Merge branch 'fixes-for-3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/coolone...
[linux-2.6/luiz-linux-2.6.git] / kernel / user.c
blobb815fefbe76fa4743bd3081af6c6e469dff2f4db
1 /*
2 * The "user cache".
4 * (C) Copyright 1991-2000 Linus Torvalds
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 */
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>
16 #include <linux/interrupt.h>
17 #include <linux/export.h>
18 #include <linux/user_namespace.h>
21 * userns count is 1 for root user, 1 for init_uts_ns,
22 * and 1 for... ?
24 struct user_namespace init_user_ns = {
25 .uid_map = {
26 .nr_extents = 1,
27 .extent[0] = {
28 .first = 0,
29 .lower_first = 0,
30 .count = 4294967295U,
33 .gid_map = {
34 .nr_extents = 1,
35 .extent[0] = {
36 .first = 0,
37 .lower_first = 0,
38 .count = 4294967295U,
41 .kref = {
42 .refcount = ATOMIC_INIT(3),
44 .owner = GLOBAL_ROOT_UID,
45 .group = GLOBAL_ROOT_GID,
47 EXPORT_SYMBOL_GPL(init_user_ns);
50 * UID task count cache, to get fast user lookup in "alloc_uid"
51 * when changing user ID's (ie setuid() and friends).
54 #define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
55 #define UIDHASH_SZ (1 << UIDHASH_BITS)
56 #define UIDHASH_MASK (UIDHASH_SZ - 1)
57 #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
58 #define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid))))
60 static struct kmem_cache *uid_cachep;
61 struct hlist_head uidhash_table[UIDHASH_SZ];
64 * The uidhash_lock is mostly taken from process context, but it is
65 * occasionally also taken from softirq/tasklet context, when
66 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
67 * But free_uid() is also called with local interrupts disabled, and running
68 * local_bh_enable() with local interrupts disabled is an error - we'll run
69 * softirq callbacks, and they can unconditionally enable interrupts, and
70 * the caller of free_uid() didn't expect that..
72 static DEFINE_SPINLOCK(uidhash_lock);
74 /* root_user.__count is 1, for init task cred */
75 struct user_struct root_user = {
76 .__count = ATOMIC_INIT(1),
77 .processes = ATOMIC_INIT(1),
78 .files = ATOMIC_INIT(0),
79 .sigpending = ATOMIC_INIT(0),
80 .locked_shm = 0,
81 .uid = GLOBAL_ROOT_UID,
85 * These routines must be called with the uidhash spinlock held!
87 static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
89 hlist_add_head(&up->uidhash_node, hashent);
92 static void uid_hash_remove(struct user_struct *up)
94 hlist_del_init(&up->uidhash_node);
97 static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent)
99 struct user_struct *user;
100 struct hlist_node *h;
102 hlist_for_each_entry(user, h, hashent, uidhash_node) {
103 if (uid_eq(user->uid, uid)) {
104 atomic_inc(&user->__count);
105 return user;
109 return NULL;
112 /* IRQs are disabled and uidhash_lock is held upon function entry.
113 * IRQ state (as stored in flags) is restored and uidhash_lock released
114 * upon function exit.
116 static void free_user(struct user_struct *up, unsigned long flags)
117 __releases(&uidhash_lock)
119 uid_hash_remove(up);
120 spin_unlock_irqrestore(&uidhash_lock, flags);
121 key_put(up->uid_keyring);
122 key_put(up->session_keyring);
123 kmem_cache_free(uid_cachep, up);
127 * Locate the user_struct for the passed UID. If found, take a ref on it. The
128 * caller must undo that ref with free_uid().
130 * If the user_struct could not be found, return NULL.
132 struct user_struct *find_user(kuid_t uid)
134 struct user_struct *ret;
135 unsigned long flags;
137 spin_lock_irqsave(&uidhash_lock, flags);
138 ret = uid_hash_find(uid, uidhashentry(uid));
139 spin_unlock_irqrestore(&uidhash_lock, flags);
140 return ret;
143 void free_uid(struct user_struct *up)
145 unsigned long flags;
147 if (!up)
148 return;
150 local_irq_save(flags);
151 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
152 free_user(up, flags);
153 else
154 local_irq_restore(flags);
157 struct user_struct *alloc_uid(kuid_t uid)
159 struct hlist_head *hashent = uidhashentry(uid);
160 struct user_struct *up, *new;
162 spin_lock_irq(&uidhash_lock);
163 up = uid_hash_find(uid, hashent);
164 spin_unlock_irq(&uidhash_lock);
166 if (!up) {
167 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
168 if (!new)
169 goto out_unlock;
171 new->uid = uid;
172 atomic_set(&new->__count, 1);
175 * Before adding this, check whether we raced
176 * on adding the same user already..
178 spin_lock_irq(&uidhash_lock);
179 up = uid_hash_find(uid, hashent);
180 if (up) {
181 key_put(new->uid_keyring);
182 key_put(new->session_keyring);
183 kmem_cache_free(uid_cachep, new);
184 } else {
185 uid_hash_insert(new, hashent);
186 up = new;
188 spin_unlock_irq(&uidhash_lock);
191 return up;
193 out_unlock:
194 return NULL;
197 static int __init uid_cache_init(void)
199 int n;
201 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
202 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
204 for(n = 0; n < UIDHASH_SZ; ++n)
205 INIT_HLIST_HEAD(uidhash_table + n);
207 /* Insert the root user immediately (init already runs as root) */
208 spin_lock_irq(&uidhash_lock);
209 uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
210 spin_unlock_irq(&uidhash_lock);
212 return 0;
215 module_init(uid_cache_init);