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1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
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 » Ingo Molnar
2006-01-25 [PATCH] fix uidhash_lock <-> RCU deadlock
16 #include <linux/interrupt.h>
9984de1a » Paul Gortmaker
2011-05-23 kernel: Map most files to use export.h instead of module.h
17 #include <linux/export.h>
acce292c » legoater
2007-07-15 user namespace: add the framework
18 #include <linux/user_namespace.h>
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
19
59607db3 » hallyn
2011-03-23 userns: add a user_namespace as creator/owner of uts_namespace
20 /*
21 * userns count is 1 for root user, 1 for init_uts_ns,
22 * and 1 for... ?
23 */
aee16ce7 » xemul
2008-02-08 namespaces: cleanup the code managed with the USER_NS option
24 struct user_namespace init_user_ns = {
25 .kref = {
59607db3 » hallyn
2011-03-23 userns: add a user_namespace as creator/owner of uts_namespace
26 .refcount = ATOMIC_INIT(3),
aee16ce7 » xemul
2008-02-08 namespaces: cleanup the code managed with the USER_NS option
27 },
18b6e041 » Serge Hallyn
2008-10-15 User namespaces: set of cleanups (v2)
28 .creator = &root_user,
aee16ce7 » xemul
2008-02-08 namespaces: cleanup the code managed with the USER_NS option
29 };
30 EXPORT_SYMBOL_GPL(init_user_ns);
31
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
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
37 #define UIDHASH_MASK (UIDHASH_SZ - 1)
38 #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
acce292c » legoater
2007-07-15 user namespace: add the framework
39 #define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid)))
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
40
e18b890b » Christoph Lameter
2006-12-06 [PATCH] slab: remove kmem_cache_t
41 static struct kmem_cache *uid_cachep;
4021cb27 » Ingo Molnar
2006-01-25 [PATCH] fix uidhash_lock <-> RCU deadlock
42
43 /*
44 * The uidhash_lock is mostly taken from process context, but it is
45 * occasionally also taken from softirq/tasklet context, when
46 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
47 * But free_uid() is also called with local interrupts disabled, and running
48 * local_bh_enable() with local interrupts disabled is an error - we'll run
49 * softirq callbacks, and they can unconditionally enable interrupts, and
50 * the caller of free_uid() didn't expect that..
4021cb27 » Ingo Molnar
2006-01-25 [PATCH] fix uidhash_lock <-> RCU deadlock
51 */
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
52 static DEFINE_SPINLOCK(uidhash_lock);
53
59607db3 » hallyn
2011-03-23 userns: add a user_namespace as creator/owner of uts_namespace
54 /* root_user.__count is 2, 1 for init task cred, 1 for init_user_ns->user_ns */
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
55 struct user_struct root_user = {
18b6e041 » Serge Hallyn
2008-10-15 User namespaces: set of cleanups (v2)
56 .__count = ATOMIC_INIT(2),
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
57 .processes = ATOMIC_INIT(1),
58 .files = ATOMIC_INIT(0),
59 .sigpending = ATOMIC_INIT(0),
60 .locked_shm = 0,
18b6e041 » Serge Hallyn
2008-10-15 User namespaces: set of cleanups (v2)
61 .user_ns = &init_user_ns,
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
62 };
63
5cb350ba » Dhaval Giani
2007-10-15 sched: group scheduling, sysfs tunables
64 /*
65 * These routines must be called with the uidhash spinlock held!
66 */
40aeb400 » Alexey Dobriyan
2007-10-16 user.c: deinline
67 static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
5cb350ba » Dhaval Giani
2007-10-15 sched: group scheduling, sysfs tunables
68 {
69 hlist_add_head(&up->uidhash_node, hashent);
70 }
71
40aeb400 » Alexey Dobriyan
2007-10-16 user.c: deinline
72 static void uid_hash_remove(struct user_struct *up)
5cb350ba » Dhaval Giani
2007-10-15 sched: group scheduling, sysfs tunables
73 {
74 hlist_del_init(&up->uidhash_node);
fb5ae64f » Serge E. Hallyn
2009-02-13 User namespaces: Only put the userns when we unhash the uid
75 put_user_ns(up->user_ns);
5cb350ba » Dhaval Giani
2007-10-15 sched: group scheduling, sysfs tunables
76 }
77
3959214f » kaysievers
2009-03-24 sched: delayed cleanup of user_struct
78 static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
79 {
80 struct user_struct *user;
81 struct hlist_node *h;
82
83 hlist_for_each_entry(user, h, hashent, uidhash_node) {
84 if (user->uid == uid) {
85 atomic_inc(&user->__count);
86 return user;
87 }
88 }
89
90 return NULL;
91 }
92
5cb350ba » Dhaval Giani
2007-10-15 sched: group scheduling, sysfs tunables
93 /* IRQs are disabled and uidhash_lock is held upon function entry.
94 * IRQ state (as stored in flags) is restored and uidhash_lock released
95 * upon function exit.
