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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262// 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/binfmts.h>#include <linux/proc_ns.h>
#if IS_ENABLED(CONFIG_BINFMT_MISC)struct binfmt_misc init_binfmt_misc = { .entries = LIST_HEAD_INIT(init_binfmt_misc.entries), .enabled = true, .entries_lock = __RW_LOCK_UNLOCKED(init_binfmt_misc.entries_lock),};EXPORT_SYMBOL_GPL(init_binfmt_misc);#endif
/* * userns count is 1 for root user, 1 for init_uts_ns, * and 1 for... ? */struct user_namespace init_user_ns = { .ns = NS_COMMON_INIT(init_user_ns), .uid_map = { { .extent[0] = { .first = 0, .lower_first = 0, .count = 4294967295U, }, .nr_extents = 1, }, }, .gid_map = { { .extent[0] = { .first = 0, .lower_first = 0, .count = 4294967295U, }, .nr_extents = 1, }, }, .projid_map = { { .extent[0] = { .first = 0, .lower_first = 0, .count = 4294967295U, }, .nr_extents = 1, }, }, .owner = GLOBAL_ROOT_UID, .group = GLOBAL_ROOT_GID, .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#if IS_ENABLED(CONFIG_BINFMT_MISC) .binfmt_misc = &init_binfmt_misc,#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 (IS_ENABLED(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);}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); 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);