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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
1da177e4 LT |
2 | /* |
3 | * The "user cache". | |
4 | * | |
5 | * (C) Copyright 1991-2000 Linus Torvalds | |
6 | * | |
7 | * We have a per-user structure to keep track of how many | |
8 | * processes, files etc the user has claimed, in order to be | |
9 | * able to have per-user limits for system resources. | |
10 | */ | |
11 | ||
12 | #include <linux/init.h> | |
13 | #include <linux/sched.h> | |
14 | #include <linux/slab.h> | |
15 | #include <linux/bitops.h> | |
16 | #include <linux/key.h> | |
8703e8a4 | 17 | #include <linux/sched/user.h> |
4021cb27 | 18 | #include <linux/interrupt.h> |
9984de1a | 19 | #include <linux/export.h> |
acce292c | 20 | #include <linux/user_namespace.h> |
21ca59b3 | 21 | #include <linux/binfmts.h> |
0bb80f24 | 22 | #include <linux/proc_ns.h> |
1da177e4 | 23 | |
21ca59b3 CB |
24 | #if IS_ENABLED(CONFIG_BINFMT_MISC) |
25 | struct binfmt_misc init_binfmt_misc = { | |
26 | .entries = LIST_HEAD_INIT(init_binfmt_misc.entries), | |
27 | .enabled = true, | |
28 | .entries_lock = __RW_LOCK_UNLOCKED(init_binfmt_misc.entries_lock), | |
29 | }; | |
30 | EXPORT_SYMBOL_GPL(init_binfmt_misc); | |
31 | #endif | |
32 | ||
59607db3 SH |
33 | /* |
34 | * userns count is 1 for root user, 1 for init_uts_ns, | |
35 | * and 1 for... ? | |
36 | */ | |
aee16ce7 | 37 | struct user_namespace init_user_ns = { |
22d917d8 EB |
38 | .uid_map = { |
39 | .nr_extents = 1, | |
aa4bf44d CB |
40 | { |
41 | .extent[0] = { | |
42 | .first = 0, | |
43 | .lower_first = 0, | |
44 | .count = 4294967295U, | |
45 | }, | |
22d917d8 EB |
46 | }, |
47 | }, | |
48 | .gid_map = { | |
49 | .nr_extents = 1, | |
aa4bf44d CB |
50 | { |
51 | .extent[0] = { | |
52 | .first = 0, | |
53 | .lower_first = 0, | |
54 | .count = 4294967295U, | |
55 | }, | |
22d917d8 EB |
56 | }, |
57 | }, | |
f76d207a EB |
58 | .projid_map = { |
59 | .nr_extents = 1, | |
aa4bf44d CB |
60 | { |
61 | .extent[0] = { | |
62 | .first = 0, | |
63 | .lower_first = 0, | |
64 | .count = 4294967295U, | |
65 | }, | |
f76d207a EB |
66 | }, |
67 | }, | |
265cbd62 | 68 | .ns.count = REFCOUNT_INIT(3), |
783291e6 EB |
69 | .owner = GLOBAL_ROOT_UID, |
70 | .group = GLOBAL_ROOT_GID, | |
435d5f4b | 71 | .ns.inum = PROC_USER_INIT_INO, |
33c42940 AV |
72 | #ifdef CONFIG_USER_NS |
73 | .ns.ops = &userns_operations, | |
74 | #endif | |
9cc46516 | 75 | .flags = USERNS_INIT_FLAGS, |
b206f281 DH |
76 | #ifdef CONFIG_KEYS |
77 | .keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list), | |
0f44e4d9 | 78 | .keyring_sem = __RWSEM_INITIALIZER(init_user_ns.keyring_sem), |
f36f8c75 | 79 | #endif |
21ca59b3 CB |
80 | #if IS_ENABLED(CONFIG_BINFMT_MISC) |
81 | .binfmt_misc = &init_binfmt_misc, | |
82 | #endif | |
aee16ce7 PE |
83 | }; |
84 | EXPORT_SYMBOL_GPL(init_user_ns); | |
85 | ||
1da177e4 LT |
86 | /* |
87 | * UID task count cache, to get fast user lookup in "alloc_uid" | |
88 | * when changing user ID's (ie setuid() and friends). | |
89 | */ | |
90 | ||
7b44ab97 EB |
91 | #define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7) |
92 | #define UIDHASH_SZ (1 << UIDHASH_BITS) | |
1da177e4 LT |
93 | #define UIDHASH_MASK (UIDHASH_SZ - 1) |
94 | #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK) | |
