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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> |
1da177e4 | 19 | |
59607db3 SH |
20 | /* |
21 | * userns count is 1 for root user, 1 for init_uts_ns, | |
22 | * and 1 for... ? | |
23 | */ | |
aee16ce7 PE |
24 | struct user_namespace init_user_ns = { |
25 | .kref = { | |
59607db3 | 26 | .refcount = ATOMIC_INIT(3), |
aee16ce7 | 27 | }, |
18b6e041 | 28 | .creator = &root_user, |
aee16ce7 PE |
29 | }; |
30 | EXPORT_SYMBOL_GPL(init_user_ns); | |
31 | ||
1da177e4 LT |
32 | /* |
33 | * UID task count cache, to get fast user lookup in "alloc_uid" | |
34 | * when changing user ID's (ie setuid() and friends). | |
35 | */ | |
36 | ||
7b44ab97 EB |
37 | #define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7) |
38 | #define UIDHASH_SZ (1 << UIDHASH_BITS) | |
1da177e4 LT |
39 | #define UIDHASH_MASK (UIDHASH_SZ - 1) |
40 | #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK) | |
7b44ab97 | 41 | #define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid)))) |
1da177e4 | 42 | |
e18b890b | 43 | static struct kmem_cache *uid_cachep; |
7b44ab97 | 44 | struct hlist_head uidhash_table[UIDHASH_SZ]; |
4021cb27 IM |
45 | |
46 | /* | |
47 | * The uidhash_lock is mostly taken from process context, but it is | |
48 | * occasionally also taken from softirq/tasklet context, when | |
49 | * task-structs get RCU-freed. Hence all locking must be softirq-safe. | |
3fa97c9d AM |
50 | * But free_uid() is also called with local interrupts disabled, and running |
51 | * local_bh_enable() with local interrupts disabled is an error - we'll run | |
52 | * softirq callbacks, and they can unconditionally enable interrupts, and | |
53 | * the caller of free_uid() didn't expect that.. | |
4021cb27 | 54 | */ |
1da177e4 LT |
55 | static DEFINE_SPINLOCK(uidhash_lock); |
56 | ||
59607db3 | 57 | /* root_user.__count is 2, 1 for init task cred, 1 for init_user_ns->user_ns */ |
1da177e4 | 58 | struct user_struct root_user = { |
18b6e041 | 59 | .__count = ATOMIC_INIT(2), |
1da177e4 LT |
60 | .processes = ATOMIC_INIT(1), |
61 | .files = ATOMIC_INIT(0), | |
62 | .sigpending = ATOMIC_INIT(0), | |
1da177e4 | 63 | .locked_shm = 0, |
7b44ab97 | 64 | .uid = GLOBAL_ROOT_UID, |
1da177e4 LT |
65 | }; |
66 | ||
5cb350ba DG |
67 | /* |
68 | * These routines must be called with the uidhash spinlock held! | |
69 | */ | |
40aeb400 | 70 | static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent) |
5cb350ba DG |
71 | { |
72 | hlist_add_head(&up->uidhash_node, hashent); | |
73 | } | |
74 | ||
40aeb400 | 75 | static void uid_hash_remove(struct user_struct *up) |
5cb350ba DG |
76 | { |
77 | hlist_del_init(&up->uidhash_node); | |
78 | } | |
79 | ||
7b44ab97 | 80 | static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent) |
3959214f KS |
81 | { |
82 | struct user_struct *user; | |
83 | struct hlist_node *h; | |
84 | ||
85 | hlist_for_each_entry(user, h, hashent, uidhash_node) { | |
7b44ab97 | 86 | if (uid_eq(user->uid, uid)) { |
3959214f KS |
87 | atomic_inc(&user->__count); |
88 | return user; | |
89 | } | |
90 | } | |
91 | ||
92 | return NULL; | |
93 | } | |
94 | ||
5cb350ba DG |
95 | /* IRQs are disabled and uidhash_lock is held upon function entry. |
96 | * IRQ state (as stored in flags) is restored and uidhash_lock released | |
97 | * upon function exit. | |
98 | */ | |
18b6e041 | 99 | static void free_user(struct user_struct *up, unsigned long flags) |
571428be | 100 | __releases(&uidhash_lock) |
