |
|
if (err) |
|
goto out_free; |
|
} |
|
|
|
mnt->mnt.mnt_flags = old->mnt.mnt_flags; |
|
mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL); |
|
|
|
atomic_inc(&sb->s_active); |
|
mnt->mnt.mnt_userns = mnt_user_ns(&old->mnt); |
|
if (!initial_idmapping(mnt->mnt.mnt_userns)) |
|
mnt->mnt.mnt_userns = get_user_ns(mnt->mnt.mnt_userns); |
|
mnt->mnt.mnt_sb = sb; |
|
mnt->mnt.mnt_root = dget(root); |
|
mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
|
mnt->mnt_parent = mnt; |
|
lock_mount_hash(); |
|
list_add_tail(&mnt->mnt_instance, &sb->s_mounts); |
|
unlock_mount_hash(); |
|
|
|
if ((flag & CL_SLAVE) || |
|
((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) { |
|
list_add(&mnt->mnt_slave, &old->mnt_slave_list); |
|
mnt->mnt_master = old; |
|
CLEAR_MNT_SHARED(mnt); |
|
} else if (!(flag & CL_PRIVATE)) { |
|
if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) |
|
list_add(&mnt->mnt_share, &old->mnt_share); |
|
if (IS_MNT_SLAVE(old)) |
|
list_add(&mnt->mnt_slave, &old->mnt_slave); |
|
mnt->mnt_master = old->mnt_master; |
|
} else { |
|
CLEAR_MNT_SHARED(mnt); |
|
} |
|
if (flag & CL_MAKE_SHARED) |
|
set_mnt_shared(mnt); |
|
|
|
/* stick the duplicate mount on the same expiry list |
|
* as the original if that was on one */ |
|
if (flag & CL_EXPIRE) { |
|
if (!list_empty(&old->mnt_expire)) |
|
list_add(&mnt->mnt_expire, &old->mnt_expire); |
|
} |
|
|
|
return mnt; |
|
|
|
out_free: |
|
mnt_free_id(mnt); |
|
free_vfsmnt(mnt); |
|
return ERR_PTR(err); |
|
} |
|
|
|
static void cleanup_mnt(struct mount *mnt) |
|
{ |
|
struct hlist_node *p; |
|
struct mount *m; |
|
/* |
|
* The warning here probably indicates that somebody messed |
|
* up a mnt_want/drop_write() pair. If this happens, the |
|
* filesystem was probably unable to make r/w->r/o transitions. |
|
* The locking used to deal with mnt_count decrement provides barriers, |
|
* so mnt_get_writers() below is safe. |
|
*/ |
|
WARN_ON(mnt_get_writers(mnt)); |
|
if (unlikely(mnt->mnt_pins.first)) |
|
mnt_pin_kill(mnt); |
|
hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) { |
|
hlist_del(&m->mnt_umount); |
|
mntput(&m->mnt); |
|
} |
|
fsnotify_vfsmount_delete(&mnt->mnt); |
|
dput(mnt->mnt.mnt_root); |
|
deactivate_super(mnt->mnt.mnt_sb); |
|
mnt_free_id(mnt); |
|
call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt); |
|
} |
|
|
|
static void __cleanup_mnt(struct rcu_head *head) |
|
{ |
|
cleanup_mnt(container_of(head, struct mount, mnt_rcu)); |
|
} |
|
|
|
static LLIST_HEAD(delayed_mntput_list); |
|
static void delayed_mntput(struct work_struct *unused) |
|
{ |
|
struct llist_node *node = llist_del_all(&delayed_mntput_list); |
|
struct mount *m, *t; |
|
|
|
llist_for_each_entry_safe(m, t, node, mnt_llist) |
|
cleanup_mnt(m); |
|
} |
|
static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput); |
|
|
|
static void mntput_no_expire(struct mount *mnt) |
|
{ |
|
LIST_HEAD(list); |
|
int count; |
|
|
|
rcu_read_lock(); |
|
if (likely(READ_ONCE(mnt->mnt_ns))) { |
|
/* |
|
* Since we don't do lock_mount_hash() here, |
|
* ->mnt_ns can change under us. However, if it's |
|
* non-NULL, then there's a reference that won't |
|
* be dropped until after an RCU delay done after |
|
* turning ->mnt_ns NULL. So if we observe it |
|
* non-NULL under rcu_read_lock(), the reference |
|
* we are dropping is not the final one. |
|
*/ |
|
mnt_add_count(mnt, -1); |
|
rcu_read_unlock(); |
|
return; |
|
} |
|
lock_mount_hash(); |
|
/* |
|
* make sure that if __legitimize_mnt() has not seen us grab |
|
* mount_lock, we'll see their refcount increment here. |
|
*/ |
|
smp_mb(); |
|
mnt_add_count(mnt, -1); |
|
count = mnt_get_count(mnt); |
|
if (count != 0) { |
|
WARN_ON(count < 0); |
|
rcu_read_unlock(); |
|
unlock_mount_hash(); |
|
return; |
|
} |
|
if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) { |
|
rcu_read_unlock(); |
|
unlock_mount_hash(); |
|
return; |
|
} |
|
mnt->mnt.mnt_flags |= MNT_DOOMED; |
|
rcu_read_unlock(); |
|
|
|
list_del(&mnt->mnt_instance); |
|
|
|
if (unlikely(!list_empty(&mnt->mnt_mounts))) { |
|
struct mount *p, *tmp; |
|
list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) { |
|
__put_mountpoint(unhash_mnt(p), &list); |
|
hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children); |
|
} |
|
} |
|
unlock_mount_hash(); |
|
shrink_dentry_list(&list); |
|
|
|
if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) { |
|
struct task_struct *task = current; |
|
if (likely(!(task->flags & PF_KTHREAD))) { |
|
init_task_work(&mnt->mnt_rcu, __cleanup_mnt); |
|
if (!task_work_add(task, &mnt->mnt_rcu, TWA_RESUME)) |
|
return; |
|
} |
|
if (llist_add(&mnt->mnt_llist, &delayed_mntput_list)) |
|
schedule_delayed_work(&delayed_mntput_work, 1); |
|
return; |
|
} |
|
cleanup_mnt(mnt); |
|
} |
|
|
|
void mntput(struct vfsmount *mnt) |
|
{ |
|
if (mnt) { |
|
struct mount *m = real_mount(mnt); |
|
/* avoid cacheline pingpong, hope gcc doesn't get "smart" */ |
|
if (unlikely(m->mnt_expiry_mark)) |
|
m->mnt_expiry_mark = 0; |
|
mntput_no_expire(m); |
|
} |
|
} |
|
EXPORT_SYMBOL(mntput); |
|
|
|
struct vfsmount *mntget(struct vfsmount *mnt) |
|
{ |
|
if (mnt) |
|
mnt_add_count(real_mount(mnt), 1); |
|
return mnt; |
|
} |
|
EXPORT_SYMBOL(mntget); |
|
|
|
/** |
|
* path_is_mountpoint() - Check if path is a mount in the current namespace. |
|
* @path: path to check |
|
* |
|
* d_mountpoint() can only be used reliably to establish if a dentry is |
|
* not mounted in any namespace and that common case is handled inline. |
|
* d_mountpoint() isn't aware of the possibility there may be multiple |
|
* mounts using a given dentry in a different namespace. This function |
|
* checks if the passed in path is a mountpoint rather than the dentry |
|
* alone. |
|
*/ |
|
bool path_is_mountpoint(const struct path *path) |
|
{ |
|
unsigned seq; |
|
bool res; |
|
|
|
if (!d_mountpoint(path->dentry)) |
|
return false; |
|
|
|
rcu_read_lock(); |
|
do { |
|
seq = read_seqbegin(&mount_lock); |
|
res = __path_is_mountpoint(path); |
|
} while (read_seqretry(&mount_lock, seq)); |
|
rcu_read_unlock(); |
|
|
|
return res; |
|
} |
|
EXPORT_SYMBOL(path_is_mountpoint); |
|
|
|
struct vfsmount *mnt_clone_internal(const struct path *path) |
|
{ |
|
struct mount *p; |
|
p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE); |
|
if (IS_ERR(p)) |
|
return ERR_CAST(p); |
|
p->mnt.mnt_flags |= MNT_INTERNAL; |
|
return &p->mnt; |
|
} |
|
|
|
#ifdef CONFIG_PROC_FS |
|
static struct mount *mnt_list_next(struct mnt_namespace *ns, |
|
struct list_head *p) |
|
{ |
|
struct mount *mnt, *ret = NULL; |
|
|
|
lock_ns_list(ns); |
|
list_for_each_continue(p, &ns->list) { |
|
mnt = list_entry(p, typeof(*mnt), mnt_list); |
|
if (!mnt_is_cursor(mnt)) { |
|
ret = mnt; |
|
break; |
|
} |
|
} |
|
unlock_ns_list(ns); |
|
|
|
return ret; |
|
} |
|
|
|
/* iterator; we want it to have access to namespace_sem, thus here... */ |
|
static void *m_start(struct seq_file *m, loff_t *pos) |
|
{ |
|
struct proc_mounts *p = m->private; |
|
struct list_head *prev; |
|
|
|
down_read(&namespace_sem); |
|
if (!*pos) { |
|
prev = &p->ns->list; |
|
} else { |
|
prev = &p->cursor.mnt_list; |
|
|
|
/* Read after we'd reached the end? */ |
|
if (list_empty(prev)) |
|
return NULL; |
|
} |
|
|
|
return mnt_list_next(p->ns, prev); |
|
} |
|
|
|
static void *m_next(struct seq_file *m, void *v, loff_t *pos) |
|
{ |
|
struct proc_mounts *p = m->private; |
|
struct mount *mnt = v; |
|
|
|
++*pos; |
|
return mnt_list_next(p->ns, &mnt->mnt_list); |
|
} |
|
|
|
static void m_stop(struct seq_file *m, void *v) |
|
{ |
|
struct proc_mounts *p = m->private; |
|
struct mount *mnt = v; |
|
|
|
lock_ns_list(p->ns); |
|
if (mnt) |
|
list_move_tail(&p->cursor.mnt_list, &mnt->mnt_list); |
|
else |
|
list_del_init(&p->cursor.mnt_list); |
|
unlock_ns_list(p->ns); |
|
up_read(&namespace_sem); |
|
} |
|
|
|
static int m_show(struct seq_file *m, void *v) |
|
{ |
|
struct proc_mounts *p = m->private; |
|
struct mount *r = v; |
|
return p->show(m, &r->mnt); |
|
} |
|
|
|
const struct seq_operations mounts_op = { |
|
.start = m_start, |
|
.next = m_next, |
|
.stop = m_stop, |
|
.show = m_show, |
|
}; |
|
|
|
void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor) |
|
{ |
|
down_read(&namespace_sem); |
|
lock_ns_list(ns); |
|
list_del(&cursor->mnt_list); |
|
unlock_ns_list(ns); |
|
up_read(&namespace_sem); |
|
} |
|
#endif /* CONFIG_PROC_FS */ |
|
|
|
/** |
|
* may_umount_tree - check if a mount tree is busy |
|
* @m: root of mount tree |
|
* |
|
* This is called to check if a tree of mounts has any |
|
* open files, pwds, chroots or sub mounts that are |
|
* busy. |
|
*/ |
|
int may_umount_tree(struct vfsmount *m) |
|
{ |
|
struct mount *mnt = real_mount(m); |
|
int actual_refs = 0; |
|
int minimum_refs = 0; |
|
struct mount *p; |
|
BUG_ON(!m); |
|
|
|
/* write lock needed for mnt_get_count */ |
|
lock_mount_hash(); |
|
for (p = mnt; p; p = next_mnt(p, mnt)) { |
|
actual_refs += mnt_get_count(p); |
|
minimum_refs += 2; |
|
} |
|
unlock_mount_hash(); |
|
|
|
if (actual_refs > minimum_refs) |
|
return 0; |
|
|
|
return 1; |
|
} |
|
|
|
EXPORT_SYMBOL(may_umount_tree); |
|
|
|
/** |
|
* may_umount - check if a mount point is busy |
|
* @mnt: root of mount |
|
* |
|
* This is called to check if a mount point has any |
|
* open files, pwds, chroots or sub mounts. If the |
|
* mount has sub mounts this will return busy |
|
* regardless of whether the sub mounts are busy. |
|
* |
|
* Doesn't take quota and stuff into account. IOW, in some cases it will |
|
* give false negatives. The main reason why it's here is that we need |
|
* a non-destructive way to look for easily umountable filesystems. |
|
*/ |
|
int may_umount(struct vfsmount *mnt) |
|
{ |
|
int ret = 1; |
|
down_read(&namespace_sem); |
|
lock_mount_hash(); |
|
if (propagate_mount_busy(real_mount(mnt), 2)) |
|
ret = 0; |
|
unlock_mount_hash(); |
|
up_read(&namespace_sem); |
|
return ret; |
|
} |
|
|
|
EXPORT_SYMBOL(may_umount); |
|
|
|
static void namespace_unlock(void) |
|
{ |
|
struct hlist_head head; |
|
struct hlist_node *p; |
|
struct mount *m; |
|
LIST_HEAD(list); |
|
|
|
hlist_move_list(&unmounted, &head); |
|
list_splice_init(&ex_mountpoints, &list); |
|
|
|
up_write(&namespace_sem); |
|
|
|
shrink_dentry_list(&list); |
|
|
|
if (likely(hlist_empty(&head))) |
|
return; |
|
|
|
synchronize_rcu_expedited(); |
|
|
|
hlist_for_each_entry_safe(m, p, &head, mnt_umount) { |
|
hlist_del(&m->mnt_umount); |
|
mntput(&m->mnt); |
|
} |
|
} |
|
|
|
static inline void namespace_lock(void) |
|
{ |
|
down_write(&namespace_sem); |
|
} |
|
|
|
enum umount_tree_flags { |
|
UMOUNT_SYNC = 1, |
|
UMOUNT_PROPAGATE = 2, |
|
UMOUNT_CONNECTED = 4, |
|
}; |
|
|
|
static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how) |
|
{ |
|
/* Leaving mounts connected is only valid for lazy umounts */ |
|
if (how & UMOUNT_SYNC) |
|
return true; |
|
|
|
/* A mount without a parent has nothing to be connected to */ |
|
if (!mnt_has_parent(mnt)) |
|
return true; |
|
|
|
/* Because the reference counting rules change when mounts are |
|
* unmounted and connected, umounted mounts may not be |
|
* connected to mounted mounts. |
|
*/ |
|
if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) |
|
return true; |
|
|
|
/* Has it been requested that the mount remain connected? */ |
|
if (how & UMOUNT_CONNECTED) |
|
return false; |
|
|
|
/* Is the mount locked such that it needs to remain connected? */ |
|
if (IS_MNT_LOCKED(mnt)) |
|
return false; |
|
|
|
/* By default disconnect the mount */ |
|
return true; |
|
} |
|
|
|
/* |
|
* mount_lock must be held |
|
* namespace_sem must be held for write |
|
*/ |
|
static void umount_tree(struct mount *mnt, enum umount_tree_flags how) |
|
{ |
|
LIST_HEAD(tmp_list); |
|
struct mount *p; |
|
|
|
if (how & UMOUNT_PROPAGATE) |
|
propagate_mount_unlock(mnt); |
|
|
|
/* Gather the mounts to umount */ |
|
for (p = mnt; p; p = next_mnt(p, mnt)) { |
|
p->mnt.mnt_flags |= MNT_UMOUNT; |
|
list_move(&p->mnt_list, &tmp_list); |
|
} |
|
|
|
/* Hide the mounts from mnt_mounts */ |
|
list_for_each_entry(p, &tmp_list, mnt_list) { |
|
list_del_init(&p->mnt_child); |
|
} |
|
|
|
/* Add propogated mounts to the tmp_list */ |
