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479 lines
10 KiB
479 lines
10 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* devtmpfs - kernel-maintained tmpfs-based /dev |
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* |
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* Copyright (C) 2009, Kay Sievers <[email protected]> |
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* |
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* During bootup, before any driver core device is registered, |
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* devtmpfs, a tmpfs-based filesystem is created. Every driver-core |
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* device which requests a device node, will add a node in this |
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* filesystem. |
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* By default, all devices are named after the name of the device, |
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* owned by root and have a default mode of 0600. Subsystems can |
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* overwrite the default setting if needed. |
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*/ |
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#include <linux/kernel.h> |
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#include <linux/syscalls.h> |
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#include <linux/mount.h> |
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#include <linux/device.h> |
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#include <linux/genhd.h> |
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#include <linux/namei.h> |
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#include <linux/fs.h> |
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#include <linux/shmem_fs.h> |
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#include <linux/ramfs.h> |
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#include <linux/sched.h> |
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#include <linux/slab.h> |
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#include <linux/kthread.h> |
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#include <linux/init_syscalls.h> |
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#include <uapi/linux/mount.h> |
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#include "base.h" |
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static struct task_struct *thread; |
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static int __initdata mount_dev = IS_ENABLED(CONFIG_DEVTMPFS_MOUNT); |
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static DEFINE_SPINLOCK(req_lock); |
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static struct req { |
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struct req *next; |
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struct completion done; |
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int err; |
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const char *name; |
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umode_t mode; /* 0 => delete */ |
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kuid_t uid; |
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kgid_t gid; |
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struct device *dev; |
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} *requests; |
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static int __init mount_param(char *str) |
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{ |
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mount_dev = simple_strtoul(str, NULL, 0); |
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return 1; |
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} |
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__setup("devtmpfs.mount=", mount_param); |
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static struct vfsmount *mnt; |
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static struct dentry *public_dev_mount(struct file_system_type *fs_type, int flags, |
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const char *dev_name, void *data) |
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{ |
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struct super_block *s = mnt->mnt_sb; |
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atomic_inc(&s->s_active); |
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down_write(&s->s_umount); |
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return dget(s->s_root); |
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} |
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static struct file_system_type internal_fs_type = { |
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.name = "devtmpfs", |
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#ifdef CONFIG_TMPFS |
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.init_fs_context = shmem_init_fs_context, |
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.parameters = shmem_fs_parameters, |
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#else |
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.init_fs_context = ramfs_init_fs_context, |
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.parameters = ramfs_fs_parameters, |
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#endif |
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.kill_sb = kill_litter_super, |
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}; |
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static struct file_system_type dev_fs_type = { |
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.name = "devtmpfs", |
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.mount = public_dev_mount, |
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}; |
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#ifdef CONFIG_BLOCK |
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static inline int is_blockdev(struct device *dev) |
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{ |
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return dev->class == &block_class; |
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} |
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#else |
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static inline int is_blockdev(struct device *dev) { return 0; } |
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#endif |
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static int devtmpfs_submit_req(struct req *req, const char *tmp) |
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{ |
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init_completion(&req->done); |
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spin_lock(&req_lock); |
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req->next = requests; |
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requests = req; |
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spin_unlock(&req_lock); |
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wake_up_process(thread); |
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wait_for_completion(&req->done); |
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kfree(tmp); |
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return req->err; |
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} |
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int devtmpfs_create_node(struct device *dev) |
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{ |
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const char *tmp = NULL; |
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struct req req; |
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if (!thread) |
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return 0; |
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req.mode = 0; |
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req.uid = GLOBAL_ROOT_UID; |
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req.gid = GLOBAL_ROOT_GID; |
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req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp); |
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if (!req.name) |
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return -ENOMEM; |
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if (req.mode == 0) |
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req.mode = 0600; |
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if (is_blockdev(dev)) |
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req.mode |= S_IFBLK; |
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else |
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req.mode |= S_IFCHR; |
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req.dev = dev; |
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return devtmpfs_submit_req(&req, tmp); |
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} |
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int devtmpfs_delete_node(struct device *dev) |
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{ |
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const char *tmp = NULL; |
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struct req req; |
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if (!thread) |
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return 0; |
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req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp); |
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if (!req.name) |
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return -ENOMEM; |
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req.mode = 0; |
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req.dev = dev; |
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return devtmpfs_submit_req(&req, tmp); |
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} |
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static int dev_mkdir(const char *name, umode_t mode) |
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{ |
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struct dentry *dentry; |
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struct path path; |
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int err; |
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dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY); |
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if (IS_ERR(dentry)) |
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return PTR_ERR(dentry); |
