blob: 5c598ca781df4bf6f907043ed1d43f98b3b7ef58 [file] [log] [blame]
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>
Cedric Le Goateracce2922007-07-15 23:40:59 -070017#include <linux/module.h>
18#include <linux/user_namespace.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070019
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080020struct user_namespace init_user_ns = {
21 .kref = {
Serge E. Hallyn1d1e9752009-02-26 18:27:38 -060022 .refcount = ATOMIC_INIT(2),
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080023 },
Serge Hallyn18b6e042008-10-15 16:38:45 -050024 .creator = &root_user,
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080025};
26EXPORT_SYMBOL_GPL(init_user_ns);
27
Linus Torvalds1da177e2005-04-16 15:20:36 -070028/*
29 * UID task count cache, to get fast user lookup in "alloc_uid"
30 * when changing user ID's (ie setuid() and friends).
31 */
32
Linus Torvalds1da177e2005-04-16 15:20:36 -070033#define UIDHASH_MASK (UIDHASH_SZ - 1)
34#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
Cedric Le Goateracce2922007-07-15 23:40:59 -070035#define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid)))
Linus Torvalds1da177e2005-04-16 15:20:36 -070036
Christoph Lametere18b8902006-12-06 20:33:20 -080037static struct kmem_cache *uid_cachep;
Ingo Molnar4021cb22006-01-25 15:23:07 +010038
39/*
40 * The uidhash_lock is mostly taken from process context, but it is
41 * occasionally also taken from softirq/tasklet context, when
42 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
Andrew Morton3fa97c92006-01-31 16:34:26 -080043 * But free_uid() is also called with local interrupts disabled, and running
44 * local_bh_enable() with local interrupts disabled is an error - we'll run
45 * softirq callbacks, and they can unconditionally enable interrupts, and
46 * the caller of free_uid() didn't expect that..
Ingo Molnar4021cb22006-01-25 15:23:07 +010047 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070048static DEFINE_SPINLOCK(uidhash_lock);
49
Serge Hallyn18b6e042008-10-15 16:38:45 -050050/* root_user.__count is 2, 1 for init task cred, 1 for init_user_ns->creator */
Linus Torvalds1da177e2005-04-16 15:20:36 -070051struct user_struct root_user = {
Serge Hallyn18b6e042008-10-15 16:38:45 -050052 .__count = ATOMIC_INIT(2),
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 .processes = ATOMIC_INIT(1),
54 .files = ATOMIC_INIT(0),
55 .sigpending = ATOMIC_INIT(0),
Linus Torvalds1da177e2005-04-16 15:20:36 -070056 .locked_shm = 0,
Serge Hallyn18b6e042008-10-15 16:38:45 -050057 .user_ns = &init_user_ns,
Linus Torvalds1da177e2005-04-16 15:20:36 -070058};
59
Dhaval Giani5cb350b2007-10-15 17:00:14 +020060/*
61 * These routines must be called with the uidhash spinlock held!
62 */
Alexey Dobriyan40aeb402007-10-16 23:30:09 -070063static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
Dhaval Giani5cb350b2007-10-15 17:00:14 +020064{
65 hlist_add_head(&up->uidhash_node, hashent);
66}
67
Alexey Dobriyan40aeb402007-10-16 23:30:09 -070068static void uid_hash_remove(struct user_struct *up)
Dhaval Giani5cb350b2007-10-15 17:00:14 +020069{
70 hlist_del_init(&up->uidhash_node);
Serge E. Hallynfb5ae642009-02-13 14:04:21 +000071 put_user_ns(up->user_ns);
Dhaval Giani5cb350b2007-10-15 17:00:14 +020072}
73
Kay Sievers39592142009-03-24 15:43:30 +010074static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
75{
76 struct user_struct *user;
77 struct hlist_node *h;
78
79 hlist_for_each_entry(user, h, hashent, uidhash_node) {
80 if (user->uid == uid) {
81 atomic_inc(&user->__count);
82 return user;
83 }
84 }
85
86 return NULL;
87}
88
Dhaval Giani5cb350b2007-10-15 17:00:14 +020089/* IRQs are disabled and uidhash_lock is held upon function entry.
90 * IRQ state (as stored in flags) is restored and uidhash_lock released
91 * upon function exit.
