Root/
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 | |
20 | /* |
21 | * userns count is 1 for root user, 1 for init_uts_ns, |
22 | * and 1 for... ? |
23 | */ |
24 | struct user_namespace init_user_ns = { |
25 | .uid_map = { |
26 | .nr_extents = 1, |
27 | .extent[0] = { |
28 | .first = 0, |
29 | .lower_first = 0, |
30 | .count = 4294967295U, |
31 | }, |
32 | }, |
33 | .gid_map = { |
34 | .nr_extents = 1, |
35 | .extent[0] = { |
36 | .first = 0, |
37 | .lower_first = 0, |
38 | .count = 4294967295U, |
39 | }, |
40 | }, |
41 | .kref = { |
42 | .refcount = ATOMIC_INIT(3), |
43 | }, |
44 | .owner = GLOBAL_ROOT_UID, |
45 | .group = GLOBAL_ROOT_GID, |
46 | }; |
47 | EXPORT_SYMBOL_GPL(init_user_ns); |
48 | |
49 | /* |
50 | * UID task count cache, to get fast user lookup in "alloc_uid" |
51 | * when changing user ID's (ie setuid() and friends). |
52 | */ |
53 | |
54 | #define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7) |
55 | #define UIDHASH_SZ (1 << UIDHASH_BITS) |
56 | #define UIDHASH_MASK (UIDHASH_SZ - 1) |
57 | #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK) |
58 | #define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid)))) |
59 | |
60 | static struct kmem_cache *uid_cachep; |
61 | struct hlist_head uidhash_table[UIDHASH_SZ]; |
62 | |
63 | /* |
64 | * The uidhash_lock is mostly taken from process context, but it is |
65 | * occasionally also taken from softirq/tasklet context, when |
66 | * task-structs get RCU-freed. Hence all locking must be softirq-safe. |
67 | * But free_uid() is also called with local interrupts disabled, and running |
68 | * local_bh_enable() with local interrupts disabled is an error - we'll run |
69 | * softirq callbacks, and they can unconditionally enable interrupts, and |
70 | * the caller of free_uid() didn't expect that.. |
71 | */ |
72 | static DEFINE_SPINLOCK(uidhash_lock); |
73 | |
74 | /* root_user.__count is 1, for init task cred */ |
75 | struct user_struct root_user = { |
76 | .__count = ATOMIC_INIT(1), |
77 | .processes = ATOMIC_INIT(1), |
78 | .files = ATOMIC_INIT(0), |
79 | .sigpending = ATOMIC_INIT(0), |
80 | .locked_shm = 0, |
81 | .uid = GLOBAL_ROOT_UID, |
82 | }; |
83 | |
84 | /* |
85 | * These routines must be called with the uidhash spinlock held! |
86 | */ |
87 | static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent) |
88 | { |
89 | hlist_add_head(&up->uidhash_node, hashent); |
90 | } |
91 | |
92 | static void uid_hash_remove(struct user_struct *up) |
93 | { |
94 | hlist_del_init(&up->uidhash_node); |
95 | } |
96 | |
97 | static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent) |
98 | { |
99 | struct user_struct *user; |
100 | struct hlist_node *h; |
101 | |
102 | hlist_for_each_entry(user, h, hashent, uidhash_node) { |
103 | if (uid_eq(user->uid, uid)) { |
104 | atomic_inc(&user->__count); |
105 | return user; |
106 | } |
107 | } |
108 | |
109 | return NULL; |
110 | } |
111 | |
112 | /* IRQs are disabled and uidhash_lock is held upon function entry. |
113 | * IRQ state (as stored in flags) is restored and uidhash_lock released |
114 | * upon function exit. |
115 | */ |
116 | static void free_user(struct user_struct *up, unsigned long flags) |
117 | __releases(&uidhash_lock) |
118 | { |
119 | uid_hash_remove(up); |
120 | spin_unlock_irqrestore(&uidhash_lock, flags); |
121 | key_put(up->uid_keyring); |
122 | key_put(up->session_keyring); |
123 | kmem_cache_free(uid_cachep, up); |
124 | } |
125 | |
126 | /* |
127 | * Locate the user_struct for the passed UID. If found, take a ref on it. The |
128 | * caller must undo that ref with free_uid(). |
129 | * |
130 | * If the user_struct could not be found, return NULL. |
131 | */ |
132 | struct user_struct *find_user(kuid_t uid) |
133 | { |
134 | struct user_struct *ret; |
135 | unsigned long flags; |
136 | |
137 | spin_lock_irqsave(&uidhash_lock, flags); |
138 | ret = uid_hash_find(uid, uidhashentry(uid)); |
139 | spin_unlock_irqrestore(&uidhash_lock, flags); |
140 | return ret; |
141 | } |
142 | |
143 | void free_uid(struct user_struct *up) |
144 | { |
145 | unsigned long flags; |
146 | |
147 | if (!up) |
148 | return; |
149 | |
150 | local_irq_save(flags); |
151 | if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) |
152 | free_user(up, flags); |
153 | else |
154 | local_irq_restore(flags); |
155 | } |
156 | |
157 | struct user_struct *alloc_uid(kuid_t uid) |
158 | { |
159 | struct hlist_head *hashent = uidhashentry(uid); |
160 | struct user_struct *up, *new; |
161 | |
162 | spin_lock_irq(&uidhash_lock); |
163 | up = uid_hash_find(uid, hashent); |
164 | spin_unlock_irq(&uidhash_lock); |
165 | |
166 | if (!up) { |
167 | new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL); |
168 | if (!new) |
169 | goto out_unlock; |
170 | |
171 | new->uid = uid; |
172 | atomic_set(&new->__count, 1); |
173 | |
174 | /* |
175 | * Before adding this, check whether we raced |
176 | * on adding the same user already.. |
177 | */ |
178 | spin_lock_irq(&uidhash_lock); |
179 | up = uid_hash_find(uid, hashent); |
180 | if (up) { |
181 | key_put(new->uid_keyring); |
182 | key_put(new->session_keyring); |
183 | kmem_cache_free(uid_cachep, new); |
184 | } else { |
185 | uid_hash_insert(new, hashent); |
186 | up = new; |
187 | } |
188 | spin_unlock_irq(&uidhash_lock); |
189 | } |
190 | |
191 | return up; |
192 | |
193 | out_unlock: |
194 | return NULL; |
195 | } |
196 | |
197 | static int __init uid_cache_init(void) |
198 | { |
199 | int n; |
200 | |
201 | uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct), |
202 | 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); |
203 | |
204 | for(n = 0; n < UIDHASH_SZ; ++n) |
205 | INIT_HLIST_HEAD(uidhash_table + n); |
206 | |
207 | /* Insert the root user immediately (init already runs as root) */ |
208 | spin_lock_irq(&uidhash_lock); |
209 | uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID)); |
210 | spin_unlock_irq(&uidhash_lock); |
211 | |
212 | return 0; |
213 | } |
214 | |
215 | module_init(uid_cache_init); |
216 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9