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err = vfs_mkdir(&init_user_ns, d_inode(path.dentry), dentry, mode); |
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if (!err) |
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/* mark as kernel-created inode */ |
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d_inode(dentry)->i_private = &thread; |
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done_path_create(&path, dentry); |
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return err; |
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} |
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static int create_path(const char *nodepath) |
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{ |
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char *path; |
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char *s; |
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int err = 0; |
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/* parent directories do not exist, create them */ |
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path = kstrdup(nodepath, GFP_KERNEL); |
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if (!path) |
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return -ENOMEM; |
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s = path; |
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for (;;) { |
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s = strchr(s, '/'); |
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if (!s) |
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break; |
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s[0] = '\0'; |
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err = dev_mkdir(path, 0755); |
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if (err && err != -EEXIST) |
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break; |
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s[0] = '/'; |
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s++; |
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} |
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kfree(path); |
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return err; |
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} |
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static int handle_create(const char *nodename, umode_t mode, kuid_t uid, |
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kgid_t gid, struct device *dev) |
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{ |
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struct dentry *dentry; |
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struct path path; |
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int err; |
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dentry = kern_path_create(AT_FDCWD, nodename, &path, 0); |
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if (dentry == ERR_PTR(-ENOENT)) { |
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create_path(nodename); |
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dentry = kern_path_create(AT_FDCWD, nodename, &path, 0); |
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} |
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if (IS_ERR(dentry)) |
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return PTR_ERR(dentry); |
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err = vfs_mknod(&init_user_ns, d_inode(path.dentry), dentry, mode, |
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dev->devt); |
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if (!err) { |
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struct iattr newattrs; |
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newattrs.ia_mode = mode; |
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newattrs.ia_uid = uid; |
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newattrs.ia_gid = gid; |
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newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID; |
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inode_lock(d_inode(dentry)); |
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notify_change(&init_user_ns, dentry, &newattrs, NULL); |
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inode_unlock(d_inode(dentry)); |
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/* mark as kernel-created inode */ |
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d_inode(dentry)->i_private = &thread; |
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} |
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done_path_create(&path, dentry); |
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return err; |
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} |
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static int dev_rmdir(const char *name) |
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{ |
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struct path parent; |
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struct dentry *dentry; |
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int err; |
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dentry = kern_path_locked(name, &parent); |
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if (IS_ERR(dentry)) |
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return PTR_ERR(dentry); |
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if (d_really_is_positive(dentry)) { |
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if (d_inode(dentry)->i_private == &thread) |
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err = vfs_rmdir(&init_user_ns, d_inode(parent.dentry), |
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dentry); |
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else |
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err = -EPERM; |
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} else { |
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err = -ENOENT; |
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} |
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dput(dentry); |
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inode_unlock(d_inode(parent.dentry)); |
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path_put(&parent); |
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return err; |
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} |
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static int delete_path(const char *nodepath) |
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{ |
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char *path; |
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int err = 0; |
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path = kstrdup(nodepath, GFP_KERNEL); |
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if (!path) |
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return -ENOMEM; |
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for (;;) { |
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char *base; |
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base = strrchr(path, '/'); |
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if (!base) |
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break; |
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base[0] = '\0'; |
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err = dev_rmdir(path); |
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if (err) |
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break; |
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} |
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kfree(path); |
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return err; |
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} |
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static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat) |
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{ |
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/* did we create it */ |
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if (inode->i_private != &thread) |
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return 0; |
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/* does the dev_t match */ |
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if (is_blockdev(dev)) { |
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if (!S_ISBLK(stat->mode)) |
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return 0; |
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} else { |
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if (!S_ISCHR(stat->mode)) |
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return 0; |
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} |
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if (stat->rdev != dev->devt) |
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return 0; |
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/* ours */ |
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return 1; |
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} |
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static int handle_remove(const char *nodename, struct device *dev) |
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{ |
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struct path parent; |
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struct dentry *dentry; |
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int deleted = 0; |
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int err; |
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dentry = kern_path_locked(nodename, &parent); |
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if (IS_ERR(dentry)) |
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return PTR_ERR(dentry); |
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if (d_really_is_positive(dentry)) { |
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struct kstat stat; |
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struct path p = {.mnt = parent.mnt, .dentry = dentry}; |
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err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE, |
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AT_STATX_SYNC_AS_STAT); |
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if (!err && dev_mynode(dev, d_inode(dentry), &stat)) { |
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struct iattr newattrs; |
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/* |
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* before unlinking this node, reset permissions |
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* of possible references like hardlinks |
