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1da177e Linux-2.6.12-rc2
Linus Torvalds authored
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>
4021cb2 [PATCH] fix uidhash_lock <-> RCU deadlock
Ingo Molnar authored
16 #include <linux/interrupt.h>
9984de1 kernel: Map most files to use export.h instead of module.h
Paul Gortmaker authored
17 #include <linux/export.h>
acce292 @legoater user namespace: add the framework
legoater authored
18 #include <linux/user_namespace.h>
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
19
59607db @hallyn userns: add a user_namespace as creator/owner of uts_namespace
hallyn authored
20 /*
21 * userns count is 1 for root user, 1 for init_uts_ns,
22 * and 1 for... ?
23 */
aee16ce @xemul namespaces: cleanup the code managed with the USER_NS option
xemul authored
24 struct user_namespace init_user_ns = {
22d917d @ebiederm userns: Rework the user_namespace adding uid/gid mapping support
ebiederm authored
25 .uid_map = {
26 .nr_extents = 1,
27 .extent[0] = {
28 .first = 0,
29 .lower_first = 0,
4b06a81 @ebiederm userns: Silence silly gcc warning.
ebiederm authored
30 .count = 4294967295U,
22d917d @ebiederm userns: Rework the user_namespace adding uid/gid mapping support
ebiederm authored
31 },
32 },
33 .gid_map = {
34 .nr_extents = 1,
35 .extent[0] = {
36 .first = 0,
37 .lower_first = 0,
4b06a81 @ebiederm userns: Silence silly gcc warning.
ebiederm authored
38 .count = 4294967295U,
22d917d @ebiederm userns: Rework the user_namespace adding uid/gid mapping support
ebiederm authored
39 },
40 },
f76d207 @ebiederm userns: Add kprojid_t and associated infrastructure in projid.h
ebiederm authored
41 .projid_map = {
42 .nr_extents = 1,
43 .extent[0] = {
44 .first = 0,
45 .lower_first = 0,
46 .count = 4294967295U,
47 },
48 },
aee16ce @xemul namespaces: cleanup the code managed with the USER_NS option
xemul authored
49 .kref = {
59607db @hallyn userns: add a user_namespace as creator/owner of uts_namespace
hallyn authored
50 .refcount = ATOMIC_INIT(3),
aee16ce @xemul namespaces: cleanup the code managed with the USER_NS option
xemul authored
51 },
783291e @ebiederm userns: Simplify the user_namespace by making userns->creator a kuid.
ebiederm authored
52 .owner = GLOBAL_ROOT_UID,
53 .group = GLOBAL_ROOT_GID,
aee16ce @xemul namespaces: cleanup the code managed with the USER_NS option
xemul authored
54 };
55 EXPORT_SYMBOL_GPL(init_user_ns);
56
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
57 /*
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
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
62 #define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
63 #define UIDHASH_SZ (1 << UIDHASH_BITS)
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
64 #define UIDHASH_MASK (UIDHASH_SZ - 1)
65 #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
66 #define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid))))
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
67
e18b890 [PATCH] slab: remove kmem_cache_t
Christoph Lameter authored
68 static struct kmem_cache *uid_cachep;
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
69 struct hlist_head uidhash_table[UIDHASH_SZ];
4021cb2 [PATCH] fix uidhash_lock <-> RCU deadlock
Ingo Molnar authored
70
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.
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
75 * 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..
4021cb2 [PATCH] fix uidhash_lock <-> RCU deadlock
Ingo Molnar authored
79 */
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
80 static DEFINE_SPINLOCK(uidhash_lock);
81
783291e @ebiederm userns: Simplify the user_namespace by making userns->creator a kuid.
ebiederm authored
82 /* root_user.__count is 1, for init task cred */
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
83 struct user_struct root_user = {
783291e @ebiederm userns: Simplify the user_namespace by making userns->creator a kuid.
ebiederm authored
84 .__count = ATOMIC_INIT(1),
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
85 .processes = ATOMIC_INIT(1),
86 .files = ATOMIC_INIT(0),
87 .sigpending = ATOMIC_INIT(0),
88 .locked_shm = 0,
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
89 .uid = GLOBAL_ROOT_UID,
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
90 };
91
5cb350b sched: group scheduling, sysfs tunables
Dhaval Giani authored
92 /*
93 * These routines must be called with the uidhash spinlock held!
94 */
40aeb40 user.c: deinline
Alexey Dobriyan authored
95 static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
5cb350b sched: group scheduling, sysfs tunables
Dhaval Giani authored
96 {
97 hlist_add_head(&up->uidhash_node, hashent);
98 }
99
40aeb40 user.c: deinline
Alexey Dobriyan authored
100 static void uid_hash_remove(struct user_struct *up)
5cb350b sched: group scheduling, sysfs tunables
Dhaval Giani authored
101 {
102 hlist_del_init(&up->uidhash_node);
103 }
104
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
105 static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent)
3959214 @kaysievers sched: delayed cleanup of user_struct
kaysievers authored
106 {
107 struct user_struct *user;
108 struct hlist_node *h;
109
110 hlist_for_each_entry(user, h, hashent, uidhash_node) {
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
111 if (uid_eq(user->uid, uid)) {
3959214 @kaysievers sched: delayed cleanup of user_struct
kaysievers authored
112 atomic_inc(&user->__count);
113 return user;
114 }
115 }
116
117 return NULL;
118 }
119
5cb350b sched: group scheduling, sysfs tunables
Dhaval Giani authored
120 /* IRQs are disabled and uidhash_lock is held upon function entry.
