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 | |
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 | }; |
63 | EXPORT_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 | 76 | static struct kmem_cache *uid_cachep; |
7b44ab97 | 77 | struct 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 |
88 | static DEFINE_SPINLOCK(uidhash_lock); |
89 | ||
783291e6 | 90 | /* root_user.__count is 1, for init task cred */ |
1da177e4 | 91 | struct 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 | 102 | static 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 | 107 | static void uid_hash_remove(struct user_struct *up) |
5cb350ba DG |
108 | { |
109 | hlist_del_init(&up->uidhash_node); | |
110 | } | |
111 | ||
7b44ab97 | 112 | static 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 | 130 | static 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 | 146 | struct 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 | ||
157 | void 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 | 171 | struct 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 | 207 | out_unlock: |
8eb703e4 | 208 | return NULL; |
1da177e4 LT |
209 | } |
210 | ||
1da177e4 LT |
211 | static 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 | 228 | subsys_initcall(uid_cache_init); |