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