7b44ab97 | 95 | #define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid)))) |
1da177e4 | 96 | |
e18b890b | 97 | static struct kmem_cache *uid_cachep; |
de83dbd9 | 98 | static struct hlist_head uidhash_table[UIDHASH_SZ]; |
4021cb27 IM |
99 | |
100 | /* | |
101 | * The uidhash_lock is mostly taken from process context, but it is | |
102 | * occasionally also taken from softirq/tasklet context, when | |
103 | * task-structs get RCU-freed. Hence all locking must be softirq-safe. | |
3fa97c9d AM |
104 | * But free_uid() is also called with local interrupts disabled, and running |
105 | * local_bh_enable() with local interrupts disabled is an error - we'll run | |
106 | * softirq callbacks, and they can unconditionally enable interrupts, and | |
107 | * the caller of free_uid() didn't expect that.. | |
4021cb27 | 108 | */ |
1da177e4 LT |
109 | static DEFINE_SPINLOCK(uidhash_lock); |
110 | ||
783291e6 | 111 | /* root_user.__count is 1, for init task cred */ |
1da177e4 | 112 | struct user_struct root_user = { |
fc371912 | 113 | .__count = REFCOUNT_INIT(1), |
7b44ab97 | 114 | .uid = GLOBAL_ROOT_UID, |
bef3efbe | 115 | .ratelimit = RATELIMIT_STATE_INIT(root_user.ratelimit, 0, 0), |
1da177e4 LT |
116 | }; |
117 | ||
5cb350ba DG |
118 | /* |
119 | * These routines must be called with the uidhash spinlock held! | |
120 | */ | |
40aeb400 | 121 | static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent) |
5cb350ba DG |
122 | { |
123 | hlist_add_head(&up->uidhash_node, hashent); | |
124 | } | |
125 | ||
40aeb400 | 126 | static void uid_hash_remove(struct user_struct *up) |
5cb350ba DG |
127 | { |
128 | hlist_del_init(&up->uidhash_node); | |
129 | } | |
130 | ||
7b44ab97 | 131 | static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent) |
3959214f KS |
132 | { |
133 | struct user_struct *user; | |
3959214f | 134 | |
b67bfe0d | 135 | hlist_for_each_entry(user, hashent, uidhash_node) { |
7b44ab97 | 136 | if (uid_eq(user->uid, uid)) { |
fc371912 | 137 | refcount_inc(&user->__count); |
3959214f KS |
138 | return user; |
139 | } | |
140 | } | |
141 | ||
142 | return NULL; | |
143 | } | |
144 | ||
1e1c1583 NP |
145 | static int user_epoll_alloc(struct user_struct *up) |
146 | { | |
147 | #ifdef CONFIG_EPOLL | |
148 | return percpu_counter_init(&up->epoll_watches, 0, GFP_KERNEL); | |
149 | #else | |
150 | return 0; | |
151 | #endif | |
152 | } | |
153 | ||
154 | static void user_epoll_free(struct user_struct *up) | |
155 | { | |
156 | #ifdef CONFIG_EPOLL | |
157 | percpu_counter_destroy(&up->epoll_watches); | |
158 | #endif | |
159 | } | |
160 | ||
5cb350ba DG |
161 | /* IRQs are disabled and uidhash_lock is held upon function entry. |
162 | * IRQ state (as stored in flags) is restored and uidhash_lock released | |
163 | * upon function exit. | |
164 | */ | |
18b6e041 | 165 | static void free_user(struct user_struct *up, unsigned long flags) |
571428be | 166 | __releases(&uidhash_lock) |
5cb350ba DG |
167 | { |
168 | uid_hash_remove(up); | |
169 | spin_unlock_irqrestore(&uidhash_lock, flags); | |
1e1c1583 | 170 | user_epoll_free(up); |
5cb350ba DG |
171 | kmem_cache_free(uid_cachep, up); |
172 | } | |
173 | ||
1da177e4 LT |
174 | /* |
175 | * Locate the user_struct for the passed UID. If found, take a ref on it. The | |
176 | * caller must undo that ref with free_uid(). | |
