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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#include <linux/proc_ns.h>
20
21/*
22 * userns count is 1 for root user, 1 for init_uts_ns,
23 * and 1 for... ?
24 */
25struct user_namespace init_user_ns = {
26 .uid_map = {
27 .nr_extents = 1,
28 .extent[0] = {
29 .first = 0,
30 .lower_first = 0,
31 .count = 4294967295U,
32 },
33 },
34 .gid_map = {
35 .nr_extents = 1,
36 .extent[0] = {
37 .first = 0,
38 .lower_first = 0,
39 .count = 4294967295U,
40 },
41 },
42 .projid_map = {
43 .nr_extents = 1,
44 .extent[0] = {
45 .first = 0,
46 .lower_first = 0,
47 .count = 4294967295U,
48 },
49 },
50 .count = ATOMIC_INIT(3),
51 .owner = GLOBAL_ROOT_UID,
52 .group = GLOBAL_ROOT_GID,
53 .ns.inum = PROC_USER_INIT_INO,
54#ifdef CONFIG_USER_NS
55 .ns.ops = &userns_operations,
56#endif
57 .flags = USERNS_INIT_FLAGS,
58#ifdef CONFIG_PERSISTENT_KEYRINGS
59 .persistent_keyring_register_sem =
60 __RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),
61#endif
62};
63EXPORT_SYMBOL_GPL(init_user_ns);
64
65/*
66 * UID task count cache, to get fast user lookup in "alloc_uid"
67 * when changing user ID's (ie setuid() and friends).
68 */
69
70#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
71#define UIDHASH_SZ (1 << UIDHASH_BITS)
72#define UIDHASH_MASK (UIDHASH_SZ - 1)
73#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
74#define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid))))
75
76static struct kmem_cache *uid_cachep;
77struct hlist_head uidhash_table[UIDHASH_SZ];
78
79/*
80 * The uidhash_lock is mostly taken from process context, but it is
81 * occasionally also taken from softirq/tasklet context, when
82 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
83 * But free_uid() is also called with local interrupts disabled, and running
84 * local_bh_enable() with local interrupts disabled is an error - we'll run
85 * softirq callbacks, and they can unconditionally enable interrupts, and
86 * the caller of free_uid() didn't expect that..
87 */
88static DEFINE_SPINLOCK(uidhash_lock);
89
90/* root_user.__count is 1, for init task cred */
91struct user_struct root_user = {
92 .__count = ATOMIC_INIT(1),
93 .processes = ATOMIC_INIT(1),
94 .sigpending = ATOMIC_INIT(0),
95 .locked_shm = 0,
96 .uid = GLOBAL_ROOT_UID,
97};
98
99/*
100 * These routines must be called with the uidhash spinlock held!
101 */
102static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
103{
104 hlist_add_head(&up->uidhash_node, hashent);
105}
106
107static void uid_hash_remove(struct user_struct *up)
108{
109 hlist_del_init(&up->uidhash_node);
110}
111
112static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent)
113{
114 struct user_struct *user;
115
116 hlist_for_each_entry(user, hashent, uidhash_node) {
117 if (uid_eq(user->uid, uid)) {
118 atomic_inc(&user->__count);
119 return user;
120 }
121 }
122
123 return NULL;
124}
125
126/* IRQs are disabled and uidhash_lock is held upon function entry.
127 * IRQ state (as stored in flags) is restored and uidhash_lock released
128 * upon function exit.
129 */
130static void free_user(struct user_struct *up, unsigned long flags)
131 __releases(&uidhash_lock)
132{
133 uid_hash_remove(up);
134 spin_unlock_irqrestore(&uidhash_lock, flags);
135 key_put(up->uid_keyring);
136 key_put(up->session_keyring);
137 kmem_cache_free(uid_cachep, up);
138}
139
140/*
141 * Locate the user_struct for the passed UID. If found, take a ref on it. The
142 * caller must undo that ref with free_uid().
143 *
144 * If the user_struct could not be found, return NULL.
