blob: 71dd2363ab0f66dcbb2a3574d7b977af08369bea [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * The "user cache".
3 *
4 * (C) Copyright 1991-2000 Linus Torvalds
5 *
6 * We have a per-user structure to keep track of how many
7 * processes, files etc the user has claimed, in order to be
8 * able to have per-user limits for system resources.
9 */
10
11#include <linux/init.h>
12#include <linux/sched.h>
13#include <linux/slab.h>
14#include <linux/bitops.h>
15#include <linux/key.h>
Ingo Molnar4021cb22006-01-25 15:23:07 +010016#include <linux/interrupt.h>
Paul Gortmaker9984de12011-05-23 14:51:41 -040017#include <linux/export.h>
Cedric Le Goateracce2922007-07-15 23:40:59 -070018#include <linux/user_namespace.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070019
Serge E. Hallyn59607db2011-03-23 16:43:16 -070020/*
21 * userns count is 1 for root user, 1 for init_uts_ns,
22 * and 1 for... ?
23 */
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080024struct user_namespace init_user_ns = {
25 .kref = {
Serge E. Hallyn59607db2011-03-23 16:43:16 -070026 .refcount = ATOMIC_INIT(3),
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080027 },
Serge Hallyn18b6e042008-10-15 16:38:45 -050028 .creator = &root_user,
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080029};
30EXPORT_SYMBOL_GPL(init_user_ns);
31
Linus Torvalds1da177e2005-04-16 15:20:36 -070032/*
33 * UID task count cache, to get fast user lookup in "alloc_uid"
34 * when changing user ID's (ie setuid() and friends).
35 */
36
Linus Torvalds1da177e2005-04-16 15:20:36 -070037#define UIDHASH_MASK (UIDHASH_SZ - 1)
38#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
Cedric Le Goateracce2922007-07-15 23:40:59 -070039#define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid)))
Linus Torvalds1da177e2005-04-16 15:20:36 -070040
Christoph Lametere18b8902006-12-06 20:33:20 -080041static struct kmem_cache *uid_cachep;
Ingo Molnar4021cb22006-01-25 15:23:07 +010042
43/*
44 * The uidhash_lock is mostly taken from process context, but it is
45 * occasionally also taken from softirq/tasklet context, when
46 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
Andrew Morton3fa97c92006-01-31 16:34:26 -080047 * But free_uid() is also called with local interrupts disabled, and running
48 * local_bh_enable() with local interrupts disabled is an error - we'll run
49 * softirq callbacks, and they can unconditionally enable interrupts, and
50 * the caller of free_uid() didn't expect that..
Ingo Molnar4021cb22006-01-25 15:23:07 +010051 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070052static DEFINE_SPINLOCK(uidhash_lock);
53
Serge E. Hallyn59607db2011-03-23 16:43:16 -070054/* root_user.__count is 2, 1 for init task cred, 1 for init_user_ns->user_ns */
Linus Torvalds1da177e2005-04-16 15:20:36 -070055struct user_struct root_user = {
Serge Hallyn18b6e042008-10-15 16:38:45 -050056 .__count = ATOMIC_INIT(2),
Linus Torvalds1da177e2005-04-16 15:20:36 -070057 .processes = ATOMIC_INIT(1),
58 .files = ATOMIC_INIT(0),
59 .sigpending = ATOMIC_INIT(0),
Linus Torvalds1da177e2005-04-16 15:20:36 -070060 .locked_shm = 0,
Serge Hallyn18b6e042008-10-15 16:38:45 -050061 .user_ns = &init_user_ns,
Linus Torvalds1da177e2005-04-16 15:20:36 -070062};
63
Dhaval Giani5cb350b2007-10-15 17:00:14 +020064/*
65 * These routines must be called with the uidhash spinlock held!
66 */
Alexey Dobriyan40aeb402007-10-16 23:30:09 -070067static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
Dhaval Giani5cb350b2007-10-15 17:00:14 +020068{
69 hlist_add_head(&up->uidhash_node, hashent);
70}
71
Alexey Dobriyan40aeb402007-10-16 23:30:09 -070072static void uid_hash_remove(struct user_struct *up)
Dhaval Giani5cb350b2007-10-15 17:00:14 +020073{
74 hlist_del_init(&up->uidhash_node);
Serge E. Hallynfb5ae642009-02-13 14:04:21 +000075 put_user_ns(up->user_ns);
Dhaval Giani5cb350b2007-10-15 17:00:14 +020076}
77
Kay Sievers39592142009-03-24 15:43:30 +010078static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
79{
80 struct user_struct *user;
81 struct hlist_node *h;
82
83 hlist_for_each_entry(user, h, hashent, uidhash_node) {
84 if (user->uid == uid) {
85 atomic_inc(&user->__count);
86 return user;
87 }
88 }
89
90 return NULL;
91}
92
Dhaval Giani5cb350b2007-10-15 17:00:14 +020093/* IRQs are disabled and uidhash_lock is held upon function entry.