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*/ |
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newattrs.ia_uid = GLOBAL_ROOT_UID; |
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newattrs.ia_gid = GLOBAL_ROOT_GID; |
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newattrs.ia_mode = stat.mode & ~0777; |
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newattrs.ia_valid = |
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ATTR_UID|ATTR_GID|ATTR_MODE; |
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inode_lock(d_inode(dentry)); |
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notify_change(&init_user_ns, dentry, &newattrs, NULL); |
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inode_unlock(d_inode(dentry)); |
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err = vfs_unlink(&init_user_ns, d_inode(parent.dentry), |
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dentry, NULL); |
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if (!err || err == -ENOENT) |
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deleted = 1; |
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} |
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} else { |
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err = -ENOENT; |
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} |
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dput(dentry); |
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inode_unlock(d_inode(parent.dentry)); |
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path_put(&parent); |
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if (deleted && strchr(nodename, '/')) |
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delete_path(nodename); |
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return err; |
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} |
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/* |
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* If configured, or requested by the commandline, devtmpfs will be |
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* auto-mounted after the kernel mounted the root filesystem. |
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*/ |
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int __init devtmpfs_mount(void) |
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{ |
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int err; |
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if (!mount_dev) |
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return 0; |
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if (!thread) |
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return 0; |
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err = init_mount("devtmpfs", "dev", "devtmpfs", MS_SILENT, NULL); |
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if (err) |
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printk(KERN_INFO "devtmpfs: error mounting %i\n", err); |
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else |
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printk(KERN_INFO "devtmpfs: mounted\n"); |
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return err; |
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} |
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static __initdata DECLARE_COMPLETION(setup_done); |
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static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid, |
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struct device *dev) |
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{ |
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if (mode) |
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return handle_create(name, mode, uid, gid, dev); |
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else |
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return handle_remove(name, dev); |
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} |
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static void __noreturn devtmpfs_work_loop(void) |
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{ |
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while (1) { |
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spin_lock(&req_lock); |
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while (requests) { |
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struct req *req = requests; |
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requests = NULL; |
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spin_unlock(&req_lock); |
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while (req) { |
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struct req *next = req->next; |
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req->err = handle(req->name, req->mode, |
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req->uid, req->gid, req->dev); |
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complete(&req->done); |
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req = next; |
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} |
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spin_lock(&req_lock); |
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} |
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__set_current_state(TASK_INTERRUPTIBLE); |
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spin_unlock(&req_lock); |
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schedule(); |
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} |
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} |
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static noinline int __init devtmpfs_setup(void *p) |
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{ |
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int err; |
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err = ksys_unshare(CLONE_NEWNS); |
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if (err) |
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goto out; |
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err = init_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, NULL); |
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if (err) |
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goto out; |
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init_chdir("/.."); /* will traverse into overmounted root */ |
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init_chroot("."); |
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out: |
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*(int *)p = err; |
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return err; |
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} |
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/* |
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* The __ref is because devtmpfs_setup needs to be __init for the routines it |
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* calls. That call is done while devtmpfs_init, which is marked __init, |
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* synchronously waits for it to complete. |
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*/ |
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static int __ref devtmpfsd(void *p) |
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{ |
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int err = devtmpfs_setup(p); |
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complete(&setup_done); |
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if (err) |
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return err; |
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devtmpfs_work_loop(); |
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return 0; |
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} |
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/* |
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* Create devtmpfs instance, driver-core devices will add their device |
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* nodes here. |
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*/ |
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int __init devtmpfs_init(void) |
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{ |
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char opts[] = "mode=0755"; |
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int err; |
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mnt = vfs_kern_mount(&internal_fs_type, 0, "devtmpfs", opts); |
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if (IS_ERR(mnt)) { |
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printk(KERN_ERR "devtmpfs: unable to create devtmpfs %ld\n", |
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PTR_ERR(mnt)); |
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return PTR_ERR(mnt); |
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} |
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err = register_filesystem(&dev_fs_type); |
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if (err) { |
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printk(KERN_ERR "devtmpfs: unable to register devtmpfs " |
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"type %i\n", err); |
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return err; |
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} |
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thread = kthread_run(devtmpfsd, &err, "kdevtmpfs"); |
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if (!IS_ERR(thread)) { |
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wait_for_completion(&setup_done); |
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} else { |
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err = PTR_ERR(thread); |
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thread = NULL; |
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} |
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if (err) { |
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printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err); |
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unregister_filesystem(&dev_fs_type); |
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return err; |
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} |
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printk(KERN_INFO "devtmpfs: initialized\n"); |
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return 0; |
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}
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