|
if (how & UMOUNT_PROPAGATE) |
|
propagate_umount(&tmp_list); |
|
|
|
while (!list_empty(&tmp_list)) { |
|
struct mnt_namespace *ns; |
|
bool disconnect; |
|
p = list_first_entry(&tmp_list, struct mount, mnt_list); |
|
list_del_init(&p->mnt_expire); |
|
list_del_init(&p->mnt_list); |
|
ns = p->mnt_ns; |
|
if (ns) { |
|
ns->mounts--; |
|
__touch_mnt_namespace(ns); |
|
} |
|
p->mnt_ns = NULL; |
|
if (how & UMOUNT_SYNC) |
|
p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; |
|
|
|
disconnect = disconnect_mount(p, how); |
|
if (mnt_has_parent(p)) { |
|
mnt_add_count(p->mnt_parent, -1); |
|
if (!disconnect) { |
|
/* Don't forget about p */ |
|
list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts); |
|
} else { |
|
umount_mnt(p); |
|
} |
|
} |
|
change_mnt_propagation(p, MS_PRIVATE); |
|
if (disconnect) |
|
hlist_add_head(&p->mnt_umount, &unmounted); |
|
} |
|
} |
|
|
|
static void shrink_submounts(struct mount *mnt); |
|
|
|
static int do_umount_root(struct super_block *sb) |
|
{ |
|
int ret = 0; |
|
|
|
down_write(&sb->s_umount); |
|
if (!sb_rdonly(sb)) { |
|
struct fs_context *fc; |
|
|
|
fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY, |
|
SB_RDONLY); |
|
if (IS_ERR(fc)) { |
|
ret = PTR_ERR(fc); |
|
} else { |
|
ret = parse_monolithic_mount_data(fc, NULL); |
|
if (!ret) |
|
ret = reconfigure_super(fc); |
|
put_fs_context(fc); |
|
} |
|
} |
|
up_write(&sb->s_umount); |
|
return ret; |
|
} |
|
|
|
static int do_umount(struct mount *mnt, int flags) |
|
{ |
|
struct super_block *sb = mnt->mnt.mnt_sb; |
|
int retval; |
|
|
|
retval = security_sb_umount(&mnt->mnt, flags); |
|
if (retval) |
|
return retval; |
|
|
|
/* |
|
* Allow userspace to request a mountpoint be expired rather than |
|
* unmounting unconditionally. Unmount only happens if: |
|
* (1) the mark is already set (the mark is cleared by mntput()) |
|
* (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] |
|
*/ |
|
if (flags & MNT_EXPIRE) { |
|
if (&mnt->mnt == current->fs->root.mnt || |
|
flags & (MNT_FORCE | MNT_DETACH)) |
|
return -EINVAL; |
|
|
|
/* |
|
* probably don't strictly need the lock here if we examined |
|
* all race cases, but it's a slowpath. |
|
*/ |
|
lock_mount_hash(); |
|
if (mnt_get_count(mnt) != 2) { |
|
unlock_mount_hash(); |
|
return -EBUSY; |
|
} |
|
unlock_mount_hash(); |
|
|
|
if (!xchg(&mnt->mnt_expiry_mark, 1)) |
|
return -EAGAIN; |
|
} |
|
|
|
/* |
|
* If we may have to abort operations to get out of this |
|
* mount, and they will themselves hold resources we must |
|
* allow the fs to do things. In the Unix tradition of |
|
* 'Gee thats tricky lets do it in userspace' the umount_begin |
|
* might fail to complete on the first run through as other tasks |
|
* must return, and the like. Thats for the mount program to worry |
|
* about for the moment. |
|
*/ |
|
|
|
if (flags & MNT_FORCE && sb->s_op->umount_begin) { |
|
sb->s_op->umount_begin(sb); |
|
} |
|
|
|
/* |
|
* No sense to grab the lock for this test, but test itself looks |
|
* somewhat bogus. Suggestions for better replacement? |
|
* Ho-hum... In principle, we might treat that as umount + switch |
|
* to rootfs. GC would eventually take care of the old vfsmount. |
|
* Actually it makes sense, especially if rootfs would contain a |
|
* /reboot - static binary that would close all descriptors and |
|
* call reboot(9). Then init(8) could umount root and exec /reboot. |
|
*/ |
|
if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { |
|
/* |
|
* Special case for "unmounting" root ... |
|
* we just try to remount it readonly. |
|
*/ |
|
if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) |
|
return -EPERM; |
|
return do_umount_root(sb); |
|
} |
|
|
|
namespace_lock(); |
|
lock_mount_hash(); |
|
|
|
/* Recheck MNT_LOCKED with the locks held */ |
|
retval = -EINVAL; |
|
if (mnt->mnt.mnt_flags & MNT_LOCKED) |
|
goto out; |
|
|
|
event++; |
|
if (flags & MNT_DETACH) { |
|
if (!list_empty(&mnt->mnt_list)) |
|
umount_tree(mnt, UMOUNT_PROPAGATE); |
|
retval = 0; |
|
} else { |
|
shrink_submounts(mnt); |
|
retval = -EBUSY; |
|
if (!propagate_mount_busy(mnt, 2)) { |
|
if (!list_empty(&mnt->mnt_list)) |
|
umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); |
|
retval = 0; |
|
} |
|
} |
|
out: |
|
unlock_mount_hash(); |
|
namespace_unlock(); |
|
return retval; |
|
} |
|
|
|
/* |
|
* __detach_mounts - lazily unmount all mounts on the specified dentry |
|
* |
|
* During unlink, rmdir, and d_drop it is possible to loose the path |
|
* to an existing mountpoint, and wind up leaking the mount. |
|
* detach_mounts allows lazily unmounting those mounts instead of |
|
* leaking them. |
|
* |
|
* The caller may hold dentry->d_inode->i_mutex. |
|
*/ |
|
void __detach_mounts(struct dentry *dentry) |
|
{ |
|
struct mountpoint *mp; |
|
struct mount *mnt; |
|
|
|
namespace_lock(); |
|
lock_mount_hash(); |
|
mp = lookup_mountpoint(dentry); |
|
if (!mp) |
|
goto out_unlock; |
|
|
|
event++; |
|
while (!hlist_empty(&mp->m_list)) { |
|
mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list); |
|
if (mnt->mnt.mnt_flags & MNT_UMOUNT) { |
|
umount_mnt(mnt); |
|
hlist_add_head(&mnt->mnt_umount, &unmounted); |
|
} |
|
else umount_tree(mnt, UMOUNT_CONNECTED); |
|
} |
|
put_mountpoint(mp); |
|
out_unlock: |
|
unlock_mount_hash(); |
|
namespace_unlock(); |
|
} |
|
|
|
/* |
|
* Is the caller allowed to modify his namespace? |
|
*/ |
|
bool may_mount(void) |
|
{ |
|
return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); |
|
} |
|
|
|
static void warn_mandlock(void) |
|
{ |
|
pr_warn_once("=======================================================\n" |
|
"WARNING: The mand mount option has been deprecated and\n" |
|
" and is ignored by this kernel. Remove the mand\n" |
|
" option from the mount to silence this warning.\n" |
|
"=======================================================\n"); |
|
} |
|
|
|
static int can_umount(const struct path *path, int flags) |
|
{ |
|
struct mount *mnt = real_mount(path->mnt); |
|
|
|
if (!may_mount()) |
|
return -EPERM; |
|
if (path->dentry != path->mnt->mnt_root) |
|
return -EINVAL; |
|
if (!check_mnt(mnt)) |
|
return -EINVAL; |
|
if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */ |
|
return -EINVAL; |
|
if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN)) |
|
return -EPERM; |
|
return 0; |
|
} |
|
|
|
// caller is responsible for flags being sane |
|
int path_umount(struct path *path, int flags) |
|
{ |
|
struct mount *mnt = real_mount(path->mnt); |
|
int ret; |
|
|
|
ret = can_umount(path, flags); |
|
if (!ret) |
|
ret = do_umount(mnt, flags); |
|
|
|
/* we mustn't call path_put() as that would clear mnt_expiry_mark */ |
|
dput(path->dentry); |
|
mntput_no_expire(mnt); |
|
return ret; |
|
} |
|
|
|
static int ksys_umount(char __user *name, int flags) |
|
{ |
|
int lookup_flags = LOOKUP_MOUNTPOINT; |
|
struct path path; |
|
int ret; |
|
|
|
// basic validity checks done first |
|
if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) |
|
return -EINVAL; |
|
|
|
if (!(flags & UMOUNT_NOFOLLOW)) |
|
lookup_flags |= LOOKUP_FOLLOW; |
|
ret = user_path_at(AT_FDCWD, name, lookup_flags, &path); |
|
if (ret) |
|
return ret; |
|
return path_umount(&path, flags); |
|
} |
|
|
|
SYSCALL_DEFINE2(umount, char __user *, name, int, flags) |
|
{ |
|
return ksys_umount(name, flags); |
|
} |
|
|
|
#ifdef __ARCH_WANT_SYS_OLDUMOUNT |
|
|
|
/* |
|
* The 2.0 compatible umount. No flags. |
|
*/ |
|
SYSCALL_DEFINE1(oldumount, char __user *, name) |
|
{ |
|
return ksys_umount(name, 0); |
|
} |
|
|
|
#endif |
|
|
|
static bool is_mnt_ns_file(struct dentry *dentry) |
|
{ |
|
/* Is this a proxy for a mount namespace? */ |
|
return dentry->d_op == &ns_dentry_operations && |
|
dentry->d_fsdata == &mntns_operations; |
|
} |
|
|
|
static struct mnt_namespace *to_mnt_ns(struct ns_common *ns) |
|
{ |
|
return container_of(ns, struct mnt_namespace, ns); |
|
} |
|
|
|
struct ns_common *from_mnt_ns(struct mnt_namespace *mnt) |
|
{ |
|
return &mnt->ns; |
|
} |
|
|
|
static bool mnt_ns_loop(struct dentry *dentry) |
|
{ |
|
/* Could bind mounting the mount namespace inode cause a |
|
* mount namespace loop? |
|
*/ |
|
struct mnt_namespace *mnt_ns; |
|
if (!is_mnt_ns_file(dentry)) |
|
return false; |
|
|
|
mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode)); |
|
return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; |
|
} |
|
|
|
struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, |
|
int flag) |
|
{ |
|
struct mount *res, *p, *q, *r, *parent; |
|
|
|
if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt)) |
|
return ERR_PTR(-EINVAL); |
|
|
|
if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) |
|
return ERR_PTR(-EINVAL); |
|
|
|
res = q = clone_mnt(mnt, dentry, flag); |
|
if (IS_ERR(q)) |
|
return q; |
|
|
|
q->mnt_mountpoint = mnt->mnt_mountpoint; |
|
|
|
p = mnt; |
|
list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { |
|
struct mount *s; |
|
if (!is_subdir(r->mnt_mountpoint, dentry)) |
|
continue; |
|
|
|
for (s = r; s; s = next_mnt(s, r)) { |
|
if (!(flag & CL_COPY_UNBINDABLE) && |
|
IS_MNT_UNBINDABLE(s)) { |
|
if (s->mnt.mnt_flags & MNT_LOCKED) { |
|
/* Both unbindable and locked. */ |
|
q = ERR_PTR(-EPERM); |
|
goto out; |
|
} else { |
|
s = skip_mnt_tree(s); |
|
continue; |
|
} |
|
} |
|
if (!(flag & CL_COPY_MNT_NS_FILE) && |
|
is_mnt_ns_file(s->mnt.mnt_root)) { |
|
s = skip_mnt_tree(s); |
|
continue; |
|
} |
|
while (p != s->mnt_parent) { |
|
p = p->mnt_parent; |
|
q = q->mnt_parent; |
|
} |
|
p = s; |
|
parent = q; |
|
q = clone_mnt(p, p->mnt.mnt_root, flag); |
|
if (IS_ERR(q)) |
|
goto out; |
|
lock_mount_hash(); |
|
list_add_tail(&q->mnt_list, &res->mnt_list); |
|
attach_mnt(q, parent, p->mnt_mp); |
|
unlock_mount_hash(); |
|
} |
|
} |
|
return res; |
|
out: |
|
if (res) { |
|
lock_mount_hash(); |
|
umount_tree(res, UMOUNT_SYNC); |
|
unlock_mount_hash(); |
|
} |
|
return q; |
|
} |
|
|
|
/* Caller should check returned pointer for errors */ |
|
|
|
struct vfsmount *collect_mounts(const struct path *path) |
|
{ |
|
struct mount *tree; |
|
namespace_lock(); |
|
if (!check_mnt(real_mount(path->mnt))) |
|
tree = ERR_PTR(-EINVAL); |
|
else |
|
tree = copy_tree(real_mount(path->mnt), path->dentry, |
|
CL_COPY_ALL | CL_PRIVATE); |
|
namespace_unlock(); |
|
if (IS_ERR(tree)) |
|
return ERR_CAST(tree); |
|
return &tree->mnt; |
|
} |
|
|
|
static void free_mnt_ns(struct mnt_namespace *); |
|
static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool); |
|
|
|
void dissolve_on_fput(struct vfsmount *mnt) |
|
{ |
|
struct mnt_namespace *ns; |
|
namespace_lock(); |
|
lock_mount_hash(); |
|
ns = real_mount(mnt)->mnt_ns; |
|
if (ns) { |
|
if (is_anon_ns(ns)) |
|
umount_tree(real_mount(mnt), UMOUNT_CONNECTED); |
|
else |
|
ns = NULL; |
|
} |
|
unlock_mount_hash(); |
|
namespace_unlock(); |
|
if (ns) |
|
free_mnt_ns(ns); |
|
} |
|
|
|
void drop_collected_mounts(struct vfsmount *mnt) |
|
{ |
|
namespace_lock(); |
|
lock_mount_hash(); |
|
umount_tree(real_mount(mnt), 0); |
|
unlock_mount_hash(); |
|
namespace_unlock(); |
|
} |
|
|
|
static bool has_locked_children(struct mount *mnt, struct dentry *dentry) |
|
{ |
|
struct mount *child; |
|
|
|
list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { |
|
if (!is_subdir(child->mnt_mountpoint, dentry)) |
|
continue; |
|
|
|
if (child->mnt.mnt_flags & MNT_LOCKED) |
|
return true; |
|
} |
|
return false; |
|
} |
|
|
|
/** |
|
* clone_private_mount - create a private clone of a path |
|
* @path: path to clone |
|
* |
|
* This creates a new vfsmount, which will be the clone of @path. The new mount |
|
* will not be attached anywhere in the namespace and will be private (i.e. |
|
* changes to the originating mount won't be propagated into this). |
|
* |
|
* Release with mntput(). |
|
*/ |
|
struct vfsmount *clone_private_mount(const struct path *path) |
|
{ |
|
struct mount *old_mnt = real_mount(path->mnt); |
|
struct mount *new_mnt; |
|
|
|
down_read(&namespace_sem); |
|
if (IS_MNT_UNBINDABLE(old_mnt)) |
|
goto invalid; |
|
|
|
if (!check_mnt(old_mnt)) |
|
goto invalid; |
|
|
|
if (has_locked_children(old_mnt, path->dentry)) |
|
goto invalid; |
|
|
|
new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE); |
