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