145 */
146struct user_struct *find_user(kuid_t uid)
147{
148 struct user_struct *ret;
149 unsigned long flags;
150
151 spin_lock_irqsave(&uidhash_lock, flags);
152 ret = uid_hash_find(uid, uidhashentry(uid));
153 spin_unlock_irqrestore(&uidhash_lock, flags);
154 return ret;
155}
156
157void free_uid(struct user_struct *up)
158{
159 unsigned long flags;
160
161 if (!up)
162 return;
163
164 local_irq_save(flags);
165 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
166 free_user(up, flags);
167 else
168 local_irq_restore(flags);
169}
170
171struct user_struct *alloc_uid(kuid_t uid)
172{
173 struct hlist_head *hashent = uidhashentry(uid);
174 struct user_struct *up, *new;
175
176 spin_lock_irq(&uidhash_lock);
177 up = uid_hash_find(uid, hashent);
178 spin_unlock_irq(&uidhash_lock);
179
180 if (!up) {
181 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
182 if (!new)
183 goto out_unlock;
184
185 new->uid = uid;
186 atomic_set(&new->__count, 1);
187
188 /*
189 * Before adding this, check whether we raced
190 * on adding the same user already..
191 */
192 spin_lock_irq(&uidhash_lock);
193 up = uid_hash_find(uid, hashent);
194 if (up) {
195 key_put(new->uid_keyring);
196 key_put(new->session_keyring);
197 kmem_cache_free(uid_cachep, new);
198 } else {
199 uid_hash_insert(new, hashent);
200 up = new;
201 }
202 spin_unlock_irq(&uidhash_lock);
203 }
204
205 return up;
206
207out_unlock:
208 return NULL;
209}
210
211static int __init uid_cache_init(void)
212{
213 int n;
214
215 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
216 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
217
218 for(n = 0; n < UIDHASH_SZ; ++n)
219 INIT_HLIST_HEAD(uidhash_table + n);
220
221 /* Insert the root user immediately (init already runs as root) */
222 spin_lock_irq(&uidhash_lock);
223 uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
224 spin_unlock_irq(&uidhash_lock);
225
226 return 0;
227}
228subsys_initcall(uid_cache_init);
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#include <linux/proc_ns.h>
20
21/*
22 * userns count is 1 for root user, 1 for init_uts_ns,
23 * and 1 for... ?
24 */
25struct user_namespace init_user_ns = {
26 .uid_map = {
27 .nr_extents = 1,
28 .extent[0] = {
29 .first = 0,
30 .lower_first = 0,
31 .count = 4294967295U,
32 },
33 },
34 .gid_map = {
35 .nr_extents = 1,
36 .extent[0] = {
37 .first = 0,
38 .lower_first = 0,
39 .count = 4294967295U,
40 },
41 },
42 .projid_map = {
43 .nr_extents = 1,
44 .extent[0] = {
45 .first = 0,
46 .lower_first = 0,
47 .count = 4294967295U,
48 },
49 },
50 .count = ATOMIC_INIT(3),
51 .owner = GLOBAL_ROOT_UID,
52 .group = GLOBAL_ROOT_GID,
53 .proc_inum = PROC_USER_INIT_INO,
54#ifdef CONFIG_PERSISTENT_KEYRINGS
55 .persistent_keyring_register_sem =
56 __RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),
57#endif
58};
59EXPORT_SYMBOL_GPL(init_user_ns);
60
61/*
62 * UID task count cache, to get fast user lookup in "alloc_uid"
63 * when changing user ID's (ie setuid() and friends).
64 */
65
66#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
67#define UIDHASH_SZ (1 << UIDHASH_BITS)
68#define UIDHASH_MASK (UIDHASH_SZ - 1)
69#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
70#define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid))))
71
72static struct kmem_cache *uid_cachep;
73struct hlist_head uidhash_table[UIDHASH_SZ];
74
75/*
76 * The uidhash_lock is mostly taken from process context, but it is
77 * occasionally also taken from softirq/tasklet context, when
78 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
79 * But free_uid() is also called with local interrupts disabled, and running
80 * local_bh_enable() with local interrupts disabled is an error - we'll run
81 * softirq callbacks, and they can unconditionally enable interrupts, and
82 * the caller of free_uid() didn't expect that..