|
up_read(&namespace_sem); |
|
|
|
if (IS_ERR(new_mnt)) |
|
return ERR_CAST(new_mnt); |
|
|
|
/* Longterm mount to be removed by kern_unmount*() */ |
|
new_mnt->mnt_ns = MNT_NS_INTERNAL; |
|
|
|
return &new_mnt->mnt; |
|
|
|
invalid: |
|
up_read(&namespace_sem); |
|
return ERR_PTR(-EINVAL); |
|
} |
|
EXPORT_SYMBOL_GPL(clone_private_mount); |
|
|
|
int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, |
|
struct vfsmount *root) |
|
{ |
|
struct mount *mnt; |
|
int res = f(root, arg); |
|
if (res) |
|
return res; |
|
list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { |
|
res = f(&mnt->mnt, arg); |
|
if (res) |
|
return res; |
|
} |
|
return 0; |
|
} |
|
|
|
static void lock_mnt_tree(struct mount *mnt) |
|
{ |
|
struct mount *p; |
|
|
|
for (p = mnt; p; p = next_mnt(p, mnt)) { |
|
int flags = p->mnt.mnt_flags; |
|
/* Don't allow unprivileged users to change mount flags */ |
|
flags |= MNT_LOCK_ATIME; |
|
|
|
if (flags & MNT_READONLY) |
|
flags |= MNT_LOCK_READONLY; |
|
|
|
if (flags & MNT_NODEV) |
|
flags |= MNT_LOCK_NODEV; |
|
|
|
if (flags & MNT_NOSUID) |
|
flags |= MNT_LOCK_NOSUID; |
|
|
|
if (flags & MNT_NOEXEC) |
|
flags |= MNT_LOCK_NOEXEC; |
|
/* Don't allow unprivileged users to reveal what is under a mount */ |
|
if (list_empty(&p->mnt_expire)) |
|
flags |= MNT_LOCKED; |
|
p->mnt.mnt_flags = flags; |
|
} |
|
} |
|
|
|
static void cleanup_group_ids(struct mount *mnt, struct mount *end) |
|
{ |
|
struct mount *p; |
|
|
|
for (p = mnt; p != end; p = next_mnt(p, mnt)) { |
|
if (p->mnt_group_id && !IS_MNT_SHARED(p)) |
|
mnt_release_group_id(p); |
|
} |
|
} |
|
|
|
static int invent_group_ids(struct mount *mnt, bool recurse) |
|
{ |
|
struct mount *p; |
|
|
|
for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { |
|
if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { |
|
int err = mnt_alloc_group_id(p); |
|
if (err) { |
|
cleanup_group_ids(mnt, p); |
|
return err; |
|
} |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
int count_mounts(struct mnt_namespace *ns, struct mount *mnt) |
|
{ |
|
unsigned int max = READ_ONCE(sysctl_mount_max); |
|
unsigned int mounts = 0; |
|
struct mount *p; |
|
|
|
if (ns->mounts >= max) |
|
return -ENOSPC; |
|
max -= ns->mounts; |
|
if (ns->pending_mounts >= max) |
|
return -ENOSPC; |
|
max -= ns->pending_mounts; |
|
|
|
for (p = mnt; p; p = next_mnt(p, mnt)) |
|
mounts++; |
|
|
|
if (mounts > max) |
|
return -ENOSPC; |
|
|
|
ns->pending_mounts += mounts; |
|
return 0; |
|
} |
|
|
|
/* |
|
* @source_mnt : mount tree to be attached |
|
* @nd : place the mount tree @source_mnt is attached |
|
* @parent_nd : if non-null, detach the source_mnt from its parent and |
|
* store the parent mount and mountpoint dentry. |
|
* (done when source_mnt is moved) |
|
* |
|
* NOTE: in the table below explains the semantics when a source mount |
|
* of a given type is attached to a destination mount of a given type. |
|
* --------------------------------------------------------------------------- |
|
* | BIND MOUNT OPERATION | |
|
* |************************************************************************** |
|
* | source-->| shared | private | slave | unbindable | |
|
* | dest | | | | | |
|
* | | | | | | | |
|
* | v | | | | | |
|
* |************************************************************************** |
|
* | shared | shared (++) | shared (+) | shared(+++)| invalid | |
|
* | | | | | | |
|
* |non-shared| shared (+) | private | slave (*) | invalid | |
|
* *************************************************************************** |
|
* A bind operation clones the source mount and mounts the clone on the |
|
* destination mount. |
|
* |
|
* (++) the cloned mount is propagated to all the mounts in the propagation |
|
* tree of the destination mount and the cloned mount is added to |
|
* the peer group of the source mount. |
|
* (+) the cloned mount is created under the destination mount and is marked |
|
* as shared. The cloned mount is added to the peer group of the source |
|
* mount. |
|
* (+++) the mount is propagated to all the mounts in the propagation tree |
|
* of the destination mount and the cloned mount is made slave |
|
* of the same master as that of the source mount. The cloned mount |
|
* is marked as 'shared and slave'. |
|
* (*) the cloned mount is made a slave of the same master as that of the |
|
* source mount. |
|
* |
|
* --------------------------------------------------------------------------- |
|
* | MOVE MOUNT OPERATION | |
|
* |************************************************************************** |
|
* | source-->| shared | private | slave | unbindable | |
|
* | dest | | | | | |
|
* | | | | | | | |
|
* | v | | | | | |
|
* |************************************************************************** |
|
* | shared | shared (+) | shared (+) | shared(+++) | invalid | |
|
* | | | | | | |
|
* |non-shared| shared (+*) | private | slave (*) | unbindable | |
|
* *************************************************************************** |
|
* |
|
* (+) the mount is moved to the destination. And is then propagated to |
|
* all the mounts in the propagation tree of the destination mount. |
|
* (+*) the mount is moved to the destination. |
|
* (+++) the mount is moved to the destination and is then propagated to |
|
* all the mounts belonging to the destination mount's propagation tree. |
|
* the mount is marked as 'shared and slave'. |
|
* (*) the mount continues to be a slave at the new location. |
|
* |
|
* if the source mount is a tree, the operations explained above is |
|
* applied to each mount in the tree. |
|
* Must be called without spinlocks held, since this function can sleep |
|
* in allocations. |
|
*/ |
|
static int attach_recursive_mnt(struct mount *source_mnt, |
|
struct mount *dest_mnt, |
|
struct mountpoint *dest_mp, |
|
bool moving) |
|
{ |
|
struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; |
|
HLIST_HEAD(tree_list); |
|
struct mnt_namespace *ns = dest_mnt->mnt_ns; |
|
struct mountpoint *smp; |
|
struct mount *child, *p; |
|
struct hlist_node *n; |
|
int err; |
|
|
|
/* Preallocate a mountpoint in case the new mounts need |
|
* to be tucked under other mounts. |
|
*/ |
|
smp = get_mountpoint(source_mnt->mnt.mnt_root); |
|
if (IS_ERR(smp)) |
|
return PTR_ERR(smp); |
|
|
|
/* Is there space to add these mounts to the mount namespace? */ |
|
if (!moving) { |
|
err = count_mounts(ns, source_mnt); |
|
if (err) |
|
goto out; |
|
} |
|
|
|
if (IS_MNT_SHARED(dest_mnt)) { |
|
err = invent_group_ids(source_mnt, true); |
|
if (err) |
|
goto out; |
|
err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); |
|
lock_mount_hash(); |
|
if (err) |
|
goto out_cleanup_ids; |
|
for (p = source_mnt; p; p = next_mnt(p, source_mnt)) |
|
set_mnt_shared(p); |
|
} else { |
|
lock_mount_hash(); |
|
} |
|
if (moving) { |
|
unhash_mnt(source_mnt); |
|
attach_mnt(source_mnt, dest_mnt, dest_mp); |
|
touch_mnt_namespace(source_mnt->mnt_ns); |
|
} else { |
|
if (source_mnt->mnt_ns) { |
|
/* move from anon - the caller will destroy */ |
|
list_del_init(&source_mnt->mnt_ns->list); |
|
} |
|
mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); |
|
commit_tree(source_mnt); |
|
} |
|
|
|
hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) { |
|
struct mount *q; |
|
hlist_del_init(&child->mnt_hash); |
|
q = __lookup_mnt(&child->mnt_parent->mnt, |
|
child->mnt_mountpoint); |
|
if (q) |
|
mnt_change_mountpoint(child, smp, q); |
|
/* Notice when we are propagating across user namespaces */ |
|
if (child->mnt_parent->mnt_ns->user_ns != user_ns) |
|
lock_mnt_tree(child); |
|
child->mnt.mnt_flags &= ~MNT_LOCKED; |
|
commit_tree(child); |
|
} |
|
put_mountpoint(smp); |
|
unlock_mount_hash(); |
|
|
|
return 0; |
|
|
|
out_cleanup_ids: |
|
while (!hlist_empty(&tree_list)) { |
|
child = hlist_entry(tree_list.first, struct mount, mnt_hash); |
|
child->mnt_parent->mnt_ns->pending_mounts = 0; |
|
umount_tree(child, UMOUNT_SYNC); |
|
} |
|
unlock_mount_hash(); |
|
cleanup_group_ids(source_mnt, NULL); |
|
out: |
|
ns->pending_mounts = 0; |
|
|
|
read_seqlock_excl(&mount_lock); |
|
put_mountpoint(smp); |
|
read_sequnlock_excl(&mount_lock); |
|
|
|
return err; |
|
} |
|
|
|
static struct mountpoint *lock_mount(struct path *path) |
|
{ |
|
struct vfsmount *mnt; |
|
struct dentry *dentry = path->dentry; |
|
retry: |
|
inode_lock(dentry->d_inode); |
|
if (unlikely(cant_mount(dentry))) { |
|
inode_unlock(dentry->d_inode); |
|
return ERR_PTR(-ENOENT); |
|
} |
|
namespace_lock(); |
|
mnt = lookup_mnt(path); |
|
if (likely(!mnt)) { |
|
struct mountpoint *mp = get_mountpoint(dentry); |
|
if (IS_ERR(mp)) { |
|
namespace_unlock(); |
|
inode_unlock(dentry->d_inode); |
|
return mp; |
|
} |
|
return mp; |
|
} |
|
namespace_unlock(); |
|
inode_unlock(path->dentry->d_inode); |
|
path_put(path); |
|
path->mnt = mnt; |
|
dentry = path->dentry = dget(mnt->mnt_root); |
|
goto retry; |
|
} |
|
|
|
static void unlock_mount(struct mountpoint *where) |
|
{ |
|
struct dentry *dentry = where->m_dentry; |
|
|
|
read_seqlock_excl(&mount_lock); |
|
put_mountpoint(where); |
|
read_sequnlock_excl(&mount_lock); |
|
|
|
namespace_unlock(); |
|
inode_unlock(dentry->d_inode); |
|
} |
|
|
|
static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp) |
|
{ |
|
if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER) |
|
return -EINVAL; |
|
|
|
if (d_is_dir(mp->m_dentry) != |
|
d_is_dir(mnt->mnt.mnt_root)) |
|
return -ENOTDIR; |
|
|
|
return attach_recursive_mnt(mnt, p, mp, false); |
|
} |
|
|
|
/* |
|
* Sanity check the flags to change_mnt_propagation. |
|
*/ |
|
|
|
static int flags_to_propagation_type(int ms_flags) |
|
{ |
|
int type = ms_flags & ~(MS_REC | MS_SILENT); |
|
|
|
/* Fail if any non-propagation flags are set */ |
|
if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
|
return 0; |
|
/* Only one propagation flag should be set */ |
|
if (!is_power_of_2(type)) |
|
return 0; |
|
return type; |
|
} |
|
|
|
/* |
|
* recursively change the type of the mountpoint. |
|
*/ |
|
static int do_change_type(struct path *path, int ms_flags) |
|
{ |
|
struct mount *m; |
|
struct mount *mnt = real_mount(path->mnt); |
|
int recurse = ms_flags & MS_REC; |
|
int type; |
|
int err = 0; |
|
|
|
if (path->dentry != path->mnt->mnt_root) |
|
return -EINVAL; |
|
|
|
type = flags_to_propagation_type(ms_flags); |
|
if (!type) |
|
return -EINVAL; |
|
|
|
namespace_lock(); |
|
if (type == MS_SHARED) { |
|
err = invent_group_ids(mnt, recurse); |
|
if (err) |
|
goto out_unlock; |
|
} |
|
|
|
lock_mount_hash(); |
|
for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) |
|
change_mnt_propagation(m, type); |
|
unlock_mount_hash(); |
|
|
|
out_unlock: |
|
namespace_unlock(); |
|
return err; |
|
} |
|
|
|
static struct mount *__do_loopback(struct path *old_path, int recurse) |
|
{ |
|
struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt); |
|
|
|
if (IS_MNT_UNBINDABLE(old)) |
|
return mnt; |
|
|
|
if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations) |
|
return mnt; |
|
|
|
if (!recurse && has_locked_children(old, old_path->dentry)) |
|
return mnt; |
|
|
|
if (recurse) |
|
mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE); |
|
else |
|
mnt = clone_mnt(old, old_path->dentry, 0); |
|
|
|
if (!IS_ERR(mnt)) |
|
mnt->mnt.mnt_flags &= ~MNT_LOCKED; |
|
|
|
return mnt; |
|
} |
|
|
|
/* |
|
* do loopback mount. |
|
*/ |
|
static int do_loopback(struct path *path, const char *old_name, |
|
int recurse) |
|
{ |
|
struct path old_path; |
|
struct mount *mnt = NULL, *parent; |
|
struct mountpoint *mp; |
|
int err; |
|
if (!old_name || !*old_name) |
|
return -EINVAL; |
|
err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); |
|
if (err) |
|
return err; |
|
|
|
err = -EINVAL; |
|
if (mnt_ns_loop(old_path.dentry)) |
|
goto out; |
|
|
|
mp = lock_mount(path); |
|
if (IS_ERR(mp)) { |
|
err = PTR_ERR(mp); |
|
goto out; |
|
} |
|
|
|
parent = real_mount(path->mnt); |
|
if (!check_mnt(parent)) |
|
goto out2; |
|
|
|
mnt = __do_loopback(&old_path, recurse); |
|
if (IS_ERR(mnt)) { |
|
err = PTR_ERR(mnt); |
|
goto out2; |
|
} |
|
|
|
err = graft_tree(mnt, parent, mp); |
|
if (err) { |
|
lock_mount_hash(); |
|
umount_tree(mnt, UMOUNT_SYNC); |
