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