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251 lines
5.9 KiB
251 lines
5.9 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* The "user cache". |
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* |
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* (C) Copyright 1991-2000 Linus Torvalds |
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* |
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* We have a per-user structure to keep track of how many |
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* processes, files etc the user has claimed, in order to be |
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* able to have per-user limits for system resources. |
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*/ |
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#include <linux/init.h> |
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#include <linux/sched.h> |
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#include <linux/slab.h> |
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#include <linux/bitops.h> |
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#include <linux/key.h> |
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#include <linux/sched/user.h> |
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#include <linux/interrupt.h> |
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#include <linux/export.h> |
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#include <linux/user_namespace.h> |
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#include <linux/proc_ns.h> |
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/* |
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* userns count is 1 for root user, 1 for init_uts_ns, |
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* and 1 for... ? |
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*/ |
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struct user_namespace init_user_ns = { |
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.uid_map = { |
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.nr_extents = 1, |
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{ |
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.extent[0] = { |
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.first = 0, |
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.lower_first = 0, |
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.count = 4294967295U, |
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}, |
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}, |
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}, |
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.gid_map = { |
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.nr_extents = 1, |
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{ |
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.extent[0] = { |
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.first = 0, |
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.lower_first = 0, |
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.count = 4294967295U, |
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}, |
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}, |
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}, |
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.projid_map = { |
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.nr_extents = 1, |
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{ |
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.extent[0] = { |
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.first = 0, |
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.lower_first = 0, |
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.count = 4294967295U, |
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}, |
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}, |
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}, |
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.ns.count = REFCOUNT_INIT(3), |
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.owner = GLOBAL_ROOT_UID, |
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.group = GLOBAL_ROOT_GID, |
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.ns.inum = PROC_USER_INIT_INO, |
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#ifdef CONFIG_USER_NS |
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.ns.ops = &userns_operations, |
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#endif |
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.flags = USERNS_INIT_FLAGS, |
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#ifdef CONFIG_KEYS |
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.keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list), |
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.keyring_sem = __RWSEM_INITIALIZER(init_user_ns.keyring_sem), |
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#endif |
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}; |
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EXPORT_SYMBOL_GPL(init_user_ns); |
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/* |
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* UID task count cache, to get fast user lookup in "alloc_uid" |
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* when changing user ID's (ie setuid() and friends). |
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*/ |
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#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7) |
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#define UIDHASH_SZ (1 << UIDHASH_BITS) |
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#define UIDHASH_MASK (UIDHASH_SZ - 1) |
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#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK) |
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#define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid)))) |
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static struct kmem_cache *uid_cachep; |
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static struct hlist_head uidhash_table[UIDHASH_SZ]; |
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/* |
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* The uidhash_lock is mostly taken from process context, but it is |
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* occasionally also taken from softirq/tasklet context, when |
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* task-structs get RCU-freed. Hence all locking must be softirq-safe. |
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* But free_uid() is also called with local interrupts disabled, and running |
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* local_bh_enable() with local interrupts disabled is an error - we'll run |
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* softirq callbacks, and they can unconditionally enable interrupts, and |
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* the caller of free_uid() didn't expect that.. |
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*/ |
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static DEFINE_SPINLOCK(uidhash_lock); |
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/* root_user.__count is 1, for init task cred */ |
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struct user_struct root_user = { |
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.__count = REFCOUNT_INIT(1), |
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.uid = GLOBAL_ROOT_UID, |
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.ratelimit = RATELIMIT_STATE_INIT(root_user.ratelimit, 0, 0), |
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}; |
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/* |
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* These routines must be called with the uidhash spinlock held! |
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*/ |
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static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent) |
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{ |
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hlist_add_head(&up->uidhash_node, hashent); |
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} |
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static void uid_hash_remove(struct user_struct *up) |
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{ |
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hlist_del_init(&up->uidhash_node); |
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} |
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static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent) |
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{ |
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struct user_struct *user; |
