| // 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> |
| |
| /* |
| * 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) |
| { |
| 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; |
| } |
| |
| 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); |
| } |
| |
| 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); |
| 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); |