121 * IRQ state (as stored in flags) is restored and uidhash_lock released
122 * upon function exit.
123 */
18b6e04 User namespaces: set of cleanups (v2)
Serge Hallyn authored
124 static void free_user(struct user_struct *up, unsigned long flags)
571428b @namhyung kernel/user.c: add lock release annotation on free_user()
namhyung authored
125 __releases(&uidhash_lock)
5cb350b sched: group scheduling, sysfs tunables
Dhaval Giani authored
126 {
127 uid_hash_remove(up);
128 spin_unlock_irqrestore(&uidhash_lock, flags);
129 key_put(up->uid_keyring);
130 key_put(up->session_keyring);
131 kmem_cache_free(uid_cachep, up);
132 }
133
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
134 /*
135 * Locate the user_struct for the passed UID. If found, take a ref on it. The
136 * caller must undo that ref with free_uid().
137 *
138 * If the user_struct could not be found, return NULL.
139 */
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
140 struct user_struct *find_user(kuid_t uid)
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
141 {
142 struct user_struct *ret;
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
143 unsigned long flags;
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
144
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
145 spin_lock_irqsave(&uidhash_lock, flags);
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
146 ret = uid_hash_find(uid, uidhashentry(uid));
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
147 spin_unlock_irqrestore(&uidhash_lock, flags);
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
148 return ret;
149 }
150
151 void free_uid(struct user_struct *up)
152 {
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
153 unsigned long flags;
154
36f5741 [PATCH] free_uid() locking improvement
Andrew Morton authored
155 if (!up)
156 return;
157
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
158 local_irq_save(flags);
5cb350b sched: group scheduling, sysfs tunables
Dhaval Giani authored
159 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
160 free_user(up, flags);
161 else
36f5741 [PATCH] free_uid() locking improvement
Andrew Morton authored
162 local_irq_restore(flags);
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
163 }
164
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
165 struct user_struct *alloc_uid(kuid_t uid)
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
166 {
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
167 struct hlist_head *hashent = uidhashentry(uid);
8eb703e @xemul uids: merge multiple error paths in alloc_uid() into one
xemul authored
168 struct user_struct *up, *new;
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
169
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
170 spin_lock_irq(&uidhash_lock);
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
171 up = uid_hash_find(uid, hashent);
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
172 spin_unlock_irq(&uidhash_lock);
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
173
174 if (!up) {
354a1f4 alloc_uid: cleanup
Andrew Morton authored
175 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
8eb703e @xemul uids: merge multiple error paths in alloc_uid() into one
xemul authored
176 if (!new)
177 goto out_unlock;
5e8869b @xemul sched: don't forget to unlock uids_mutex on error paths
xemul authored
178
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
179 new->uid = uid;
180 atomic_set(&new->__count, 1);
181
182 /*
183 * Before adding this, check whether we raced
184 * on adding the same user already..
185 */
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
186 spin_lock_irq(&uidhash_lock);
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
187 up = uid_hash_find(uid, hashent);
188 if (up) {
189 key_put(new->uid_keyring);
190 key_put(new->session_keyring);
191 kmem_cache_free(uid_cachep, new);
192 } else {
193 uid_hash_insert(new, hashent);
194 up = new;
195 }
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
196 spin_unlock_irq(&uidhash_lock);
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
197 }
5cb350b sched: group scheduling, sysfs tunables
Dhaval Giani authored
198
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
199 return up;
8eb703e @xemul uids: merge multiple error paths in alloc_uid() into one
xemul authored
200
201 out_unlock:
202 return NULL;
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
203 }
204
205 static int __init uid_cache_init(void)
206 {
207 int n;
208
209 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
20c2df8 @pmundt mm: Remove slab destructors from kmem_cache_create().
pmundt authored
210 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
211
212 for(n = 0; n < UIDHASH_SZ; ++n)
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
213 INIT_HLIST_HEAD(uidhash_table + n);
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
214
215 /* Insert the root user immediately (init already runs as root) */
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
216 spin_lock_irq(&uidhash_lock);
7b44ab9 @ebiederm userns: Disassociate user_struct from the user_namespace.
ebiederm authored
217 uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
3fa97c9 [PATCH] "Fix uidhash_lock <-> RXU deadlock" fix
Andrew Morton authored
218 spin_unlock_irq(&uidhash_lock);
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
219
220 return 0;
221 }
222
223 module_init(uid_cache_init);
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