92 */
Serge Hallyn18b6e042008-10-15 16:38:45 -050093static void free_user(struct user_struct *up, unsigned long flags)
Namhyung Kim571428b2010-10-26 14:22:43 -070094 __releases(&uidhash_lock)
Dhaval Giani5cb350b2007-10-15 17:00:14 +020095{
96 uid_hash_remove(up);
97 spin_unlock_irqrestore(&uidhash_lock, flags);
Dhaval Giani5cb350b2007-10-15 17:00:14 +020098 key_put(up->uid_keyring);
99 key_put(up->session_keyring);
100 kmem_cache_free(uid_cachep, up);
101}
Srivatsa Vaddagiri24e377a2007-10-15 17:00:09 +0200102
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 * Locate the user_struct for the passed UID. If found, take a ref on it. The
105 * caller must undo that ref with free_uid().
106 *
107 * If the user_struct could not be found, return NULL.
108 */
109struct user_struct *find_user(uid_t uid)
110{
111 struct user_struct *ret;
Andrew Morton3fa97c92006-01-31 16:34:26 -0800112 unsigned long flags;
Serge Hallyn6ded6ab2008-11-24 16:24:10 -0500113 struct user_namespace *ns = current_user_ns();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114
Andrew Morton3fa97c92006-01-31 16:34:26 -0800115 spin_lock_irqsave(&uidhash_lock, flags);
Cedric Le Goateracce2922007-07-15 23:40:59 -0700116 ret = uid_hash_find(uid, uidhashentry(ns, uid));
Andrew Morton3fa97c92006-01-31 16:34:26 -0800117 spin_unlock_irqrestore(&uidhash_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118 return ret;
119}
120
121void free_uid(struct user_struct *up)
122{
Andrew Morton3fa97c92006-01-31 16:34:26 -0800123 unsigned long flags;
124
Andrew Morton36f57412006-03-24 03:15:47 -0800125 if (!up)
126 return;
127
Andrew Morton3fa97c92006-01-31 16:34:26 -0800128 local_irq_save(flags);
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200129 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
130 free_user(up, flags);
131 else
Andrew Morton36f57412006-03-24 03:15:47 -0800132 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133}
134
Andrew Morton354a1f42008-04-30 00:54:54 -0700135struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136{
Pavel Emelyanov735de222007-09-18 22:46:44 -0700137 struct hlist_head *hashent = uidhashentry(ns, uid);
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100138 struct user_struct *up, *new;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700139
Andrew Morton3fa97c92006-01-31 16:34:26 -0800140 spin_lock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141 up = uid_hash_find(uid, hashent);
Andrew Morton3fa97c92006-01-31 16:34:26 -0800142 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143
144 if (!up) {
Andrew Morton354a1f42008-04-30 00:54:54 -0700145 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100146 if (!new)
147 goto out_unlock;
Pavel Emelyanov5e8869b2007-11-26 21:21:49 +0100148
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149 new->uid = uid;
150 atomic_set(&new->__count, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151
Serge Hallyn18b6e042008-10-15 16:38:45 -0500152 new->user_ns = get_user_ns(ns);
153
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154 /*
155 * Before adding this, check whether we raced
156 * on adding the same user already..
157 */
Andrew Morton3fa97c92006-01-31 16:34:26 -0800158 spin_lock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 up = uid_hash_find(uid, hashent);
160 if (up) {
Hillf Danton4ef9e112010-12-29 21:55:28 +0800161 put_user_ns(ns);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162 key_put(new->uid_keyring);
163 key_put(new->session_keyring);
164 kmem_cache_free(uid_cachep, new);
165 } else {
166 uid_hash_insert(new, hashent);
167 up = new;
168 }
Andrew Morton3fa97c92006-01-31 16:34:26 -0800169 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 }
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200171
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 return up;
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100173
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100174out_unlock:
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100175 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176}
177
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178static int __init uid_cache_init(void)
179{
180 int n;
181
182 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
Paul Mundt20c2df82007-07-20 10:11:58 +0900183 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700184
185 for(n = 0; n < UIDHASH_SZ; ++n)
Pavel Emelyanov735de222007-09-18 22:46:44 -0700186 INIT_HLIST_HEAD(init_user_ns.uidhash_table + n);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700187
188 /* Insert the root user immediately (init already runs as root) */
Andrew Morton3fa97c92006-01-31 16:34:26 -0800189 spin_lock_irq(&uidhash_lock);
Cedric Le Goateracce2922007-07-15 23:40:59 -0700190 uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
Andrew Morton3fa97c92006-01-31 16:34:26 -0800191 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192
193 return 0;
194}
195
196module_init(uid_cache_init);