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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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>
Ingo Molnar4021cb22006-01-25 15:23:07 +010016#include <linux/interrupt.h>
Paul Gortmaker9984de12011-05-23 14:51:41 -040017#include <linux/export.h>
Cedric Le Goateracce2922007-07-15 23:40:59 -070018#include <linux/user_namespace.h>
Eric W. Biederman98f842e2011-06-15 10:21:48 -070019#include <linux/proc_fs.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070020
Serge E. Hallyn59607db2011-03-23 16:43:16 -070021/*
22 * userns count is 1 for root user, 1 for init_uts_ns,
23 * and 1 for... ?
24 */
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080025struct user_namespace init_user_ns = {
Eric W. Biederman22d917d2011-11-17 00:11:58 -080026 .uid_map = {
27 .nr_extents = 1,
28 .extent[0] = {
29 .first = 0,
30 .lower_first = 0,
Eric W. Biederman4b06a812012-05-19 15:44:06 -060031 .count = 4294967295U,
Eric W. Biederman22d917d2011-11-17 00:11:58 -080032 },
33 },
34 .gid_map = {
35 .nr_extents = 1,
36 .extent[0] = {
37 .first = 0,
38 .lower_first = 0,
Eric W. Biederman4b06a812012-05-19 15:44:06 -060039 .count = 4294967295U,
Eric W. Biederman22d917d2011-11-17 00:11:58 -080040 },
41 },
Eric W. Biedermanf76d2072012-08-30 01:24:05 -070042 .projid_map = {
43 .nr_extents = 1,
44 .extent[0] = {
45 .first = 0,
46 .lower_first = 0,
47 .count = 4294967295U,
48 },
49 },
Eric W. Biedermanc61a2812012-12-28 18:58:39 -080050 .count = ATOMIC_INIT(3),
Eric W. Biederman783291e2011-11-17 01:32:59 -080051 .owner = GLOBAL_ROOT_UID,
52 .group = GLOBAL_ROOT_GID,
Eric W. Biederman98f842e2011-06-15 10:21:48 -070053 .proc_inum = PROC_USER_INIT_INO,
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080054};
55EXPORT_SYMBOL_GPL(init_user_ns);
56
Linus Torvalds1da177e2005-04-16 15:20:36 -070057/*
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
Eric W. Biederman7b44ab92011-11-16 23:20:58 -080062#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
63#define UIDHASH_SZ (1 << UIDHASH_BITS)
Linus Torvalds1da177e2005-04-16 15:20:36 -070064#define UIDHASH_MASK (UIDHASH_SZ - 1)
65#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
Eric W. Biederman7b44ab92011-11-16 23:20:58 -080066#define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid))))
Linus Torvalds1da177e2005-04-16 15:20:36 -070067
Christoph Lametere18b8902006-12-06 20:33:20 -080068static struct kmem_cache *uid_cachep;
Eric W. Biederman7b44ab92011-11-16 23:20:58 -080069struct hlist_head uidhash_table[UIDHASH_SZ];
Ingo Molnar4021cb22006-01-25 15:23:07 +010070
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.
Andrew Morton3fa97c92006-01-31 16:34:26 -080075 * 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..
Ingo Molnar4021cb22006-01-25 15:23:07 +010079 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070080static DEFINE_SPINLOCK(uidhash_lock);
81
Eric W. Biederman783291e2011-11-17 01:32:59 -080082/* root_user.__count is 1, for init task cred */
Linus Torvalds1da177e2005-04-16 15:20:36 -070083struct user_struct root_user = {
Eric W. Biederman783291e2011-11-17 01:32:59 -080084 .__count = ATOMIC_INIT(1),
Linus Torvalds1da177e2005-04-16 15:20:36 -070085 .processes = ATOMIC_INIT(1),
86 .files = ATOMIC_INIT(0),
87 .sigpending = ATOMIC_INIT(0),
Linus Torvalds1da177e2005-04-16 15:20:36 -070088 .locked_shm = 0,
Eric W. Biederman7b44ab92011-11-16 23:20:58 -080089 .uid = GLOBAL_ROOT_UID,
Linus Torvalds1da177e2005-04-16 15:20:36 -070090};
91
Dhaval Giani5cb350b2007-10-15 17:00:14 +020092/*
93 * These routines must be called with the uidhash spinlock held!