|
unlock_mount_hash(); |
|
} |
|
out2: |
|
unlock_mount(mp); |
|
out: |
|
path_put(&old_path); |
|
return err; |
|
} |
|
|
|
static struct file *open_detached_copy(struct path *path, bool recursive) |
|
{ |
|
struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; |
|
struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true); |
|
struct mount *mnt, *p; |
|
struct file *file; |
|
|
|
if (IS_ERR(ns)) |
|
return ERR_CAST(ns); |
|
|
|
namespace_lock(); |
|
mnt = __do_loopback(path, recursive); |
|
if (IS_ERR(mnt)) { |
|
namespace_unlock(); |
|
free_mnt_ns(ns); |
|
return ERR_CAST(mnt); |
|
} |
|
|
|
lock_mount_hash(); |
|
for (p = mnt; p; p = next_mnt(p, mnt)) { |
|
p->mnt_ns = ns; |
|
ns->mounts++; |
|
} |
|
ns->root = mnt; |
|
list_add_tail(&ns->list, &mnt->mnt_list); |
|
mntget(&mnt->mnt); |
|
unlock_mount_hash(); |
|
namespace_unlock(); |
|
|
|
mntput(path->mnt); |
|
path->mnt = &mnt->mnt; |
|
file = dentry_open(path, O_PATH, current_cred()); |
|
if (IS_ERR(file)) |
|
dissolve_on_fput(path->mnt); |
|
else |
|
file->f_mode |= FMODE_NEED_UNMOUNT; |
|
return file; |
|
} |
|
|
|
SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags) |
|
{ |
|
struct file *file; |
|
struct path path; |
|
int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW; |
|
bool detached = flags & OPEN_TREE_CLONE; |
|
int error; |
|
int fd; |
|
|
|
BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC); |
|
|
|
if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE | |
|
AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE | |
|
OPEN_TREE_CLOEXEC)) |
|
return -EINVAL; |
|
|
|
if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE) |
|
return -EINVAL; |
|
|
|
if (flags & AT_NO_AUTOMOUNT) |
|
lookup_flags &= ~LOOKUP_AUTOMOUNT; |
|
if (flags & AT_SYMLINK_NOFOLLOW) |
|
lookup_flags &= ~LOOKUP_FOLLOW; |
|
if (flags & AT_EMPTY_PATH) |
|
lookup_flags |= LOOKUP_EMPTY; |
|
|
|
if (detached && !may_mount()) |
|
return -EPERM; |
|
|
|
fd = get_unused_fd_flags(flags & O_CLOEXEC); |
|
if (fd < 0) |
|
return fd; |
|
|
|
error = user_path_at(dfd, filename, lookup_flags, &path); |
|
if (unlikely(error)) { |
|
file = ERR_PTR(error); |
|
} else { |
|
if (detached) |
|
file = open_detached_copy(&path, flags & AT_RECURSIVE); |
|
else |
|
file = dentry_open(&path, O_PATH, current_cred()); |
|
path_put(&path); |
|
} |
|
if (IS_ERR(file)) { |
|
put_unused_fd(fd); |
|
return PTR_ERR(file); |
|
} |
|
fd_install(fd, file); |
|
return fd; |
|
} |
|
|
|
/* |
|
* Don't allow locked mount flags to be cleared. |
|
* |
|
* No locks need to be held here while testing the various MNT_LOCK |
|
* flags because those flags can never be cleared once they are set. |
|
*/ |
|
static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags) |
|
{ |
|
unsigned int fl = mnt->mnt.mnt_flags; |
|
|
|
if ((fl & MNT_LOCK_READONLY) && |
|
!(mnt_flags & MNT_READONLY)) |
|
return false; |
|
|
|
if ((fl & MNT_LOCK_NODEV) && |
|
!(mnt_flags & MNT_NODEV)) |
|
return false; |
|
|
|
if ((fl & MNT_LOCK_NOSUID) && |
|
!(mnt_flags & MNT_NOSUID)) |
|
return false; |
|
|
|
if ((fl & MNT_LOCK_NOEXEC) && |
|
!(mnt_flags & MNT_NOEXEC)) |
|
return false; |
|
|
|
if ((fl & MNT_LOCK_ATIME) && |
|
((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) |
|
return false; |
|
|
|
return true; |
|
} |
|
|
|
static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags) |
|
{ |
|
bool readonly_request = (mnt_flags & MNT_READONLY); |
|
|
|
if (readonly_request == __mnt_is_readonly(&mnt->mnt)) |
|
return 0; |
|
|
|
if (readonly_request) |
|
return mnt_make_readonly(mnt); |
|
|
|
mnt->mnt.mnt_flags &= ~MNT_READONLY; |
|
return 0; |
|
} |
|
|
|
static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags) |
|
{ |
|
mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK; |
|
mnt->mnt.mnt_flags = mnt_flags; |
|
touch_mnt_namespace(mnt->mnt_ns); |
|
} |
|
|
|
static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt) |
|
{ |
|
struct super_block *sb = mnt->mnt_sb; |
|
|
|
if (!__mnt_is_readonly(mnt) && |
|
(!(sb->s_iflags & SB_I_TS_EXPIRY_WARNED)) && |
|
(ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) { |
|
char *buf = (char *)__get_free_page(GFP_KERNEL); |
|
char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM); |
|
struct tm tm; |
|
|
|
time64_to_tm(sb->s_time_max, 0, &tm); |
|
|
|
pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n", |
|
sb->s_type->name, |
|
is_mounted(mnt) ? "remounted" : "mounted", |
|
mntpath, |
|
tm.tm_year+1900, (unsigned long long)sb->s_time_max); |
|
|
|
free_page((unsigned long)buf); |
|
sb->s_iflags |= SB_I_TS_EXPIRY_WARNED; |
|
} |
|
} |
|
|
|
/* |
|
* Handle reconfiguration of the mountpoint only without alteration of the |
|
* superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND |
|
* to mount(2). |
|
*/ |
|
static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags) |
|
{ |
|
struct super_block *sb = path->mnt->mnt_sb; |
|
struct mount *mnt = real_mount(path->mnt); |
|
int ret; |
|
|
|
if (!check_mnt(mnt)) |
|
return -EINVAL; |
|
|
|
if (path->dentry != mnt->mnt.mnt_root) |
|
return -EINVAL; |
|
|
|
if (!can_change_locked_flags(mnt, mnt_flags)) |
|
return -EPERM; |
|
|
|
/* |
|
* We're only checking whether the superblock is read-only not |
|
* changing it, so only take down_read(&sb->s_umount). |
|
*/ |
|
down_read(&sb->s_umount); |
|
lock_mount_hash(); |
|
ret = change_mount_ro_state(mnt, mnt_flags); |
|
if (ret == 0) |
|
set_mount_attributes(mnt, mnt_flags); |
|
unlock_mount_hash(); |
|
up_read(&sb->s_umount); |
|
|
|
mnt_warn_timestamp_expiry(path, &mnt->mnt); |
|
|
|
return ret; |
|
} |
|
|
|
/* |
|
* change filesystem flags. dir should be a physical root of filesystem. |
|
* If you've mounted a non-root directory somewhere and want to do remount |
|
* on it - tough luck. |
|
*/ |
|
static int do_remount(struct path *path, int ms_flags, int sb_flags, |
|
int mnt_flags, void *data) |
|
{ |
|
int err; |
|
struct super_block *sb = path->mnt->mnt_sb; |
|
struct mount *mnt = real_mount(path->mnt); |
|
struct fs_context *fc; |
|
|
|
if (!check_mnt(mnt)) |
|
return -EINVAL; |
|
|
|
if (path->dentry != path->mnt->mnt_root) |
|
return -EINVAL; |
|
|
|
if (!can_change_locked_flags(mnt, mnt_flags)) |
|
return -EPERM; |
|
|
|
fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK); |
|
if (IS_ERR(fc)) |
|
return PTR_ERR(fc); |
|
|
|
fc->oldapi = true; |
|
err = parse_monolithic_mount_data(fc, data); |
|
if (!err) { |
|
down_write(&sb->s_umount); |
|
err = -EPERM; |
|
if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) { |
|
err = reconfigure_super(fc); |
|
if (!err) { |
|
lock_mount_hash(); |
|
set_mount_attributes(mnt, mnt_flags); |
|
unlock_mount_hash(); |
|
} |
|
} |
|
up_write(&sb->s_umount); |
|
} |
|
|
|
mnt_warn_timestamp_expiry(path, &mnt->mnt); |
|
|
|
put_fs_context(fc); |
|
return err; |
|
} |
|
|
|
static inline int tree_contains_unbindable(struct mount *mnt) |
|
{ |
|
struct mount *p; |
|
for (p = mnt; p; p = next_mnt(p, mnt)) { |
|
if (IS_MNT_UNBINDABLE(p)) |
|
return 1; |
|
} |
|
return 0; |
|
} |
|
|
|
/* |
|
* Check that there aren't references to earlier/same mount namespaces in the |
|
* specified subtree. Such references can act as pins for mount namespaces |
|
* that aren't checked by the mount-cycle checking code, thereby allowing |
|
* cycles to be made. |
|
*/ |
|
static bool check_for_nsfs_mounts(struct mount *subtree) |
|
{ |
|
struct mount *p; |
|
bool ret = false; |
|
|
|
lock_mount_hash(); |
|
for (p = subtree; p; p = next_mnt(p, subtree)) |
|
if (mnt_ns_loop(p->mnt.mnt_root)) |
|
goto out; |
|
|
|
ret = true; |
|
out: |
|
unlock_mount_hash(); |
|
return ret; |
|
} |
|
|
|
static int do_set_group(struct path *from_path, struct path *to_path) |
|
{ |
|
struct mount *from, *to; |
|
int err; |
|
|
|
from = real_mount(from_path->mnt); |
|
to = real_mount(to_path->mnt); |
|
|
|
namespace_lock(); |
|
|
|
err = -EINVAL; |
|
/* To and From must be mounted */ |
|
if (!is_mounted(&from->mnt)) |
|
goto out; |
|
if (!is_mounted(&to->mnt)) |
|
goto out; |
|
|
|
err = -EPERM; |
|
/* We should be allowed to modify mount namespaces of both mounts */ |
|
if (!ns_capable(from->mnt_ns->user_ns, CAP_SYS_ADMIN)) |
|
goto out; |
|
if (!ns_capable(to->mnt_ns->user_ns, CAP_SYS_ADMIN)) |
|
goto out; |
|
|
|
err = -EINVAL; |
|
/* To and From paths should be mount roots */ |
|
if (from_path->dentry != from_path->mnt->mnt_root) |
|
goto out; |
|
if (to_path->dentry != to_path->mnt->mnt_root) |
|
goto out; |
|
|
|
/* Setting sharing groups is only allowed across same superblock */ |
|
if (from->mnt.mnt_sb != to->mnt.mnt_sb) |
|
goto out; |
|
|
|
/* From mount root should be wider than To mount root */ |
|
if (!is_subdir(to->mnt.mnt_root, from->mnt.mnt_root)) |
|
goto out; |
|
|
|
/* From mount should not have locked children in place of To's root */ |
|
if (has_locked_children(from, to->mnt.mnt_root)) |
|
goto out; |
|
|
|
/* Setting sharing groups is only allowed on private mounts */ |
|
if (IS_MNT_SHARED(to) || IS_MNT_SLAVE(to)) |
|
goto out; |
|
|
|
/* From should not be private */ |
|
if (!IS_MNT_SHARED(from) && !IS_MNT_SLAVE(from)) |
|
goto out; |
|
|
|
if (IS_MNT_SLAVE(from)) { |
|
struct mount *m = from->mnt_master; |
|
|
|
list_add(&to->mnt_slave, &m->mnt_slave_list); |
|
to->mnt_master = m; |
|
} |
|
|
|
if (IS_MNT_SHARED(from)) { |
|
to->mnt_group_id = from->mnt_group_id; |
|
list_add(&to->mnt_share, &from->mnt_share); |
|
lock_mount_hash(); |
|
set_mnt_shared(to); |
|
unlock_mount_hash(); |
|
} |
|
|
|
err = 0; |
|
out: |
|
namespace_unlock(); |
|
return err; |
|
} |
|
|
|
static int do_move_mount(struct path *old_path, struct path *new_path) |
|
{ |
|
struct mnt_namespace *ns; |
|
struct mount *p; |
|
struct mount *old; |
|
struct mount *parent; |
|
struct mountpoint *mp, *old_mp; |
|
int err; |
|
bool attached; |
|
|
|
mp = lock_mount(new_path); |
|
if (IS_ERR(mp)) |
|
return PTR_ERR(mp); |
|
|
|
old = real_mount(old_path->mnt); |
|
p = real_mount(new_path->mnt); |
|
parent = old->mnt_parent; |
|
attached = mnt_has_parent(old); |
|
old_mp = old->mnt_mp; |
|
ns = old->mnt_ns; |
|
|
|
err = -EINVAL; |
|
/* The mountpoint must be in our namespace. */ |
|
if (!check_mnt(p)) |
|
goto out; |
|
|
|
/* The thing moved must be mounted... */ |
|
if (!is_mounted(&old->mnt)) |
|
goto out; |
|
|
|
/* ... and either ours or the root of anon namespace */ |
|
if (!(attached ? check_mnt(old) : is_anon_ns(ns))) |
|
goto out; |
|
|
|
if (old->mnt.mnt_flags & MNT_LOCKED) |
|
goto out; |
|
|
|
if (old_path->dentry != old_path->mnt->mnt_root) |
|
goto out; |
|
|
|
if (d_is_dir(new_path->dentry) != |
|
d_is_dir(old_path->dentry)) |
|
goto out; |
|
/* |
|
* Don't move a mount residing in a shared parent. |
|
*/ |
|
if (attached && IS_MNT_SHARED(parent)) |
|
goto out; |
|
/* |
|
* Don't move a mount tree containing unbindable mounts to a destination |
|
* mount which is shared. |
|
*/ |
|
if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) |
|
goto out; |
|
err = -ELOOP; |
|
if (!check_for_nsfs_mounts(old)) |
|
goto out; |
|
for (; mnt_has_parent(p); p = p->mnt_parent) |
|
if (p == old) |
|
goto out; |
|
|
|
err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp, |
|
attached); |
|
if (err) |
|
goto out; |
|
|
|
/* if the mount is moved, it should no longer be expire |
|
* automatically */ |
|
list_del_init(&old->mnt_expire); |
|
if (attached) |
|
put_mountpoint(old_mp); |
|
out: |
|
unlock_mount(mp); |
|
if (!err) { |
|
if (attached) |
|
mntput_no_expire(parent); |
|
else |
|
free_mnt_ns(ns); |
|
} |
|
return err; |
|
} |
|
|
|
static int do_move_mount_old(struct path *path, const char *old_name) |
|
{ |
|
struct path old_path; |
|
int err; |
|
|
|
if (!old_name || !*old_name) |
|
return -EINVAL; |
|
|
|
err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
|
if (err) |
|
return err; |
|
|
|
err = do_move_mount(&old_path, path); |
|
path_put(&old_path); |
|
return err; |
|
} |
|
|
|
/* |
|
* add a mount into a namespace's mount tree |
|
*/ |
|
static int do_add_mount(struct mount *newmnt, struct mountpoint *mp, |
|
const struct path *path, int mnt_flags) |
|
{ |
|
struct mount *parent = real_mount(path->mnt); |
|
|
|
mnt_flags &= ~MNT_INTERNAL_FLAGS; |
