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