94 * IRQ state (as stored in flags) is restored and uidhash_lock released
95 * upon function exit.
96 */
Serge Hallyn18b6e042008-10-15 16:38:45 -050097static void free_user(struct user_struct *up, unsigned long flags)
Namhyung Kim571428b2010-10-26 14:22:43 -070098 __releases(&uidhash_lock)
Dhaval Giani5cb350b2007-10-15 17:00:14 +020099{
100 uid_hash_remove(up);
101 spin_unlock_irqrestore(&uidhash_lock, flags);
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200102 key_put(up->uid_keyring);
103 key_put(up->session_keyring);
104 kmem_cache_free(uid_cachep, up);
105}
Srivatsa Vaddagiri24e377a2007-10-15 17:00:09 +0200106
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108 * Locate the user_struct for the passed UID. If found, take a ref on it. The
109 * caller must undo that ref with free_uid().
110 *
111 * If the user_struct could not be found, return NULL.
112 */
113struct user_struct *find_user(uid_t uid)
114{
115 struct user_struct *ret;
Andrew Morton3fa97c92006-01-31 16:34:26 -0800116 unsigned long flags;
Serge Hallyn6ded6ab2008-11-24 16:24:10 -0500117 struct user_namespace *ns = current_user_ns();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118
Andrew Morton3fa97c92006-01-31 16:34:26 -0800119 spin_lock_irqsave(&uidhash_lock, flags);
Cedric Le Goateracce2922007-07-15 23:40:59 -0700120 ret = uid_hash_find(uid, uidhashentry(ns, uid));
Andrew Morton3fa97c92006-01-31 16:34:26 -0800121 spin_unlock_irqrestore(&uidhash_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700122 return ret;
123}
124
125void free_uid(struct user_struct *up)
126{
Andrew Morton3fa97c92006-01-31 16:34:26 -0800127 unsigned long flags;
128
Andrew Morton36f57412006-03-24 03:15:47 -0800129 if (!up)
130 return;
131
Andrew Morton3fa97c92006-01-31 16:34:26 -0800132 local_irq_save(flags);
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200133 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
134 free_user(up, flags);
135 else
Andrew Morton36f57412006-03-24 03:15:47 -0800136 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700137}
138
Andrew Morton354a1f42008-04-30 00:54:54 -0700139struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140{
Pavel Emelyanov735de222007-09-18 22:46:44 -0700141 struct hlist_head *hashent = uidhashentry(ns, uid);
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100142 struct user_struct *up, *new;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143
Andrew Morton3fa97c92006-01-31 16:34:26 -0800144 spin_lock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145 up = uid_hash_find(uid, hashent);
Andrew Morton3fa97c92006-01-31 16:34:26 -0800146 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147
148 if (!up) {
Andrew Morton354a1f42008-04-30 00:54:54 -0700149 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100150 if (!new)
151 goto out_unlock;
Pavel Emelyanov5e8869b2007-11-26 21:21:49 +0100152
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153 new->uid = uid;
154 atomic_set(&new->__count, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155
Serge Hallyn18b6e042008-10-15 16:38:45 -0500156 new->user_ns = get_user_ns(ns);
157
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158 /*
159 * Before adding this, check whether we raced
160 * on adding the same user already..
161 */
Andrew Morton3fa97c92006-01-31 16:34:26 -0800162 spin_lock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163 up = uid_hash_find(uid, hashent);
164 if (up) {
Hillf Danton4ef9e112010-12-29 21:55:28 +0800165 put_user_ns(ns);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166 key_put(new->uid_keyring);
167 key_put(new->session_keyring);
168 kmem_cache_free(uid_cachep, new);
169 } else {
170 uid_hash_insert(new, hashent);
171 up = new;
172 }
Andrew Morton3fa97c92006-01-31 16:34:26 -0800173 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174 }
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200175
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176 return up;
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100177
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100178out_unlock:
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100179 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180}
181
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182static int __init uid_cache_init(void)
183{
184 int n;
185
186 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
Paul Mundt20c2df82007-07-20 10:11:58 +0900187 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188
189 for(n = 0; n < UIDHASH_SZ; ++n)
Pavel Emelyanov735de222007-09-18 22:46:44 -0700190 INIT_HLIST_HEAD(init_user_ns.uidhash_table + n);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191
192 /* Insert the root user immediately (init already runs as root) */
Andrew Morton3fa97c92006-01-31 16:34:26 -0800193 spin_lock_irq(&uidhash_lock);
Cedric Le Goateracce2922007-07-15 23:40:59 -0700194 uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
Andrew Morton3fa97c92006-01-31 16:34:26 -0800195 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196
197 return 0;
198}
199
200module_init(uid_cache_init);