94 */
Alexey Dobriyan40aeb402007-10-16 23:30:09 -070095static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
Dhaval Giani5cb350b2007-10-15 17:00:14 +020096{
97 hlist_add_head(&up->uidhash_node, hashent);
98}
99
Alexey Dobriyan40aeb402007-10-16 23:30:09 -0700100static void uid_hash_remove(struct user_struct *up)
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200101{
102 hlist_del_init(&up->uidhash_node);
103}
104
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800105static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent)
Kay Sievers39592142009-03-24 15:43:30 +0100106{
107 struct user_struct *user;
Kay Sievers39592142009-03-24 15:43:30 +0100108
Sasha Levinb67bfe02013-02-27 17:06:00 -0800109 hlist_for_each_entry(user, hashent, uidhash_node) {
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800110 if (uid_eq(user->uid, uid)) {
Kay Sievers39592142009-03-24 15:43:30 +0100111 atomic_inc(&user->__count);
112 return user;
113 }
114 }
115
116 return NULL;
117}
118
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200119/* IRQs are disabled and uidhash_lock is held upon function entry.
120 * IRQ state (as stored in flags) is restored and uidhash_lock released
121 * upon function exit.
122 */
Serge Hallyn18b6e042008-10-15 16:38:45 -0500123static void free_user(struct user_struct *up, unsigned long flags)
Namhyung Kim571428b2010-10-26 14:22:43 -0700124 __releases(&uidhash_lock)
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200125{
126 uid_hash_remove(up);
127 spin_unlock_irqrestore(&uidhash_lock, flags);
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200128 key_put(up->uid_keyring);
129 key_put(up->session_keyring);
130 kmem_cache_free(uid_cachep, up);
131}
Srivatsa Vaddagiri24e377a2007-10-15 17:00:09 +0200132
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134 * Locate the user_struct for the passed UID. If found, take a ref on it. The
135 * caller must undo that ref with free_uid().
136 *
137 * If the user_struct could not be found, return NULL.
138 */
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800139struct user_struct *find_user(kuid_t uid)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140{
141 struct user_struct *ret;
Andrew Morton3fa97c92006-01-31 16:34:26 -0800142 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143
Andrew Morton3fa97c92006-01-31 16:34:26 -0800144 spin_lock_irqsave(&uidhash_lock, flags);
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800145 ret = uid_hash_find(uid, uidhashentry(uid));
Andrew Morton3fa97c92006-01-31 16:34:26 -0800146 spin_unlock_irqrestore(&uidhash_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147 return ret;
148}
149
150void free_uid(struct user_struct *up)
151{
Andrew Morton3fa97c92006-01-31 16:34:26 -0800152 unsigned long flags;
153
Andrew Morton36f57412006-03-24 03:15:47 -0800154 if (!up)
155 return;
156
Andrew Morton3fa97c92006-01-31 16:34:26 -0800157 local_irq_save(flags);
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200158 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
159 free_user(up, flags);
160 else
Andrew Morton36f57412006-03-24 03:15:47 -0800161 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162}
163
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800164struct user_struct *alloc_uid(kuid_t uid)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165{
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800166 struct hlist_head *hashent = uidhashentry(uid);
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100167 struct user_struct *up, *new;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168
Andrew Morton3fa97c92006-01-31 16:34:26 -0800169 spin_lock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 up = uid_hash_find(uid, hashent);
Andrew Morton3fa97c92006-01-31 16:34:26 -0800171 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172
173 if (!up) {
Andrew Morton354a1f42008-04-30 00:54:54 -0700174 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100175 if (!new)
176 goto out_unlock;
Pavel Emelyanov5e8869b2007-11-26 21:21:49 +0100177
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178 new->uid = uid;
179 atomic_set(&new->__count, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180
181 /*
182 * Before adding this, check whether we raced
183 * on adding the same user already..
184 */
Andrew Morton3fa97c92006-01-31 16:34:26 -0800185 spin_lock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186 up = uid_hash_find(uid, hashent);
187 if (up) {
188 key_put(new->uid_keyring);
189 key_put(new->session_keyring);
190 kmem_cache_free(uid_cachep, new);
191 } else {
192 uid_hash_insert(new, hashent);
193 up = new;
194 }
Andrew Morton3fa97c92006-01-31 16:34:26 -0800195 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196 }
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200197
Linus Torvalds1da177e2005-04-16 15:20:36 -0700198 return up;
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100199
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100200out_unlock:
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100201 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202}
203
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204static int __init uid_cache_init(void)
205{
206 int n;
207
208 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
Paul Mundt20c2df82007-07-20 10:11:58 +0900209 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210
211 for(n = 0; n < UIDHASH_SZ; ++n)
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800212 INIT_HLIST_HEAD(uidhash_table + n);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213
214 /* Insert the root user immediately (init already runs as root) */
Andrew Morton3fa97c92006-01-31 16:34:26 -0800215 spin_lock_irq(&uidhash_lock);
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800216 uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
Andrew Morton3fa97c92006-01-31 16:34:26 -0800217 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218
219 return 0;
220}
221
222module_init(uid_cache_init);