Merge remote-tracking branch 'rcu/rcu/next'
[deliverable/linux.git] / kernel / user.c
CommitLineData
1da177e4
LT
1/*
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>
4021cb27 16#include <linux/interrupt.h>
9984de1a 17#include <linux/export.h>
acce292c 18#include <linux/user_namespace.h>
0bb80f24 19#include <linux/proc_ns.h>
1da177e4 20
59607db3
SH
21/*
22 * userns count is 1 for root user, 1 for init_uts_ns,
23 * and 1 for... ?
24 */
aee16ce7 25struct user_namespace init_user_ns = {
22d917d8
EB
26 .uid_map = {
27 .nr_extents = 1,
28 .extent[0] = {
29 .first = 0,
30 .lower_first = 0,
4b06a81f 31 .count = 4294967295U,
22d917d8
EB
32 },
33 },
34 .gid_map = {
35 .nr_extents = 1,
36 .extent[0] = {
37 .first = 0,
38 .lower_first = 0,
4b06a81f 39 .count = 4294967295U,
22d917d8
EB
40 },
41 },
f76d207a
EB
42 .projid_map = {
43 .nr_extents = 1,
44 .extent[0] = {
45 .first = 0,
46 .lower_first = 0,
47 .count = 4294967295U,
48 },
49 },
c61a2810 50 .count = ATOMIC_INIT(3),
783291e6
EB
51 .owner = GLOBAL_ROOT_UID,
52 .group = GLOBAL_ROOT_GID,
435d5f4b 53 .ns.inum = PROC_USER_INIT_INO,
33c42940
AV
54#ifdef CONFIG_USER_NS
55 .ns.ops = &userns_operations,
56#endif
9cc46516 57 .flags = USERNS_INIT_FLAGS,
6bd364d8
XG
58#ifdef CONFIG_PERSISTENT_KEYRINGS
59 .persistent_keyring_register_sem =
60 __RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),
f36f8c75 61#endif
aee16ce7
PE
62};
63EXPORT_SYMBOL_GPL(init_user_ns);
64
1da177e4
LT
65/*
66 * UID task count cache, to get fast user lookup in "alloc_uid"
67 * when changing user ID's (ie setuid() and friends).
68 */
69
7b44ab97
EB
70#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
71#define UIDHASH_SZ (1 << UIDHASH_BITS)
1da177e4
LT
72#define UIDHASH_MASK (UIDHASH_SZ - 1)
73#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
7b44ab97 74#define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid))))
1da177e4 75
e18b890b 76static struct kmem_cache *uid_cachep;
7b44ab97 77struct hlist_head uidhash_table[UIDHASH_SZ];
4021cb27
IM
78
79/*
80 * The uidhash_lock is mostly taken from process context, but it is
81 * occasionally also taken from softirq/tasklet context, when
82 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
3fa97c9d
AM
83 * But free_uid() is also called with local interrupts disabled, and running
84 * local_bh_enable() with local interrupts disabled is an error - we'll run
85 * softirq callbacks, and they can unconditionally enable interrupts, and
86 * the caller of free_uid() didn't expect that..
4021cb27 87 */
1da177e4
LT
88static DEFINE_SPINLOCK(uidhash_lock);
89
783291e6 90/* root_user.__count is 1, for init task cred */
1da177e4 91struct user_struct root_user = {
783291e6 92 .__count = ATOMIC_INIT(1),
1da177e4 93 .processes = ATOMIC_INIT(1),
1da177e4 94 .sigpending = ATOMIC_INIT(0),
1da177e4 95 .locked_shm = 0,
7b44ab97 96 .uid = GLOBAL_ROOT_UID,
1da177e4
LT
97};
98
5cb350ba
DG
99/*
100 * These routines must be called with the uidhash spinlock held!
101 */
40aeb400 102static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
5cb350ba
DG
103{
104 hlist_add_head(&up->uidhash_node, hashent);
105}
106
40aeb400 107static void uid_hash_remove(struct user_struct *up)
5cb350ba
DG
108{
109 hlist_del_init(&up->uidhash_node);
110}
111
7b44ab97 112static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent)
3959214f
KS
113{
114 struct user_struct *user;
3959214f 115
b67bfe0d 116 hlist_for_each_entry(user, hashent, uidhash_node) {
7b44ab97 117 if (uid_eq(user->uid, uid)) {
3959214f
KS
118 atomic_inc(&user->__count);
119 return user;
120 }
121 }
122
123 return NULL;
124}
125
5cb350ba
DG
126/* IRQs are disabled and uidhash_lock is held upon function entry.