|
|
|
if (unlikely(!check_mnt(parent))) { |
|
/* that's acceptable only for automounts done in private ns */ |
|
if (!(mnt_flags & MNT_SHRINKABLE)) |
|
return -EINVAL; |
|
/* ... and for those we'd better have mountpoint still alive */ |
|
if (!parent->mnt_ns) |
|
return -EINVAL; |
|
} |
|
|
|
/* Refuse the same filesystem on the same mount point */ |
|
if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && |
|
path->mnt->mnt_root == path->dentry) |
|
return -EBUSY; |
|
|
|
if (d_is_symlink(newmnt->mnt.mnt_root)) |
|
return -EINVAL; |
|
|
|
newmnt->mnt.mnt_flags = mnt_flags; |
|
return graft_tree(newmnt, parent, mp); |
|
} |
|
|
|
static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags); |
|
|
|
/* |
|
* Create a new mount using a superblock configuration and request it |
|
* be added to the namespace tree. |
|
*/ |
|
static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint, |
|
unsigned int mnt_flags) |
|
{ |
|
struct vfsmount *mnt; |
|
struct mountpoint *mp; |
|
struct super_block *sb = fc->root->d_sb; |
|
int error; |
|
|
|
error = security_sb_kern_mount(sb); |
|
if (!error && mount_too_revealing(sb, &mnt_flags)) |
|
error = -EPERM; |
|
|
|
if (unlikely(error)) { |
|
fc_drop_locked(fc); |
|
return error; |
|
} |
|
|
|
up_write(&sb->s_umount); |
|
|
|
mnt = vfs_create_mount(fc); |
|
if (IS_ERR(mnt)) |
|
return PTR_ERR(mnt); |
|
|
|
mnt_warn_timestamp_expiry(mountpoint, mnt); |
|
|
|
mp = lock_mount(mountpoint); |
|
if (IS_ERR(mp)) { |
|
mntput(mnt); |
|
return PTR_ERR(mp); |
|
} |
|
error = do_add_mount(real_mount(mnt), mp, mountpoint, mnt_flags); |
|
unlock_mount(mp); |
|
if (error < 0) |
|
mntput(mnt); |
|
return error; |
|
} |
|
|
|
/* |
|
* create a new mount for userspace and request it to be added into the |
|
* namespace's tree |
|
*/ |
|
static int do_new_mount(struct path *path, const char *fstype, int sb_flags, |
|
int mnt_flags, const char *name, void *data) |
|
{ |
|
struct file_system_type *type; |
|
struct fs_context *fc; |
|
const char *subtype = NULL; |
|
int err = 0; |
|
|
|
if (!fstype) |
|
return -EINVAL; |
|
|
|
type = get_fs_type(fstype); |
|
if (!type) |
|
return -ENODEV; |
|
|
|
if (type->fs_flags & FS_HAS_SUBTYPE) { |
|
subtype = strchr(fstype, '.'); |
|
if (subtype) { |
|
subtype++; |
|
if (!*subtype) { |
|
put_filesystem(type); |
|
return -EINVAL; |
|
} |
|
} |
|
} |
|
|
|
fc = fs_context_for_mount(type, sb_flags); |
|
put_filesystem(type); |
|
if (IS_ERR(fc)) |
|
return PTR_ERR(fc); |
|
|
|
if (subtype) |
|
err = vfs_parse_fs_string(fc, "subtype", |
|
subtype, strlen(subtype)); |
|
if (!err && name) |
|
err = vfs_parse_fs_string(fc, "source", name, strlen(name)); |
|
if (!err) |
|
err = parse_monolithic_mount_data(fc, data); |
|
if (!err && !mount_capable(fc)) |
|
err = -EPERM; |
|
if (!err) |
|
err = vfs_get_tree(fc); |
|
if (!err) |
|
err = do_new_mount_fc(fc, path, mnt_flags); |
|
|
|
put_fs_context(fc); |
|
return err; |
|
} |
|
|
|
int finish_automount(struct vfsmount *m, const struct path *path) |
|
{ |
|
struct dentry *dentry = path->dentry; |
|
struct mountpoint *mp; |
|
struct mount *mnt; |
|
int err; |
|
|
|
if (!m) |
|
return 0; |
|
if (IS_ERR(m)) |
|
return PTR_ERR(m); |
|
|
|
mnt = real_mount(m); |
|
/* The new mount record should have at least 2 refs to prevent it being |
|
* expired before we get a chance to add it |
|
*/ |
|
BUG_ON(mnt_get_count(mnt) < 2); |
|
|
|
if (m->mnt_sb == path->mnt->mnt_sb && |
|
m->mnt_root == dentry) { |
|
err = -ELOOP; |
|
goto discard; |
|
} |
|
|
|
/* |
|
* we don't want to use lock_mount() - in this case finding something |
|
* that overmounts our mountpoint to be means "quitely drop what we've |
|
* got", not "try to mount it on top". |
|
*/ |
|
inode_lock(dentry->d_inode); |
|
namespace_lock(); |
|
if (unlikely(cant_mount(dentry))) { |
|
err = -ENOENT; |
|
goto discard_locked; |
|
} |
|
rcu_read_lock(); |
|
if (unlikely(__lookup_mnt(path->mnt, dentry))) { |
|
rcu_read_unlock(); |
|
err = 0; |
|
goto discard_locked; |
|
} |
|
rcu_read_unlock(); |
|
mp = get_mountpoint(dentry); |
|
if (IS_ERR(mp)) { |
|
err = PTR_ERR(mp); |
|
goto discard_locked; |
|
} |
|
|
|
err = do_add_mount(mnt, mp, path, path->mnt->mnt_flags | MNT_SHRINKABLE); |
|
unlock_mount(mp); |
|
if (unlikely(err)) |
|
goto discard; |
|
mntput(m); |
|
return 0; |
|
|
|
discard_locked: |
|
namespace_unlock(); |
|
inode_unlock(dentry->d_inode); |
|
discard: |
|
/* remove m from any expiration list it may be on */ |
|
if (!list_empty(&mnt->mnt_expire)) { |
|
namespace_lock(); |
|
list_del_init(&mnt->mnt_expire); |
|
namespace_unlock(); |
|
} |
|
mntput(m); |
|
mntput(m); |
|
return err; |
|
} |
|
|
|
/** |
|
* mnt_set_expiry - Put a mount on an expiration list |
|
* @mnt: The mount to list. |
|
* @expiry_list: The list to add the mount to. |
|
*/ |
|
void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) |
|
{ |
|
namespace_lock(); |
|
|
|
list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); |
|
|
|
namespace_unlock(); |
|
} |
|
EXPORT_SYMBOL(mnt_set_expiry); |
|
|
|
/* |
|
* process a list of expirable mountpoints with the intent of discarding any |
|
* mountpoints that aren't in use and haven't been touched since last we came |
|
* here |
|
*/ |
|
void mark_mounts_for_expiry(struct list_head *mounts) |
|
{ |
|
struct mount *mnt, *next; |
|
LIST_HEAD(graveyard); |
|
|
|
if (list_empty(mounts)) |
|
return; |
|
|
|
namespace_lock(); |
|
lock_mount_hash(); |
|
|
|
/* extract from the expiration list every vfsmount that matches the |
|
* following criteria: |
|
* - only referenced by its parent vfsmount |
|
* - still marked for expiry (marked on the last call here; marks are |
|
* cleared by mntput()) |
|
*/ |
|
list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { |
|
if (!xchg(&mnt->mnt_expiry_mark, 1) || |
|
propagate_mount_busy(mnt, 1)) |
|
continue; |
|
list_move(&mnt->mnt_expire, &graveyard); |
|
} |
|
while (!list_empty(&graveyard)) { |
|
mnt = list_first_entry(&graveyard, struct mount, mnt_expire); |
|
touch_mnt_namespace(mnt->mnt_ns); |
|
umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); |
|
} |
|
unlock_mount_hash(); |
|
namespace_unlock(); |
|
} |
|
|
|
EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); |
|
|
|
/* |
|
* Ripoff of 'select_parent()' |
|
* |
|
* search the list of submounts for a given mountpoint, and move any |
|
* shrinkable submounts to the 'graveyard' list. |
|
*/ |
|
static int select_submounts(struct mount *parent, struct list_head *graveyard) |
|
{ |
|
struct mount *this_parent = parent; |
|
struct list_head *next; |
|
int found = 0; |
|
|
|
repeat: |
|
next = this_parent->mnt_mounts.next; |
|
resume: |
|
while (next != &this_parent->mnt_mounts) { |
|
struct list_head *tmp = next; |
|
struct mount *mnt = list_entry(tmp, struct mount, mnt_child); |
|
|
|
next = tmp->next; |
|
if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) |
|
continue; |
|
/* |
|
* Descend a level if the d_mounts list is non-empty. |
|
*/ |
|
if (!list_empty(&mnt->mnt_mounts)) { |
|
this_parent = mnt; |
|
goto repeat; |
|
} |
|
|
|
if (!propagate_mount_busy(mnt, 1)) { |
|
list_move_tail(&mnt->mnt_expire, graveyard); |
|
found++; |
|
} |
|
} |
|
/* |
|
* All done at this level ... ascend and resume the search |
|
*/ |
|
if (this_parent != parent) { |
|
next = this_parent->mnt_child.next; |
|
this_parent = this_parent->mnt_parent; |
|
goto resume; |
|
} |
|
return found; |
|
} |
|
|
|
/* |
|
* process a list of expirable mountpoints with the intent of discarding any |
|
* submounts of a specific parent mountpoint |
|
* |
|
* mount_lock must be held for write |
|
*/ |
|
static void shrink_submounts(struct mount *mnt) |
|
{ |
|
LIST_HEAD(graveyard); |
|
struct mount *m; |
|
|
|
/* extract submounts of 'mountpoint' from the expiration list */ |
|
while (select_submounts(mnt, &graveyard)) { |
|
while (!list_empty(&graveyard)) { |
|
m = list_first_entry(&graveyard, struct mount, |
|
mnt_expire); |
|
touch_mnt_namespace(m->mnt_ns); |
|
umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC); |
|
} |
|
} |
|
} |
|
|
|
static void *copy_mount_options(const void __user * data) |
|
{ |
|
char *copy; |
|
unsigned left, offset; |
|
|
|
if (!data) |
|
return NULL; |
|
|
|
copy = kmalloc(PAGE_SIZE, GFP_KERNEL); |
|
if (!copy) |
|
return ERR_PTR(-ENOMEM); |
|
|
|
left = copy_from_user(copy, data, PAGE_SIZE); |
|
|
|
/* |
|
* Not all architectures have an exact copy_from_user(). Resort to |
|
* byte at a time. |
|
*/ |
|
offset = PAGE_SIZE - left; |
|
while (left) { |
|
char c; |
|
if (get_user(c, (const char __user *)data + offset)) |
|
break; |
|
copy[offset] = c; |
|
left--; |
|
offset++; |
|
} |
|
|
|
if (left == PAGE_SIZE) { |
|
kfree(copy); |
|
return ERR_PTR(-EFAULT); |
|
} |
|
|
|
return copy; |
|
} |
|
|
|
static char *copy_mount_string(const void __user *data) |
|
{ |
|
return data ? strndup_user(data, PATH_MAX) : NULL; |
|
} |
|
|
|
/* |
|
* Flags is a 32-bit value that allows up to 31 non-fs dependent flags to |
|
* be given to the mount() call (ie: read-only, no-dev, no-suid etc). |
|
* |
|
* data is a (void *) that can point to any structure up to |
|
* PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent |
|
* information (or be NULL). |
|
* |
|
* Pre-0.97 versions of mount() didn't have a flags word. |
|
* When the flags word was introduced its top half was required |
|
* to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. |
|
* Therefore, if this magic number is present, it carries no information |
|
* and must be discarded. |
|
*/ |
|
int path_mount(const char *dev_name, struct path *path, |
|
const char *type_page, unsigned long flags, void *data_page) |
|
{ |
|
unsigned int mnt_flags = 0, sb_flags; |
|
int ret; |
|
|
|
/* Discard magic */ |
|
if ((flags & MS_MGC_MSK) == MS_MGC_VAL) |
|
flags &= ~MS_MGC_MSK; |
|
|
|
/* Basic sanity checks */ |
|
if (data_page) |
|
((char *)data_page)[PAGE_SIZE - 1] = 0; |
|
|
|
if (flags & MS_NOUSER) |
|
return -EINVAL; |
|
|
|
ret = security_sb_mount(dev_name, path, type_page, flags, data_page); |
|
if (ret) |
|
return ret; |
|
if (!may_mount()) |
|
return -EPERM; |
|
if (flags & SB_MANDLOCK) |
|
warn_mandlock(); |
|
|
|
/* Default to relatime unless overriden */ |
|
if (!(flags & MS_NOATIME)) |
|
mnt_flags |= MNT_RELATIME; |
|
|
|
/* Separate the per-mountpoint flags */ |
|
if (flags & MS_NOSUID) |
|
mnt_flags |= MNT_NOSUID; |
|
if (flags & MS_NODEV) |
|
mnt_flags |= MNT_NODEV; |
|
if (flags & MS_NOEXEC) |
|
mnt_flags |= MNT_NOEXEC; |
|
if (flags & MS_NOATIME) |
|
mnt_flags |= MNT_NOATIME; |
|
if (flags & MS_NODIRATIME) |
|
mnt_flags |= MNT_NODIRATIME; |
|
if (flags & MS_STRICTATIME) |
|
mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); |
|
if (flags & MS_RDONLY) |
|
mnt_flags |= MNT_READONLY; |
|
if (flags & MS_NOSYMFOLLOW) |
|
mnt_flags |= MNT_NOSYMFOLLOW; |
|
|
|
/* The default atime for remount is preservation */ |
|
if ((flags & MS_REMOUNT) && |
|
((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME | |
|
MS_STRICTATIME)) == 0)) { |
|
mnt_flags &= ~MNT_ATIME_MASK; |
|
mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK; |
|
} |
|
|
|
sb_flags = flags & (SB_RDONLY | |
|
SB_SYNCHRONOUS | |
|
SB_MANDLOCK | |
|
SB_DIRSYNC | |
|
SB_SILENT | |
|
SB_POSIXACL | |
|
SB_LAZYTIME | |
|
SB_I_VERSION); |
|
|
|
if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND)) |
|
return do_reconfigure_mnt(path, mnt_flags); |
|
if (flags & MS_REMOUNT) |
|
return do_remount(path, flags, sb_flags, mnt_flags, data_page); |
|
if (flags & MS_BIND) |
|
return do_loopback(path, dev_name, flags & MS_REC); |
|
if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
|
return do_change_type(path, flags); |
|
if (flags & MS_MOVE) |
|
return do_move_mount_old(path, dev_name); |
|
|
|
return do_new_mount(path, type_page, sb_flags, mnt_flags, dev_name, |
|
data_page); |
|
} |
|
|
|
long do_mount(const char *dev_name, const char __user *dir_name, |
|
const char *type_page, unsigned long flags, void *data_page) |
|
{ |
|
struct path path; |
|
int ret; |
|
|
|
ret = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path); |
|
if (ret) |
|
return ret; |
|
ret = path_mount(dev_name, &path, type_page, flags, data_page); |