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hlist_for_each_entry(user, hashent, uidhash_node) { |
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if (uid_eq(user->uid, uid)) { |
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refcount_inc(&user->__count); |
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return user; |
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} |
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} |
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return NULL; |
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} |
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static int user_epoll_alloc(struct user_struct *up) |
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{ |
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#ifdef CONFIG_EPOLL |
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return percpu_counter_init(&up->epoll_watches, 0, GFP_KERNEL); |
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#else |
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return 0; |
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#endif |
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} |
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static void user_epoll_free(struct user_struct *up) |
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{ |
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#ifdef CONFIG_EPOLL |
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percpu_counter_destroy(&up->epoll_watches); |
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#endif |
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} |
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/* IRQs are disabled and uidhash_lock is held upon function entry. |
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* IRQ state (as stored in flags) is restored and uidhash_lock released |
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* upon function exit. |
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*/ |
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static void free_user(struct user_struct *up, unsigned long flags) |
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__releases(&uidhash_lock) |
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{ |
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uid_hash_remove(up); |
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spin_unlock_irqrestore(&uidhash_lock, flags); |
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user_epoll_free(up); |
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kmem_cache_free(uid_cachep, up); |
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} |
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/* |
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* Locate the user_struct for the passed UID. If found, take a ref on it. The |
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* caller must undo that ref with free_uid(). |
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* |
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* If the user_struct could not be found, return NULL. |
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*/ |
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struct user_struct *find_user(kuid_t uid) |
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{ |
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struct user_struct *ret; |
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unsigned long flags; |
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spin_lock_irqsave(&uidhash_lock, flags); |
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ret = uid_hash_find(uid, uidhashentry(uid)); |
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spin_unlock_irqrestore(&uidhash_lock, flags); |
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return ret; |
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} |
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void free_uid(struct user_struct *up) |
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{ |
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unsigned long flags; |
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if (!up) |
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return; |
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if (refcount_dec_and_lock_irqsave(&up->__count, &uidhash_lock, &flags)) |
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free_user(up, flags); |
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} |
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struct user_struct *alloc_uid(kuid_t uid) |
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{ |
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struct hlist_head *hashent = uidhashentry(uid); |
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struct user_struct *up, *new; |
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spin_lock_irq(&uidhash_lock); |
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up = uid_hash_find(uid, hashent); |
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spin_unlock_irq(&uidhash_lock); |
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if (!up) { |
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new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL); |
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if (!new) |
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return NULL; |
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new->uid = uid; |
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refcount_set(&new->__count, 1); |
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if (user_epoll_alloc(new)) { |
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kmem_cache_free(uid_cachep, new); |
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return NULL; |
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} |
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ratelimit_state_init(&new->ratelimit, HZ, 100); |
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ratelimit_set_flags(&new->ratelimit, RATELIMIT_MSG_ON_RELEASE); |
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/* |
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* Before adding this, check whether we raced |
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* on adding the same user already.. |
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*/ |
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spin_lock_irq(&uidhash_lock); |
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up = uid_hash_find(uid, hashent); |
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if (up) { |
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user_epoll_free(new); |
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kmem_cache_free(uid_cachep, new); |
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} else { |
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uid_hash_insert(new, hashent); |
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up = new; |
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} |
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spin_unlock_irq(&uidhash_lock); |
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} |
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return up; |
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} |
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static int __init uid_cache_init(void) |
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{ |
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int n; |
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uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct), |
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0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); |
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for(n = 0; n < UIDHASH_SZ; ++n) |
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INIT_HLIST_HEAD(uidhash_table + n); |
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if (user_epoll_alloc(&root_user)) |
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panic("root_user epoll percpu counter alloc failed"); |
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/* Insert the root user immediately (init already runs as root) */ |
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spin_lock_irq(&uidhash_lock); |
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uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID)); |
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spin_unlock_irq(&uidhash_lock); |
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return 0; |
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} |
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subsys_initcall(uid_cache_init);
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