83 */
84static DEFINE_SPINLOCK(uidhash_lock);
85
86/* root_user.__count is 1, for init task cred */
87struct user_struct root_user = {
88 .__count = ATOMIC_INIT(1),
89 .processes = ATOMIC_INIT(1),
90 .files = ATOMIC_INIT(0),
91 .sigpending = ATOMIC_INIT(0),
92 .locked_shm = 0,
93 .uid = GLOBAL_ROOT_UID,
94};
95
96/*
97 * These routines must be called with the uidhash spinlock held!
98 */
99static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
100{
101 hlist_add_head(&up->uidhash_node, hashent);
102}
103
104static void uid_hash_remove(struct user_struct *up)
105{
106 hlist_del_init(&up->uidhash_node);
107}
108
109static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent)
110{
111 struct user_struct *user;
112
113 hlist_for_each_entry(user, hashent, uidhash_node) {
114 if (uid_eq(user->uid, uid)) {
115 atomic_inc(&user->__count);
116 return user;
117 }
118 }
119
120 return NULL;
121}
122
123/* IRQs are disabled and uidhash_lock is held upon function entry.
124 * IRQ state (as stored in flags) is restored and uidhash_lock released
125 * upon function exit.
126 */
127static void free_user(struct user_struct *up, unsigned long flags)
128 __releases(&uidhash_lock)
129{
130 uid_hash_remove(up);
131 spin_unlock_irqrestore(&uidhash_lock, flags);
132 key_put(up->uid_keyring);
133 key_put(up->session_keyring);
134 kmem_cache_free(uid_cachep, up);
135}
136
137/*
138 * Locate the user_struct for the passed UID. If found, take a ref on it. The
139 * caller must undo that ref with free_uid().
140 *
141 * If the user_struct could not be found, return NULL.
142 */
143struct user_struct *find_user(kuid_t uid)
144{
145 struct user_struct *ret;
146 unsigned long flags;
147
148 spin_lock_irqsave(&uidhash_lock, flags);
149 ret = uid_hash_find(uid, uidhashentry(uid));
150 spin_unlock_irqrestore(&uidhash_lock, flags);
151 return ret;
152}
153
154void free_uid(struct user_struct *up)
155{
156 unsigned long flags;
157
158 if (!up)
159 return;
160
161 local_irq_save(flags);
162 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
163 free_user(up, flags);
164 else
165 local_irq_restore(flags);
166}
167
168struct user_struct *alloc_uid(kuid_t uid)
169{
170 struct hlist_head *hashent = uidhashentry(uid);
171 struct user_struct *up, *new;
172
173 spin_lock_irq(&uidhash_lock);
174 up = uid_hash_find(uid, hashent);
175 spin_unlock_irq(&uidhash_lock);
176
177 if (!up) {
178 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
179 if (!new)
180 goto out_unlock;
181
182 new->uid = uid;
183 atomic_set(&new->__count, 1);
184
185 /*
186 * Before adding this, check whether we raced
187 * on adding the same user already..
188 */
189 spin_lock_irq(&uidhash_lock);
190 up = uid_hash_find(uid, hashent);
191 if (up) {
192 key_put(new->uid_keyring);
193 key_put(new->session_keyring);
194 kmem_cache_free(uid_cachep, new);
195 } else {
196 uid_hash_insert(new, hashent);
197 up = new;
198 }
199 spin_unlock_irq(&uidhash_lock);
200 }
201
202 return up;
203
204out_unlock:
205 return NULL;
206}
207
208static int __init uid_cache_init(void)
209{
210 int n;
211
212 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
213 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
214
215 for(n = 0; n < UIDHASH_SZ; ++n)
216 INIT_HLIST_HEAD(uidhash_table + n);
217
218 /* Insert the root user immediately (init already runs as root) */
219 spin_lock_irq(&uidhash_lock);
220 uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
221 spin_unlock_irq(&uidhash_lock);
222
223 return 0;
224}
225subsys_initcall(uid_cache_init);