|
path_put(&path); |
|
return ret; |
|
} |
|
|
|
static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns) |
|
{ |
|
return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES); |
|
} |
|
|
|
static void dec_mnt_namespaces(struct ucounts *ucounts) |
|
{ |
|
dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES); |
|
} |
|
|
|
static void free_mnt_ns(struct mnt_namespace *ns) |
|
{ |
|
if (!is_anon_ns(ns)) |
|
ns_free_inum(&ns->ns); |
|
dec_mnt_namespaces(ns->ucounts); |
|
put_user_ns(ns->user_ns); |
|
kfree(ns); |
|
} |
|
|
|
/* |
|
* Assign a sequence number so we can detect when we attempt to bind |
|
* mount a reference to an older mount namespace into the current |
|
* mount namespace, preventing reference counting loops. A 64bit |
|
* number incrementing at 10Ghz will take 12,427 years to wrap which |
|
* is effectively never, so we can ignore the possibility. |
|
*/ |
|
static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); |
|
|
|
static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon) |
|
{ |
|
struct mnt_namespace *new_ns; |
|
struct ucounts *ucounts; |
|
int ret; |
|
|
|
ucounts = inc_mnt_namespaces(user_ns); |
|
if (!ucounts) |
|
return ERR_PTR(-ENOSPC); |
|
|
|
new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL_ACCOUNT); |
|
if (!new_ns) { |
|
dec_mnt_namespaces(ucounts); |
|
return ERR_PTR(-ENOMEM); |
|
} |
|
if (!anon) { |
|
ret = ns_alloc_inum(&new_ns->ns); |
|
if (ret) { |
|
kfree(new_ns); |
|
dec_mnt_namespaces(ucounts); |
|
return ERR_PTR(ret); |
|
} |
|
} |
|
new_ns->ns.ops = &mntns_operations; |
|
if (!anon) |
|
new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); |
|
refcount_set(&new_ns->ns.count, 1); |
|
INIT_LIST_HEAD(&new_ns->list); |
|
init_waitqueue_head(&new_ns->poll); |
|
spin_lock_init(&new_ns->ns_lock); |
|
new_ns->user_ns = get_user_ns(user_ns); |
|
new_ns->ucounts = ucounts; |
|
return new_ns; |
|
} |
|
|
|
__latent_entropy |
|
struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, |
|
struct user_namespace *user_ns, struct fs_struct *new_fs) |
|
{ |
|
struct mnt_namespace *new_ns; |
|
struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; |
|
struct mount *p, *q; |
|
struct mount *old; |
|
struct mount *new; |
|
int copy_flags; |
|
|
|
BUG_ON(!ns); |
|
|
|
if (likely(!(flags & CLONE_NEWNS))) { |
|
get_mnt_ns(ns); |
|
return ns; |
|
} |
|
|
|
old = ns->root; |
|
|
|
new_ns = alloc_mnt_ns(user_ns, false); |
|
if (IS_ERR(new_ns)) |
|
return new_ns; |
|
|
|
namespace_lock(); |
|
/* First pass: copy the tree topology */ |
|
copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE; |
|
if (user_ns != ns->user_ns) |
|
copy_flags |= CL_SHARED_TO_SLAVE; |
|
new = copy_tree(old, old->mnt.mnt_root, copy_flags); |
|
if (IS_ERR(new)) { |
|
namespace_unlock(); |
|
free_mnt_ns(new_ns); |
|
return ERR_CAST(new); |
|
} |
|
if (user_ns != ns->user_ns) { |
|
lock_mount_hash(); |
|
lock_mnt_tree(new); |
|
unlock_mount_hash(); |
|
} |
|
new_ns->root = new; |
|
list_add_tail(&new_ns->list, &new->mnt_list); |
|
|
|
/* |
|
* Second pass: switch the tsk->fs->* elements and mark new vfsmounts |
|
* as belonging to new namespace. We have already acquired a private |
|
* fs_struct, so tsk->fs->lock is not needed. |
|
*/ |
|
p = old; |
|
q = new; |
|
while (p) { |
|
q->mnt_ns = new_ns; |
|
new_ns->mounts++; |
|
if (new_fs) { |
|
if (&p->mnt == new_fs->root.mnt) { |
|
new_fs->root.mnt = mntget(&q->mnt); |
|
rootmnt = &p->mnt; |
|
} |
|
if (&p->mnt == new_fs->pwd.mnt) { |
|
new_fs->pwd.mnt = mntget(&q->mnt); |
|
pwdmnt = &p->mnt; |
|
} |
|
} |
|
p = next_mnt(p, old); |
|
q = next_mnt(q, new); |
|
if (!q) |
|
break; |
|
while (p->mnt.mnt_root != q->mnt.mnt_root) |
|
p = next_mnt(p, old); |
|
} |
|
namespace_unlock(); |
|
|
|
if (rootmnt) |
|
mntput(rootmnt); |
|
if (pwdmnt) |
|
mntput(pwdmnt); |
|
|
|
return new_ns; |
|
} |
|
|
|
struct dentry *mount_subtree(struct vfsmount *m, const char *name) |
|
{ |
|
struct mount *mnt = real_mount(m); |
|
struct mnt_namespace *ns; |
|
struct super_block *s; |
|
struct path path; |
|
int err; |
|
|
|
ns = alloc_mnt_ns(&init_user_ns, true); |
|
if (IS_ERR(ns)) { |
|
mntput(m); |
|
return ERR_CAST(ns); |
|
} |
|
mnt->mnt_ns = ns; |
|
ns->root = mnt; |
|
ns->mounts++; |
|
list_add(&mnt->mnt_list, &ns->list); |
|
|
|
err = vfs_path_lookup(m->mnt_root, m, |
|
name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); |
|
|
|
put_mnt_ns(ns); |
|
|
|
if (err) |
|
return ERR_PTR(err); |
|
|
|
/* trade a vfsmount reference for active sb one */ |
|
s = path.mnt->mnt_sb; |
|
atomic_inc(&s->s_active); |
|
mntput(path.mnt); |
|
/* lock the sucker */ |
|
down_write(&s->s_umount); |
|
/* ... and return the root of (sub)tree on it */ |
|
return path.dentry; |
|
} |
|
EXPORT_SYMBOL(mount_subtree); |
|
|
|
SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, |
|
char __user *, type, unsigned long, flags, void __user *, data) |
|
{ |
|
int ret; |
|
char *kernel_type; |
|
char *kernel_dev; |
|
void *options; |
|
|
|
kernel_type = copy_mount_string(type); |
|
ret = PTR_ERR(kernel_type); |
|
if (IS_ERR(kernel_type)) |
|
goto out_type; |
|
|
|
kernel_dev = copy_mount_string(dev_name); |
|
ret = PTR_ERR(kernel_dev); |
|
if (IS_ERR(kernel_dev)) |
|
goto out_dev; |
|
|
|
options = copy_mount_options(data); |
|
ret = PTR_ERR(options); |
|
if (IS_ERR(options)) |
|
goto out_data; |
|
|
|
ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options); |
|
|
|
kfree(options); |
|
out_data: |
|
kfree(kernel_dev); |
|
out_dev: |
|
kfree(kernel_type); |
|
out_type: |
|
return ret; |
|
} |
|
|
|
#define FSMOUNT_VALID_FLAGS \ |
|
(MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \ |
|
MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \ |
|
MOUNT_ATTR_NOSYMFOLLOW) |
|
|
|
#define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP) |
|
|
|
#define MOUNT_SETATTR_PROPAGATION_FLAGS \ |
|
(MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED) |
|
|
|
static unsigned int attr_flags_to_mnt_flags(u64 attr_flags) |
|
{ |
|
unsigned int mnt_flags = 0; |
|
|
|
if (attr_flags & MOUNT_ATTR_RDONLY) |
|
mnt_flags |= MNT_READONLY; |
|
if (attr_flags & MOUNT_ATTR_NOSUID) |
|
mnt_flags |= MNT_NOSUID; |
|
if (attr_flags & MOUNT_ATTR_NODEV) |
|
mnt_flags |= MNT_NODEV; |
|
if (attr_flags & MOUNT_ATTR_NOEXEC) |
|
mnt_flags |= MNT_NOEXEC; |
|
if (attr_flags & MOUNT_ATTR_NODIRATIME) |
|
mnt_flags |= MNT_NODIRATIME; |
|
if (attr_flags & MOUNT_ATTR_NOSYMFOLLOW) |
|
mnt_flags |= MNT_NOSYMFOLLOW; |
|
|
|
return mnt_flags; |
|
} |
|
|
|
/* |
|
* Create a kernel mount representation for a new, prepared superblock |
|
* (specified by fs_fd) and attach to an open_tree-like file descriptor. |
|
*/ |
|
SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags, |
|
unsigned int, attr_flags) |
|
{ |
|
struct mnt_namespace *ns; |
|
struct fs_context *fc; |
|
struct file *file; |
|
struct path newmount; |
|
struct mount *mnt; |
|
struct fd f; |
|
unsigned int mnt_flags = 0; |
|
long ret; |
|
|
|
if (!may_mount()) |
|
return -EPERM; |
|
|
|
if ((flags & ~(FSMOUNT_CLOEXEC)) != 0) |
|
return -EINVAL; |
|
|
|
if (attr_flags & ~FSMOUNT_VALID_FLAGS) |
|
return -EINVAL; |
|
|
|
mnt_flags = attr_flags_to_mnt_flags(attr_flags); |
|
|
|
switch (attr_flags & MOUNT_ATTR__ATIME) { |
|
case MOUNT_ATTR_STRICTATIME: |
|
break; |
|
case MOUNT_ATTR_NOATIME: |
|
mnt_flags |= MNT_NOATIME; |
|
break; |
|
case MOUNT_ATTR_RELATIME: |
|
mnt_flags |= MNT_RELATIME; |
|
break; |
|
default: |
|
return -EINVAL; |
|
} |
|
|
|
f = fdget(fs_fd); |
|
if (!f.file) |
|
return -EBADF; |
|
|
|
ret = -EINVAL; |
|
if (f.file->f_op != &fscontext_fops) |
|
goto err_fsfd; |
|
|
|
fc = f.file->private_data; |
|
|
|
ret = mutex_lock_interruptible(&fc->uapi_mutex); |
|
if (ret < 0) |
|
goto err_fsfd; |
|
|
|
/* There must be a valid superblock or we can't mount it */ |
|
ret = -EINVAL; |
|
if (!fc->root) |
|
goto err_unlock; |
|
|
|
ret = -EPERM; |
|
if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) { |
|
pr_warn("VFS: Mount too revealing\n"); |
|
goto err_unlock; |
|
} |
|
|
|
ret = -EBUSY; |
|
if (fc->phase != FS_CONTEXT_AWAITING_MOUNT) |
|
goto err_unlock; |
|
|
|
if (fc->sb_flags & SB_MANDLOCK) |
|
warn_mandlock(); |
|
|
|
newmount.mnt = vfs_create_mount(fc); |
|
if (IS_ERR(newmount.mnt)) { |
|
ret = PTR_ERR(newmount.mnt); |
|
goto err_unlock; |
|
} |
|
newmount.dentry = dget(fc->root); |
|
newmount.mnt->mnt_flags = mnt_flags; |
|
|
|
/* We've done the mount bit - now move the file context into more or |
|
* less the same state as if we'd done an fspick(). We don't want to |
|
* do any memory allocation or anything like that at this point as we |
|
* don't want to have to handle any errors incurred. |
|
*/ |
|
vfs_clean_context(fc); |
|
|
|
ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true); |
|
if (IS_ERR(ns)) { |
|
ret = PTR_ERR(ns); |
|
goto err_path; |
|
} |
|
mnt = real_mount(newmount.mnt); |
|
mnt->mnt_ns = ns; |
|
ns->root = mnt; |
|
ns->mounts = 1; |
|
list_add(&mnt->mnt_list, &ns->list); |
|
mntget(newmount.mnt); |
|
|
|
/* Attach to an apparent O_PATH fd with a note that we need to unmount |
|
* it, not just simply put it. |
|
*/ |
|
file = dentry_open(&newmount, O_PATH, fc->cred); |
|
if (IS_ERR(file)) { |
|
dissolve_on_fput(newmount.mnt); |
|
ret = PTR_ERR(file); |
|
goto err_path; |
|
} |
|
file->f_mode |= FMODE_NEED_UNMOUNT; |
|
|
|
ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0); |
|
if (ret >= 0) |
|
fd_install(ret, file); |
|
else |
|
fput(file); |
|
|
|
err_path: |
|
path_put(&newmount); |
|
err_unlock: |
|
mutex_unlock(&fc->uapi_mutex); |
|
err_fsfd: |
|
fdput(f); |
|
return ret; |
|
} |
|
|
|
/* |
|
* Move a mount from one place to another. In combination with |
|
* fsopen()/fsmount() this is used to install a new mount and in combination |
|
* with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy |
|
* a mount subtree. |
|
* |
|
* Note the flags value is a combination of MOVE_MOUNT_* flags. |
|
*/ |
|
SYSCALL_DEFINE5(move_mount, |
|
int, from_dfd, const char __user *, from_pathname, |
|
int, to_dfd, const char __user *, to_pathname, |
|
unsigned int, flags) |
|
{ |
|
struct path from_path, to_path; |
|
unsigned int lflags; |
|
int ret = 0; |
|
|
|
if (!may_mount()) |
|
return -EPERM; |
|
|
|
if (flags & ~MOVE_MOUNT__MASK) |
|
return -EINVAL; |
|
|
|
/* If someone gives a pathname, they aren't permitted to move |
|
* from an fd that requires unmount as we can't get at the flag |
|
* to clear it afterwards. |
|
*/ |
|
lflags = 0; |
|
if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW; |
|
if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT; |
|
if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY; |
|
|
|
ret = user_path_at(from_dfd, from_pathname, lflags, &from_path); |
|
if (ret < 0) |
|
return ret; |
|
|
|
lflags = 0; |
|
if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW; |
|
if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT; |
|
if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY; |
|
|
|
ret = user_path_at(to_dfd, to_pathname, lflags, &to_path); |
|
if (ret < 0) |
|
goto out_from; |
|
|
|
ret = security_move_mount(&from_path, &to_path); |
|
if (ret < 0) |
|
goto out_to; |
|
|
|
if (flags & MOVE_MOUNT_SET_GROUP) |
|
ret = do_set_group(&from_path, &to_path); |
|
else |
|
ret = do_move_mount(&from_path, &to_path); |
|
|
|
out_to: |
|
path_put(&to_path); |
|
out_from: |
|
path_put(&from_path); |
|
return ret; |
|
} |
|
|
|
/* |
|
* Return true if path is reachable from root |
|
* |
|
* namespace_sem or mount_lock is held |
|
*/ |
|
bool is_path_reachable(struct mount *mnt, struct dentry *dentry, |
|
const struct path *root) |
|
{ |
|
while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { |
|
dentry = mnt->mnt_mountpoint; |
|
mnt = mnt->mnt_parent; |
|
} |
|
return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); |
|
} |
|
|
|
bool path_is_under(const struct path *path1, const struct path *path2) |
|
{ |
|
bool res; |
|
read_seqlock_excl(&mount_lock); |
|
res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); |
|
read_sequnlock_excl(&mount_lock); |
|
return res; |
|
} |
|
EXPORT_SYMBOL(path_is_under); |
|
|
|
/* |
|
* pivot_root Semantics: |
|