5cb350ba DG |
101 | { |
102 | uid_hash_remove(up); | |
103 | spin_unlock_irqrestore(&uidhash_lock, flags); | |
5cb350ba DG |
104 | key_put(up->uid_keyring); |
105 | key_put(up->session_keyring); | |
106 | kmem_cache_free(uid_cachep, up); | |
107 | } | |
108 | ||
1da177e4 LT |
109 | /* |
110 | * Locate the user_struct for the passed UID. If found, take a ref on it. The | |
111 | * caller must undo that ref with free_uid(). | |
112 | * | |
113 | * If the user_struct could not be found, return NULL. | |
114 | */ | |
7b44ab97 | 115 | struct user_struct *find_user(kuid_t uid) |
1da177e4 LT |
116 | { |
117 | struct user_struct *ret; | |
3fa97c9d | 118 | unsigned long flags; |
1da177e4 | 119 | |
3fa97c9d | 120 | spin_lock_irqsave(&uidhash_lock, flags); |
7b44ab97 | 121 | ret = uid_hash_find(uid, uidhashentry(uid)); |
3fa97c9d | 122 | spin_unlock_irqrestore(&uidhash_lock, flags); |
1da177e4 LT |
123 | return ret; |
124 | } | |
125 | ||
126 | void free_uid(struct user_struct *up) | |
127 | { | |
3fa97c9d AM |
128 | unsigned long flags; |
129 | ||
36f57413 AM |
130 | if (!up) |
131 | return; | |
132 | ||
3fa97c9d | 133 | local_irq_save(flags); |
5cb350ba DG |
134 | if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) |
135 | free_user(up, flags); | |
136 | else | |
36f57413 | 137 | local_irq_restore(flags); |
1da177e4 LT |
138 | } |
139 | ||
7b44ab97 | 140 | struct user_struct *alloc_uid(kuid_t uid) |
1da177e4 | 141 | { |
7b44ab97 | 142 | struct hlist_head *hashent = uidhashentry(uid); |
8eb703e4 | 143 | struct user_struct *up, *new; |
1da177e4 | 144 | |
3fa97c9d | 145 | spin_lock_irq(&uidhash_lock); |
1da177e4 | 146 | up = uid_hash_find(uid, hashent); |
3fa97c9d | 147 | spin_unlock_irq(&uidhash_lock); |
1da177e4 LT |
148 | |
149 | if (!up) { | |
354a1f4d | 150 | new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL); |
8eb703e4 PE |
151 | if (!new) |
152 | goto out_unlock; | |
5e8869bb | 153 | |
1da177e4 LT |
154 | new->uid = uid; |
155 | atomic_set(&new->__count, 1); | |
1da177e4 LT |
156 | |
157 | /* | |
158 | * Before adding this, check whether we raced | |
159 | * on adding the same user already.. | |
160 | */ | |
3fa97c9d | 161 | spin_lock_irq(&uidhash_lock); |
1da177e4 LT |
162 | up = uid_hash_find(uid, hashent); |
163 | if (up) { | |
164 | key_put(new->uid_keyring); | |
165 | key_put(new->session_keyring); | |
166 | kmem_cache_free(uid_cachep, new); | |
167 | } else { | |
168 | uid_hash_insert(new, hashent); | |
169 | up = new; | |
170 | } | |
3fa97c9d | 171 | spin_unlock_irq(&uidhash_lock); |
1da177e4 | 172 | } |
5cb350ba | 173 | |
1da177e4 | 174 | return up; |
8eb703e4 | 175 | |
8eb703e4 | 176 | out_unlock: |
8eb703e4 | 177 | return NULL; |
1da177e4 LT |
178 | } |
179 | ||
1da177e4 LT |
180 | static int __init uid_cache_init(void) |
181 | { | |
182 | int n; | |
183 | ||
184 | uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct), | |
20c2df83 | 185 | 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); |
1da177e4 LT |
186 | |
187 | for(n = 0; n < UIDHASH_SZ; ++n) | |
7b44ab97 | 188 | INIT_HLIST_HEAD(uidhash_table + n); |
1da177e4 LT |
189 | |
190 | /* Insert the root user immediately (init already runs as root) */ | |
3fa97c9d | 191 | spin_lock_irq(&uidhash_lock); |
7b44ab97 | 192 | uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID)); |
3fa97c9d | 193 | spin_unlock_irq(&uidhash_lock); |
1da177e4 LT |
194 | |
195 | return 0; | |
196 | } | |
197 | ||
198 | module_init(uid_cache_init); |