177 | * | |
178 | * If the user_struct could not be found, return NULL. | |
179 | */ | |
7b44ab97 | 180 | struct user_struct *find_user(kuid_t uid) |
1da177e4 LT |
181 | { |
182 | struct user_struct *ret; | |
3fa97c9d | 183 | unsigned long flags; |
1da177e4 | 184 | |
3fa97c9d | 185 | spin_lock_irqsave(&uidhash_lock, flags); |
7b44ab97 | 186 | ret = uid_hash_find(uid, uidhashentry(uid)); |
3fa97c9d | 187 | spin_unlock_irqrestore(&uidhash_lock, flags); |
1da177e4 LT |
188 | return ret; |
189 | } | |
190 | ||
191 | void free_uid(struct user_struct *up) | |
192 | { | |
3fa97c9d AM |
193 | unsigned long flags; |
194 | ||
36f57413 AM |
195 | if (!up) |
196 | return; | |
197 | ||
ce0a568d | 198 | if (refcount_dec_and_lock_irqsave(&up->__count, &uidhash_lock, &flags)) |
5cb350ba | 199 | free_user(up, flags); |
1da177e4 | 200 | } |
ce5a23c8 | 201 | EXPORT_SYMBOL_GPL(free_uid); |
1da177e4 | 202 | |
7b44ab97 | 203 | struct user_struct *alloc_uid(kuid_t uid) |
1da177e4 | 204 | { |
7b44ab97 | 205 | struct hlist_head *hashent = uidhashentry(uid); |
8eb703e4 | 206 | struct user_struct *up, *new; |
1da177e4 | 207 | |
3fa97c9d | 208 | spin_lock_irq(&uidhash_lock); |
1da177e4 | 209 | up = uid_hash_find(uid, hashent); |
3fa97c9d | 210 | spin_unlock_irq(&uidhash_lock); |
1da177e4 LT |
211 | |
212 | if (!up) { | |
354a1f4d | 213 | new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL); |
8eb703e4 | 214 | if (!new) |
6c4e121f | 215 | return NULL; |
5e8869bb | 216 | |
1da177e4 | 217 | new->uid = uid; |
fc371912 | 218 | refcount_set(&new->__count, 1); |
1e1c1583 NP |
219 | if (user_epoll_alloc(new)) { |
220 | kmem_cache_free(uid_cachep, new); | |
221 | return NULL; | |
222 | } | |
bef3efbe LT |
223 | ratelimit_state_init(&new->ratelimit, HZ, 100); |
224 | ratelimit_set_flags(&new->ratelimit, RATELIMIT_MSG_ON_RELEASE); | |
1da177e4 LT |
225 | |
226 | /* | |
227 | * Before adding this, check whether we raced | |
228 | * on adding the same user already.. | |
229 | */ | |
3fa97c9d | 230 | spin_lock_irq(&uidhash_lock); |
1da177e4 LT |
231 | up = uid_hash_find(uid, hashent); |
232 | if (up) { | |
1e1c1583 | 233 | user_epoll_free(new); |
1da177e4 LT |
234 | kmem_cache_free(uid_cachep, new); |
235 | } else { | |
236 | uid_hash_insert(new, hashent); | |
237 | up = new; | |
238 | } | |
3fa97c9d | 239 | spin_unlock_irq(&uidhash_lock); |
1da177e4 | 240 | } |
5cb350ba | 241 | |
1da177e4 LT |
242 | return up; |
243 | } | |
244 | ||
1da177e4 LT |
245 | static int __init uid_cache_init(void) |
246 | { | |
247 | int n; | |
248 | ||
249 | uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct), | |
20c2df83 | 250 | 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); |
1da177e4 LT |
251 | |
252 | for(n = 0; n < UIDHASH_SZ; ++n) | |
7b44ab97 | 253 | INIT_HLIST_HEAD(uidhash_table + n); |
1da177e4 | 254 | |
1e1c1583 NP |
255 | if (user_epoll_alloc(&root_user)) |
256 | panic("root_user epoll percpu counter alloc failed"); | |
257 | ||
1da177e4 | 258 | /* Insert the root user immediately (init already runs as root) */ |
3fa97c9d | 259 | spin_lock_irq(&uidhash_lock); |
7b44ab97 | 260 | uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID)); |
3fa97c9d | 261 | spin_unlock_irq(&uidhash_lock); |
1da177e4 LT |
262 | |
263 | return 0; | |
264 | } | |
c96d6660 | 265 | subsys_initcall(uid_cache_init); |