96 */
18b6e041 » Serge Hallyn
2008-10-15 User namespaces: set of cleanups (v2)
97 static void free_user(struct user_struct *up, unsigned long flags)
571428be » namhyung
2010-10-26 kernel/user.c: add lock release annotation on free_user()
98 __releases(&uidhash_lock)
5cb350ba » Dhaval Giani
2007-10-15 sched: group scheduling, sysfs tunables
99 {
100 uid_hash_remove(up);
101 spin_unlock_irqrestore(&uidhash_lock, flags);
102 key_put(up->uid_keyring);
103 key_put(up->session_keyring);
104 kmem_cache_free(uid_cachep, up);
105 }
106
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
107 /*
108 * Locate the user_struct for the passed UID. If found, take a ref on it. The
109 * caller must undo that ref with free_uid().
110 *
111 * If the user_struct could not be found, return NULL.
112 */
113 struct user_struct *find_user(uid_t uid)
114 {
115 struct user_struct *ret;
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
116 unsigned long flags;
6ded6ab9 » Serge Hallyn
2008-11-24 User namespaces: use the current_user_ns() macro
117 struct user_namespace *ns = current_user_ns();
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
118
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
119 spin_lock_irqsave(&uidhash_lock, flags);
acce292c » legoater
2007-07-15 user namespace: add the framework
120 ret = uid_hash_find(uid, uidhashentry(ns, uid));
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
121 spin_unlock_irqrestore(&uidhash_lock, flags);
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
122 return ret;
123 }
124
125 void free_uid(struct user_struct *up)
126 {
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
127 unsigned long flags;
128
36f57413 » Andrew Morton
2006-03-24 [PATCH] free_uid() locking improvement
129 if (!up)
130 return;
131
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
132 local_irq_save(flags);
5cb350ba » Dhaval Giani
2007-10-15 sched: group scheduling, sysfs tunables
133 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
134 free_user(up, flags);
135 else
36f57413 » Andrew Morton
2006-03-24 [PATCH] free_uid() locking improvement
136 local_irq_restore(flags);
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
137 }
138
354a1f4d » Andrew Morton
2008-04-30 alloc_uid: cleanup
139 struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid)
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
140 {
735de223 » xemul
2007-09-18 Convert uid hash to hlist
141 struct hlist_head *hashent = uidhashentry(ns, uid);
8eb703e4 » xemul
2008-01-25 uids: merge multiple error paths in alloc_uid() into one
142 struct user_struct *up, *new;
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
143
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
144 spin_lock_irq(&uidhash_lock);
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
145 up = uid_hash_find(uid, hashent);
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
146 spin_unlock_irq(&uidhash_lock);
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
147
148 if (!up) {
354a1f4d » Andrew Morton
2008-04-30 alloc_uid: cleanup
149 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
8eb703e4 » xemul
2008-01-25 uids: merge multiple error paths in alloc_uid() into one
150 if (!new)
151 goto out_unlock;
5e8869bb » xemul
2007-11-26 sched: don't forget to unlock uids_mutex on error paths
152
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
153 new->uid = uid;
154 atomic_set(&new->__count, 1);
155
18b6e041 » Serge Hallyn
2008-10-15 User namespaces: set of cleanups (v2)
156 new->user_ns = get_user_ns(ns);
157
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
158 /*
159 * Before adding this, check whether we raced
160 * on adding the same user already..
161 */
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
162 spin_lock_irq(&uidhash_lock);
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
163 up = uid_hash_find(uid, hashent);
164 if (up) {
4ef9e11d » Hillf Danton
2010-12-29 fix freeing user_struct in user cache
165 put_user_ns(ns);
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
166 key_put(new->uid_keyring);
167 key_put(new->session_keyring);
168 kmem_cache_free(uid_cachep, new);
169 } else {
170 uid_hash_insert(new, hashent);
171 up = new;
172 }
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
173 spin_unlock_irq(&uidhash_lock);
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
174 }
5cb350ba » Dhaval Giani
2007-10-15 sched: group scheduling, sysfs tunables
175
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
176 return up;
8eb703e4 » xemul
2008-01-25 uids: merge multiple error paths in alloc_uid() into one
177
178 out_unlock:
179 return NULL;
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
180 }
181
182 static int __init uid_cache_init(void)
183 {
184 int n;
185
186 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
20c2df83 » pmundt
2007-07-20 mm: Remove slab destructors from kmem_cache_create().
187 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
188
189 for(n = 0; n < UIDHASH_SZ; ++n)
735de223 » xemul
2007-09-18 Convert uid hash to hlist
190 INIT_HLIST_HEAD(init_user_ns.uidhash_table + n);
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
191
192 /* Insert the root user immediately (init already runs as root) */
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
193 spin_lock_irq(&uidhash_lock);
acce292c » legoater
2007-07-15 user namespace: add the framework
194 uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
3fa97c9d » Andrew Morton
2006-01-31 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
195 spin_unlock_irq(&uidhash_lock);
1da177e4 » Linus Torvalds
2005-04-16 Linux-2.6.12-rc2
196
197 return 0;
198 }
199
200 module_init(uid_cache_init);
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