* Moves the root file system of the current process to the directory put_old, |
|
* makes new_root as the new root file system of the current process, and sets |
|
* root/cwd of all processes which had them on the current root to new_root. |
|
* |
|
* Restrictions: |
|
* The new_root and put_old must be directories, and must not be on the |
|
* same file system as the current process root. The put_old must be |
|
* underneath new_root, i.e. adding a non-zero number of /.. to the string |
|
* pointed to by put_old must yield the same directory as new_root. No other |
|
* file system may be mounted on put_old. After all, new_root is a mountpoint. |
|
* |
|
* Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. |
|
* See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives |
|
* in this situation. |
|
* |
|
* Notes: |
|
* - we don't move root/cwd if they are not at the root (reason: if something |
|
* cared enough to change them, it's probably wrong to force them elsewhere) |
|
* - it's okay to pick a root that isn't the root of a file system, e.g. |
|
* /nfs/my_root where /nfs is the mount point. It must be a mountpoint, |
|
* though, so you may need to say mount --bind /nfs/my_root /nfs/my_root |
|
* first. |
|
*/ |
|
SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, |
|
const char __user *, put_old) |
|
{ |
|
struct path new, old, root; |
|
struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent; |
|
struct mountpoint *old_mp, *root_mp; |
|
int error; |
|
|
|
if (!may_mount()) |
|
return -EPERM; |
|
|
|
error = user_path_at(AT_FDCWD, new_root, |
|
LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new); |
|
if (error) |
|
goto out0; |
|
|
|
error = user_path_at(AT_FDCWD, put_old, |
|
LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old); |
|
if (error) |
|
goto out1; |
|
|
|
error = security_sb_pivotroot(&old, &new); |
|
if (error) |
|
goto out2; |
|
|
|
get_fs_root(current->fs, &root); |
|
old_mp = lock_mount(&old); |
|
error = PTR_ERR(old_mp); |
|
if (IS_ERR(old_mp)) |
|
goto out3; |
|
|
|
error = -EINVAL; |
|
new_mnt = real_mount(new.mnt); |
|
root_mnt = real_mount(root.mnt); |
|
old_mnt = real_mount(old.mnt); |
|
ex_parent = new_mnt->mnt_parent; |
|
root_parent = root_mnt->mnt_parent; |
|
if (IS_MNT_SHARED(old_mnt) || |
|
IS_MNT_SHARED(ex_parent) || |
|
IS_MNT_SHARED(root_parent)) |
|
goto out4; |
|
if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) |
|
goto out4; |
|
if (new_mnt->mnt.mnt_flags & MNT_LOCKED) |
|
goto out4; |
|
error = -ENOENT; |
|
if (d_unlinked(new.dentry)) |
|
goto out4; |
|
error = -EBUSY; |
|
if (new_mnt == root_mnt || old_mnt == root_mnt) |
|
goto out4; /* loop, on the same file system */ |
|
error = -EINVAL; |
|
if (root.mnt->mnt_root != root.dentry) |
|
goto out4; /* not a mountpoint */ |
|
if (!mnt_has_parent(root_mnt)) |
|
goto out4; /* not attached */ |
|
if (new.mnt->mnt_root != new.dentry) |
|
goto out4; /* not a mountpoint */ |
|
if (!mnt_has_parent(new_mnt)) |
|
goto out4; /* not attached */ |
|
/* make sure we can reach put_old from new_root */ |
|
if (!is_path_reachable(old_mnt, old.dentry, &new)) |
|
goto out4; |
|
/* make certain new is below the root */ |
|
if (!is_path_reachable(new_mnt, new.dentry, &root)) |
|
goto out4; |
|
lock_mount_hash(); |
|
umount_mnt(new_mnt); |
|
root_mp = unhash_mnt(root_mnt); /* we'll need its mountpoint */ |
|
if (root_mnt->mnt.mnt_flags & MNT_LOCKED) { |
|
new_mnt->mnt.mnt_flags |= MNT_LOCKED; |
|
root_mnt->mnt.mnt_flags &= ~MNT_LOCKED; |
|
} |
|
/* mount old root on put_old */ |
|
attach_mnt(root_mnt, old_mnt, old_mp); |
|
/* mount new_root on / */ |
|
attach_mnt(new_mnt, root_parent, root_mp); |
|
mnt_add_count(root_parent, -1); |
|
touch_mnt_namespace(current->nsproxy->mnt_ns); |
|
/* A moved mount should not expire automatically */ |
|
list_del_init(&new_mnt->mnt_expire); |
|
put_mountpoint(root_mp); |
|
unlock_mount_hash(); |
|
chroot_fs_refs(&root, &new); |
|
error = 0; |
|
out4: |
|
unlock_mount(old_mp); |
|
if (!error) |
|
mntput_no_expire(ex_parent); |
|
out3: |
|
path_put(&root); |
|
out2: |
|
path_put(&old); |
|
out1: |
|
path_put(&new); |
|
out0: |
|
return error; |
|
} |
|
|
|
static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt) |
|
{ |
|
unsigned int flags = mnt->mnt.mnt_flags; |
|
|
|
/* flags to clear */ |
|
flags &= ~kattr->attr_clr; |
|
/* flags to raise */ |
|
flags |= kattr->attr_set; |
|
|
|
return flags; |
|
} |
|
|
|
static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) |
|
{ |
|
struct vfsmount *m = &mnt->mnt; |
|
struct user_namespace *fs_userns = m->mnt_sb->s_user_ns; |
|
|
|
if (!kattr->mnt_userns) |
|
return 0; |
|
|
|
/* |
|
* Creating an idmapped mount with the filesystem wide idmapping |
|
* doesn't make sense so block that. We don't allow mushy semantics. |
|
*/ |
|
if (kattr->mnt_userns == fs_userns) |
|
return -EINVAL; |
|
|
|
/* |
|
* Once a mount has been idmapped we don't allow it to change its |
|
* mapping. It makes things simpler and callers can just create |
|
* another bind-mount they can idmap if they want to. |
|
*/ |
|
if (is_idmapped_mnt(m)) |
|
return -EPERM; |
|
|
|
/* The underlying filesystem doesn't support idmapped mounts yet. */ |
|
if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP)) |
|
return -EINVAL; |
|
|
|
/* We're not controlling the superblock. */ |
|
if (!ns_capable(fs_userns, CAP_SYS_ADMIN)) |
|
return -EPERM; |
|
|
|
/* Mount has already been visible in the filesystem hierarchy. */ |
|
if (!is_anon_ns(mnt->mnt_ns)) |
|
return -EINVAL; |
|
|
|
return 0; |
|
} |
|
|
|
/** |
|
* mnt_allow_writers() - check whether the attribute change allows writers |
|
* @kattr: the new mount attributes |
|
* @mnt: the mount to which @kattr will be applied |
|
* |
|
* Check whether thew new mount attributes in @kattr allow concurrent writers. |
|
* |
|
* Return: true if writers need to be held, false if not |
|
*/ |
|
static inline bool mnt_allow_writers(const struct mount_kattr *kattr, |
|
const struct mount *mnt) |
|
{ |
|
return (!(kattr->attr_set & MNT_READONLY) || |
|
(mnt->mnt.mnt_flags & MNT_READONLY)) && |
|
!kattr->mnt_userns; |
|
} |
|
|
|
static int mount_setattr_prepare(struct mount_kattr *kattr, struct mount *mnt) |
|
{ |
|
struct mount *m; |
|
int err; |
|
|
|
for (m = mnt; m; m = next_mnt(m, mnt)) { |
|
if (!can_change_locked_flags(m, recalc_flags(kattr, m))) { |
|
err = -EPERM; |
|
break; |
|
} |
|
|
|
err = can_idmap_mount(kattr, m); |
|
if (err) |
|
break; |
|
|
|
if (!mnt_allow_writers(kattr, m)) { |
|
err = mnt_hold_writers(m); |
|
if (err) |
|
break; |
|
} |
|
|
|
if (!kattr->recurse) |
|
return 0; |
|
} |
|
|
|
if (err) { |
|
struct mount *p; |
|
|
|
/* |
|
* If we had to call mnt_hold_writers() MNT_WRITE_HOLD will |
|
* be set in @mnt_flags. The loop unsets MNT_WRITE_HOLD for all |
|
* mounts and needs to take care to include the first mount. |
|
*/ |
|
for (p = mnt; p; p = next_mnt(p, mnt)) { |
|
/* If we had to hold writers unblock them. */ |
|
if (p->mnt.mnt_flags & MNT_WRITE_HOLD) |
|
mnt_unhold_writers(p); |
|
|
|
/* |
|
* We're done once the first mount we changed got |
|
* MNT_WRITE_HOLD unset. |
|
*/ |
|
if (p == m) |
|
break; |
|
} |
|
} |
|
return err; |
|
} |
|
|
|
static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) |
|
{ |
|
struct user_namespace *mnt_userns, *old_mnt_userns; |
|
|
|
if (!kattr->mnt_userns) |
|
return; |
|
|
|
/* |
|
* We're the only ones able to change the mount's idmapping. So |
|
* mnt->mnt.mnt_userns is stable and we can retrieve it directly. |
|
*/ |
|
old_mnt_userns = mnt->mnt.mnt_userns; |
|
|
|
mnt_userns = get_user_ns(kattr->mnt_userns); |
|
/* Pairs with smp_load_acquire() in mnt_user_ns(). */ |
|
smp_store_release(&mnt->mnt.mnt_userns, mnt_userns); |
|
|
|
/* |
|
* If this is an idmapped filesystem drop the reference we've taken |
|
* in vfs_create_mount() before. |
|
*/ |
|
if (!initial_idmapping(old_mnt_userns)) |
|
put_user_ns(old_mnt_userns); |
|
} |
|
|
|
static void mount_setattr_commit(struct mount_kattr *kattr, struct mount *mnt) |
|
{ |
|
struct mount *m; |
|
|
|
for (m = mnt; m; m = next_mnt(m, mnt)) { |
|
unsigned int flags; |
|
|
|
do_idmap_mount(kattr, m); |
|
flags = recalc_flags(kattr, m); |
|
WRITE_ONCE(m->mnt.mnt_flags, flags); |
|
|
|
/* If we had to hold writers unblock them. */ |
|
if (m->mnt.mnt_flags & MNT_WRITE_HOLD) |
|
mnt_unhold_writers(m); |
|
|
|
if (kattr->propagation) |
|
change_mnt_propagation(m, kattr->propagation); |
|
if (!kattr->recurse) |
|
break; |
|
} |
|
touch_mnt_namespace(mnt->mnt_ns); |
|
} |
|
|
|
static int do_mount_setattr(struct path *path, struct mount_kattr *kattr) |
|
{ |
|
struct mount *mnt = real_mount(path->mnt); |
|
int err = 0; |
|
|
|
if (path->dentry != mnt->mnt.mnt_root) |
|
return -EINVAL; |
|
|
|
if (kattr->propagation) { |
|
/* |
|
* Only take namespace_lock() if we're actually changing |
|
* propagation. |
|
*/ |
|
namespace_lock(); |
|
if (kattr->propagation == MS_SHARED) { |
|
err = invent_group_ids(mnt, kattr->recurse); |
|
if (err) { |
|
namespace_unlock(); |
|
return err; |
|
} |
|
} |
|
} |
|
|
|
err = -EINVAL; |
|
lock_mount_hash(); |
|
|
|
/* Ensure that this isn't anything purely vfs internal. */ |
|
if (!is_mounted(&mnt->mnt)) |
|
goto out; |
|
|
|
/* |
|
* If this is an attached mount make sure it's located in the callers |
|
* mount namespace. If it's not don't let the caller interact with it. |
|
* If this is a detached mount make sure it has an anonymous mount |
|
* namespace attached to it, i.e. we've created it via OPEN_TREE_CLONE. |
|
*/ |
|
if (!(mnt_has_parent(mnt) ? check_mnt(mnt) : is_anon_ns(mnt->mnt_ns))) |
|
goto out; |
|
|
|
/* |
|
* First, we get the mount tree in a shape where we can change mount |
|
* properties without failure. If we succeeded to do so we commit all |
|
* changes and if we failed we clean up. |
|
*/ |
|
err = mount_setattr_prepare(kattr, mnt); |
|
if (!err) |
|
mount_setattr_commit(kattr, mnt); |
|
|
|
out: |
|
unlock_mount_hash(); |
|
|
|
if (kattr->propagation) { |
|
namespace_unlock(); |
|
if (err) |
|
cleanup_group_ids(mnt, NULL); |
|
} |
|
|
|
return err; |
|
} |
|
|
|
static int build_mount_idmapped(const struct mount_attr *attr, size_t usize, |
|
struct mount_kattr *kattr, unsigned int flags) |
|
{ |
|
int err = 0; |
|
struct ns_common *ns; |
|
struct user_namespace *mnt_userns; |
|
struct file *file; |
|
|
|
if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP)) |
|
return 0; |
|
|
|
/* |
|
* We currently do not support clearing an idmapped mount. If this ever |
|
* is a use-case we can revisit this but for now let's keep it simple |
|
* and not allow it. |
|
*/ |
|
if (attr->attr_clr & MOUNT_ATTR_IDMAP) |
|
return -EINVAL; |
|
|
|
if (attr->userns_fd > INT_MAX) |
|
return -EINVAL; |
|
|
|
file = fget(attr->userns_fd); |
|
if (!file) |
|
return -EBADF; |
|
|
|
if (!proc_ns_file(file)) { |
|
err = -EINVAL; |
|
goto out_fput; |
|
} |
|
|
|
ns = get_proc_ns(file_inode(file)); |
|
if (ns->ops->type != CLONE_NEWUSER) { |
|
err = -EINVAL; |
|
goto out_fput; |
|
} |
|
|
|
/* |
|
* The initial idmapping cannot be used to create an idmapped |
|
* mount. We use the initial idmapping as an indicator of a mount |
|
* that is not idmapped. It can simply be passed into helpers that |
|
* are aware of idmapped mounts as a convenient shortcut. A user |
|
* can just create a dedicated identity mapping to achieve the same |
|
* result. |
|
*/ |
|
mnt_userns = container_of(ns, struct user_namespace, ns); |
|
if (initial_idmapping(mnt_userns)) { |
|
err = -EPERM; |
|
goto out_fput; |
|
} |
|
|
|
/* We're not controlling the target namespace. */ |
|
if (!ns_capable(mnt_userns, CAP_SYS_ADMIN)) { |
|
err = -EPERM; |
|
goto out_fput; |
|
} |
|
|
|
kattr->mnt_userns = get_user_ns(mnt_userns); |
|
|
|
out_fput: |
|
fput(file); |
|
return err; |
|
} |
|
|
|
static int build_mount_kattr(const struct mount_attr *attr, size_t usize, |
|
struct mount_kattr *kattr, unsigned int flags) |
|
{ |
|
unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW; |
|
|
|
if (flags & AT_NO_AUTOMOUNT) |
|
lookup_flags &= ~LOOKUP_AUTOMOUNT; |
|
if (flags & AT_SYMLINK_NOFOLLOW) |
|
lookup_flags &= ~LOOKUP_FOLLOW; |
|
if (flags & AT_EMPTY_PATH) |