127 * IRQ state (as stored in flags) is restored and uidhash_lock released
128 * upon function exit.
129 */
18b6e041 130static void free_user(struct user_struct *up, unsigned long flags)
571428be 131 __releases(&uidhash_lock)
5cb350ba
DG
132{
133 uid_hash_remove(up);
134 spin_unlock_irqrestore(&uidhash_lock, flags);
5cb350ba
DG
135 key_put(up->uid_keyring);
136 key_put(up->session_keyring);
137 kmem_cache_free(uid_cachep, up);
138}
139
1da177e4
LT
140/*
141 * Locate the user_struct for the passed UID. If found, take a ref on it. The
142 * caller must undo that ref with free_uid().
143 *
144 * If the user_struct could not be found, return NULL.
145 */
7b44ab97 146struct user_struct *find_user(kuid_t uid)
1da177e4
LT
147{
148 struct user_struct *ret;
3fa97c9d 149 unsigned long flags;
1da177e4 150
3fa97c9d 151 spin_lock_irqsave(&uidhash_lock, flags);
7b44ab97 152 ret = uid_hash_find(uid, uidhashentry(uid));
3fa97c9d 153 spin_unlock_irqrestore(&uidhash_lock, flags);
1da177e4
LT
154 return ret;
155}
156
157void free_uid(struct user_struct *up)
158{
3fa97c9d
AM
159 unsigned long flags;
160
36f57413
AM
161 if (!up)
162 return;
163
3fa97c9d 164 local_irq_save(flags);
5cb350ba
DG
165 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
166 free_user(up, flags);
167 else
36f57413 168 local_irq_restore(flags);
1da177e4
LT
169}
170
7b44ab97 171struct user_struct *alloc_uid(kuid_t uid)
1da177e4 172{
7b44ab97 173 struct hlist_head *hashent = uidhashentry(uid);
8eb703e4 174 struct user_struct *up, *new;
1da177e4 175
3fa97c9d 176 spin_lock_irq(&uidhash_lock);
1da177e4 177 up = uid_hash_find(uid, hashent);
3fa97c9d 178 spin_unlock_irq(&uidhash_lock);
1da177e4
LT
179
180 if (!up) {
354a1f4d 181 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
8eb703e4
PE
182 if (!new)
183 goto out_unlock;
5e8869bb 184
1da177e4
LT
185 new->uid = uid;
186 atomic_set(&new->__count, 1);
1da177e4
LT
187
188 /*
189 * Before adding this, check whether we raced
190 * on adding the same user already..
191 */
3fa97c9d 192 spin_lock_irq(&uidhash_lock);
1da177e4
LT
193 up = uid_hash_find(uid, hashent);
194 if (up) {
195 key_put(new->uid_keyring);
196 key_put(new->session_keyring);
197 kmem_cache_free(uid_cachep, new);
198 } else {
199 uid_hash_insert(new, hashent);
200 up = new;
201 }
3fa97c9d 202 spin_unlock_irq(&uidhash_lock);
1da177e4 203 }
5cb350ba 204
1da177e4 205 return up;
8eb703e4 206
8eb703e4 207out_unlock:
8eb703e4 208 return NULL;
1da177e4
LT
209}
210
1da177e4
LT
211static int __init uid_cache_init(void)
212{
213 int n;
214
215 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
20c2df83 216 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1da177e4
LT
217
218 for(n = 0; n < UIDHASH_SZ; ++n)
7b44ab97 219 INIT_HLIST_HEAD(uidhash_table + n);
1da177e4
LT
220
221 /* Insert the root user immediately (init already runs as root) */
3fa97c9d 222 spin_lock_irq(&uidhash_lock);
7b44ab97 223 uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
3fa97c9d 224 spin_unlock_irq(&uidhash_lock);
1da177e4
LT
225
226 return 0;
227}
c96d6660 228subsys_initcall(uid_cache_init);
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