|
lookup_flags |= LOOKUP_EMPTY; |
|
|
|
*kattr = (struct mount_kattr) { |
|
.lookup_flags = lookup_flags, |
|
.recurse = !!(flags & AT_RECURSIVE), |
|
}; |
|
|
|
if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS) |
|
return -EINVAL; |
|
if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1) |
|
return -EINVAL; |
|
kattr->propagation = attr->propagation; |
|
|
|
if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS) |
|
return -EINVAL; |
|
|
|
kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set); |
|
kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr); |
|
|
|
/* |
|
* Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap, |
|
* users wanting to transition to a different atime setting cannot |
|
* simply specify the atime setting in @attr_set, but must also |
|
* specify MOUNT_ATTR__ATIME in the @attr_clr field. |
|
* So ensure that MOUNT_ATTR__ATIME can't be partially set in |
|
* @attr_clr and that @attr_set can't have any atime bits set if |
|
* MOUNT_ATTR__ATIME isn't set in @attr_clr. |
|
*/ |
|
if (attr->attr_clr & MOUNT_ATTR__ATIME) { |
|
if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME) |
|
return -EINVAL; |
|
|
|
/* |
|
* Clear all previous time settings as they are mutually |
|
* exclusive. |
|
*/ |
|
kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME; |
|
switch (attr->attr_set & MOUNT_ATTR__ATIME) { |
|
case MOUNT_ATTR_RELATIME: |
|
kattr->attr_set |= MNT_RELATIME; |
|
break; |
|
case MOUNT_ATTR_NOATIME: |
|
kattr->attr_set |= MNT_NOATIME; |
|
break; |
|
case MOUNT_ATTR_STRICTATIME: |
|
break; |
|
default: |
|
return -EINVAL; |
|
} |
|
} else { |
|
if (attr->attr_set & MOUNT_ATTR__ATIME) |
|
return -EINVAL; |
|
} |
|
|
|
return build_mount_idmapped(attr, usize, kattr, flags); |
|
} |
|
|
|
static void finish_mount_kattr(struct mount_kattr *kattr) |
|
{ |
|
put_user_ns(kattr->mnt_userns); |
|
kattr->mnt_userns = NULL; |
|
} |
|
|
|
SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path, |
|
unsigned int, flags, struct mount_attr __user *, uattr, |
|
size_t, usize) |
|
{ |
|
int err; |
|
struct path target; |
|
struct mount_attr attr; |
|
struct mount_kattr kattr; |
|
|
|
BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0); |
|
|
|
if (flags & ~(AT_EMPTY_PATH | |
|
AT_RECURSIVE | |
|
AT_SYMLINK_NOFOLLOW | |
|
AT_NO_AUTOMOUNT)) |
|
return -EINVAL; |
|
|
|
if (unlikely(usize > PAGE_SIZE)) |
|
return -E2BIG; |
|
if (unlikely(usize < MOUNT_ATTR_SIZE_VER0)) |
|
return -EINVAL; |
|
|
|
if (!may_mount()) |
|
return -EPERM; |
|
|
|
err = copy_struct_from_user(&attr, sizeof(attr), uattr, usize); |
|
if (err) |
|
return err; |
|
|
|
/* Don't bother walking through the mounts if this is a nop. */ |
|
if (attr.attr_set == 0 && |
|
attr.attr_clr == 0 && |
|
attr.propagation == 0) |
|
return 0; |
|
|
|
err = build_mount_kattr(&attr, usize, &kattr, flags); |
|
if (err) |
|
return err; |
|
|
|
err = user_path_at(dfd, path, kattr.lookup_flags, &target); |
|
if (!err) { |
|
err = do_mount_setattr(&target, &kattr); |
|
path_put(&target); |
|
} |
|
finish_mount_kattr(&kattr); |
|
return err; |
|
} |
|
|
|
static void __init init_mount_tree(void) |
|
{ |
|
struct vfsmount *mnt; |
|
struct mount *m; |
|
struct mnt_namespace *ns; |
|
struct path root; |
|
|
|
mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL); |
|
if (IS_ERR(mnt)) |
|
panic("Can't create rootfs"); |
|
|
|
ns = alloc_mnt_ns(&init_user_ns, false); |
|
if (IS_ERR(ns)) |
|
panic("Can't allocate initial namespace"); |
|
m = real_mount(mnt); |
|
m->mnt_ns = ns; |
|
ns->root = m; |
|
ns->mounts = 1; |
|
list_add(&m->mnt_list, &ns->list); |
|
init_task.nsproxy->mnt_ns = ns; |
|
get_mnt_ns(ns); |
|
|
|
root.mnt = mnt; |
|
root.dentry = mnt->mnt_root; |
|
mnt->mnt_flags |= MNT_LOCKED; |
|
|
|
set_fs_pwd(current->fs, &root); |
|
set_fs_root(current->fs, &root); |
|
} |
|
|
|
void __init mnt_init(void) |
|
{ |
|
int err; |
|
|
|
mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), |
|
0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); |
|
|
|
mount_hashtable = alloc_large_system_hash("Mount-cache", |
|
sizeof(struct hlist_head), |
|
mhash_entries, 19, |
|
HASH_ZERO, |
|
&m_hash_shift, &m_hash_mask, 0, 0); |
|
mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache", |
|
sizeof(struct hlist_head), |
|
mphash_entries, 19, |
|
HASH_ZERO, |
|
&mp_hash_shift, &mp_hash_mask, 0, 0); |
|
|
|
if (!mount_hashtable || !mountpoint_hashtable) |
|
panic("Failed to allocate mount hash table\n"); |
|
|
|
kernfs_init(); |
|
|
|
err = sysfs_init(); |
|
if (err) |
|
printk(KERN_WARNING "%s: sysfs_init error: %d\n", |
|
__func__, err); |
|
fs_kobj = kobject_create_and_add("fs", NULL); |
|
if (!fs_kobj) |
|
printk(KERN_WARNING "%s: kobj create error\n", __func__); |
|
shmem_init(); |
|
init_rootfs(); |
|
init_mount_tree(); |
|
} |
|
|
|
void put_mnt_ns(struct mnt_namespace *ns) |
|
{ |
|
if (!refcount_dec_and_test(&ns->ns.count)) |
|
return; |
|
drop_collected_mounts(&ns->root->mnt); |
|
free_mnt_ns(ns); |
|
} |
|
|
|
struct vfsmount *kern_mount(struct file_system_type *type) |
|
{ |
|
struct vfsmount *mnt; |
|
mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL); |
|
if (!IS_ERR(mnt)) { |
|
/* |
|
* it is a longterm mount, don't release mnt until |
|
* we unmount before file sys is unregistered |
|
*/ |
|
real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; |
|
} |
|
return mnt; |
|
} |
|
EXPORT_SYMBOL_GPL(kern_mount); |
|
|
|
void kern_unmount(struct vfsmount *mnt) |
|
{ |
|
/* release long term mount so mount point can be released */ |
|
if (!IS_ERR_OR_NULL(mnt)) { |
|
real_mount(mnt)->mnt_ns = NULL; |
|
synchronize_rcu(); /* yecchhh... */ |
|
mntput(mnt); |
|
} |
|
} |
|
EXPORT_SYMBOL(kern_unmount); |
|
|
|
void kern_unmount_array(struct vfsmount *mnt[], unsigned int num) |
|
{ |
|
unsigned int i; |
|
|
|
for (i = 0; i < num; i++) |
|
if (mnt[i]) |
|
real_mount(mnt[i])->mnt_ns = NULL; |
|
synchronize_rcu_expedited(); |
|
for (i = 0; i < num; i++) |
|
mntput(mnt[i]); |
|
} |
|
EXPORT_SYMBOL(kern_unmount_array); |
|
|
|
bool our_mnt(struct vfsmount *mnt) |
|
{ |
|
return check_mnt(real_mount(mnt)); |
|
} |
|
|
|
bool current_chrooted(void) |
|
{ |
|
/* Does the current process have a non-standard root */ |
|
struct path ns_root; |
|
struct path fs_root; |
|
bool chrooted; |
|
|
|
/* Find the namespace root */ |
|
ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; |
|
ns_root.dentry = ns_root.mnt->mnt_root; |
|
path_get(&ns_root); |
|
while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root)) |
|
; |
|
|
|
get_fs_root(current->fs, &fs_root); |
|
|
|
chrooted = !path_equal(&fs_root, &ns_root); |
|
|
|
path_put(&fs_root); |
|
path_put(&ns_root); |
|
|
|
return chrooted; |
|
} |
|
|
|
static bool mnt_already_visible(struct mnt_namespace *ns, |
|
const struct super_block *sb, |
|
int *new_mnt_flags) |
|
{ |
|
int new_flags = *new_mnt_flags; |
|
struct mount *mnt; |
|
bool visible = false; |
|
|
|
down_read(&namespace_sem); |
|
lock_ns_list(ns); |
|
list_for_each_entry(mnt, &ns->list, mnt_list) { |
|
struct mount *child; |
|
int mnt_flags; |
|
|
|
if (mnt_is_cursor(mnt)) |
|
continue; |
|
|
|
if (mnt->mnt.mnt_sb->s_type != sb->s_type) |
|
continue; |
|
|
|
/* This mount is not fully visible if it's root directory |
|
* is not the root directory of the filesystem. |
|
*/ |
|
if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root) |
|
continue; |
|
|
|
/* A local view of the mount flags */ |
|
mnt_flags = mnt->mnt.mnt_flags; |
|
|
|
/* Don't miss readonly hidden in the superblock flags */ |
|
if (sb_rdonly(mnt->mnt.mnt_sb)) |
|
mnt_flags |= MNT_LOCK_READONLY; |
|
|
|
/* Verify the mount flags are equal to or more permissive |
|
* than the proposed new mount. |
|
*/ |
|
if ((mnt_flags & MNT_LOCK_READONLY) && |
|
!(new_flags & MNT_READONLY)) |
|
continue; |
|
if ((mnt_flags & MNT_LOCK_ATIME) && |
|
((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) |
|
continue; |
|
|
|
/* This mount is not fully visible if there are any |
|
* locked child mounts that cover anything except for |
|
* empty directories. |
|
*/ |
|
list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { |
|
struct inode *inode = child->mnt_mountpoint->d_inode; |
|
/* Only worry about locked mounts */ |
|
if (!(child->mnt.mnt_flags & MNT_LOCKED)) |
|
continue; |
|
/* Is the directory permanetly empty? */ |
|
if (!is_empty_dir_inode(inode)) |
|
goto next; |
|
} |
|
/* Preserve the locked attributes */ |
|
*new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \ |
|
MNT_LOCK_ATIME); |
|
visible = true; |
|
goto found; |
|
next: ; |
|
} |
|
found: |
|
unlock_ns_list(ns); |
|
up_read(&namespace_sem); |
|
return visible; |
|
} |
|
|
|
static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags) |
|
{ |
|
const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV; |
|
struct mnt_namespace *ns = current->nsproxy->mnt_ns; |
|
unsigned long s_iflags; |
|
|
|
if (ns->user_ns == &init_user_ns) |
|
return false; |
|
|
|
/* Can this filesystem be too revealing? */ |
|
s_iflags = sb->s_iflags; |
|
if (!(s_iflags & SB_I_USERNS_VISIBLE)) |
|
return false; |
|
|
|
if ((s_iflags & required_iflags) != required_iflags) { |
|
WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n", |
|
required_iflags); |
|
return true; |
|
} |
|
|
|
return !mnt_already_visible(ns, sb, new_mnt_flags); |
|
} |
|
|
|
bool mnt_may_suid(struct vfsmount *mnt) |
|
{ |
|
/* |
|
* Foreign mounts (accessed via fchdir or through /proc |
|
* symlinks) are always treated as if they are nosuid. This |
|
* prevents namespaces from trusting potentially unsafe |
|
* suid/sgid bits, file caps, or security labels that originate |
|
* in other namespaces. |
|
*/ |
|
return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) && |
|
current_in_userns(mnt->mnt_sb->s_user_ns); |
|
} |
|
|
|
static struct ns_common *mntns_get(struct task_struct *task) |
|
{ |
|
struct ns_common *ns = NULL; |
|
struct nsproxy *nsproxy; |
|
|
|
task_lock(task); |
|
nsproxy = task->nsproxy; |
|
if (nsproxy) { |
|
ns = &nsproxy->mnt_ns->ns; |
|
get_mnt_ns(to_mnt_ns(ns)); |
|
} |
|
task_unlock(task); |
|
|
|
return ns; |
|
} |
|
|
|
static void mntns_put(struct ns_common *ns) |
|
{ |
|
put_mnt_ns(to_mnt_ns(ns)); |
|
} |
|
|
|
static int mntns_install(struct nsset *nsset, struct ns_common *ns) |
|
{ |
|
struct nsproxy *nsproxy = nsset->nsproxy; |
|
struct fs_struct *fs = nsset->fs; |
|
struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns; |
|
struct user_namespace *user_ns = nsset->cred->user_ns; |
|
struct path root; |
|
int err; |
|
|
|
if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || |
|
!ns_capable(user_ns, CAP_SYS_CHROOT) || |
|
!ns_capable(user_ns, CAP_SYS_ADMIN)) |
|
return -EPERM; |
|
|
|
if (is_anon_ns(mnt_ns)) |
|
return -EINVAL; |
|
|
|
if (fs->users != 1) |
|
return -EINVAL; |
|
|
|
get_mnt_ns(mnt_ns); |
|
old_mnt_ns = nsproxy->mnt_ns; |
|
nsproxy->mnt_ns = mnt_ns; |
|
|
|
/* Find the root */ |
|
err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt, |
|
"/", LOOKUP_DOWN, &root); |
|
if (err) { |
|
/* revert to old namespace */ |
|
nsproxy->mnt_ns = old_mnt_ns; |
|
put_mnt_ns(mnt_ns); |
|
return err; |
|
} |
|
|
|
put_mnt_ns(old_mnt_ns); |
|
|
|
/* Update the pwd and root */ |
|
set_fs_pwd(fs, &root); |
|
set_fs_root(fs, &root); |
|
|
|
path_put(&root); |
|
return 0; |
|
} |
|
|
|
static struct user_namespace *mntns_owner(struct ns_common *ns) |
|
{ |
|
return to_mnt_ns(ns)->user_ns; |
|
} |
|
|
|
const struct proc_ns_operations mntns_operations = { |
|
.name = "mnt", |
|
.type = CLONE_NEWNS, |
|
.get = mntns_get, |
|
.put = mntns_put, |
|
.install = mntns_install, |
|
.owner = mntns_owner, |
|
}; |
|
|
|
#ifdef CONFIG_SYSCTL |
|
static struct ctl_table fs_namespace_sysctls[] = { |
|
{ |
|
.procname = "mount-max", |
|
.data = &sysctl_mount_max, |
|
.maxlen = sizeof(unsigned int), |
|
.mode = 0644, |
|
.proc_handler = proc_dointvec_minmax, |
|
.extra1 = SYSCTL_ONE, |
|
}, |
|
{ } |
|
}; |
|
|
|
static int __init init_fs_namespace_sysctls(void) |
|
{ |
|
register_sysctl_init("fs", fs_namespace_sysctls); |
|
return 0; |
|
} |
|
fs_initcall(init_fs_namespace_sysctls); |
|
|
|
#endif /* CONFIG_SYSCTL */
|
|
|