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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// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * The "user cache".
4 *
5 * (C) Copyright 1991-2000 Linus Torvalds
6 *
7 * We have a per-user structure to keep track of how many
8 * processes, files etc the user has claimed, in order to be
9 * able to have per-user limits for system resources.
10 */
11
12#include <linux/init.h>
13#include <linux/sched.h>
14#include <linux/slab.h>
15#include <linux/bitops.h>
16#include <linux/key.h>
17#include <linux/sched/user.h>
18#include <linux/interrupt.h>
19#include <linux/export.h>
20#include <linux/user_namespace.h>
21#include <linux/binfmts.h>
22#include <linux/proc_ns.h>
23
24#if IS_ENABLED(CONFIG_BINFMT_MISC)
25struct binfmt_misc init_binfmt_misc = {
26 .entries = LIST_HEAD_INIT(init_binfmt_misc.entries),
27 .enabled = true,
28 .entries_lock = __RW_LOCK_UNLOCKED(init_binfmt_misc.entries_lock),
29};
30EXPORT_SYMBOL_GPL(init_binfmt_misc);
31#endif
32
33/*
34 * userns count is 1 for root user, 1 for init_uts_ns,
35 * and 1 for... ?
36 */
37struct user_namespace init_user_ns = {
38 .uid_map = {
39 .nr_extents = 1,
40 {
41 .extent[0] = {
42 .first = 0,
43 .lower_first = 0,
44 .count = 4294967295U,
45 },
46 },
47 },
48 .gid_map = {
49 .nr_extents = 1,
50 {
51 .extent[0] = {
52 .first = 0,
53 .lower_first = 0,
54 .count = 4294967295U,
55 },
56 },
57 },
58 .projid_map = {
59 .nr_extents = 1,
60 {
61 .extent[0] = {
62 .first = 0,
63 .lower_first = 0,
64 .count = 4294967295U,
65 },
66 },
67 },
68 .ns.count = REFCOUNT_INIT(3),
69 .owner = GLOBAL_ROOT_UID,
70 .group = GLOBAL_ROOT_GID,
71 .ns.inum = PROC_USER_INIT_INO,
72#ifdef CONFIG_USER_NS
73 .ns.ops = &userns_operations,
74#endif
75 .flags = USERNS_INIT_FLAGS,
76#ifdef CONFIG_KEYS
77 .keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list),
78 .keyring_sem = __RWSEM_INITIALIZER(init_user_ns.keyring_sem),
79#endif
80#if IS_ENABLED(CONFIG_BINFMT_MISC)
81 .binfmt_misc = &init_binfmt_misc,
82#endif
83};
84EXPORT_SYMBOL_GPL(init_user_ns);
85
86/*
87 * UID task count cache, to get fast user lookup in "alloc_uid"
88 * when changing user ID's (ie setuid() and friends).
89 */
90
91#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
92#define UIDHASH_SZ (1 << UIDHASH_BITS)
93#define UIDHASH_MASK (UIDHASH_SZ - 1)
94#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
95#define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid))))
96
97static struct kmem_cache *uid_cachep;
98static struct hlist_head uidhash_table[UIDHASH_SZ];
99
100/*
101 * The uidhash_lock is mostly taken from process context, but it is
102 * occasionally also taken from softirq/tasklet context, when
103 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
104 * But free_uid() is also called with local interrupts disabled, and running
105 * local_bh_enable() with local interrupts disabled is an error - we'll run
106 * softirq callbacks, and they can unconditionally enable interrupts, and
107 * the caller of free_uid() didn't expect that..
108 */
109static DEFINE_SPINLOCK(uidhash_lock);
110
111/* root_user.__count is 1, for init task cred */
112struct user_struct root_user = {
113 .__count = REFCOUNT_INIT(1),
114 .uid = GLOBAL_ROOT_UID,
115 .ratelimit = RATELIMIT_STATE_INIT(root_user.ratelimit, 0, 0),
116};
117
118/*
119 * These routines must be called with the uidhash spinlock held!
120 */
121static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
122{
123 hlist_add_head(&up->uidhash_node, hashent);
124}
125
126static void uid_hash_remove(struct user_struct *up)
127{
128 hlist_del_init(&up->uidhash_node);
129}
130
131static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent)
132{
133 struct user_struct *user;
134
135 hlist_for_each_entry(user, hashent, uidhash_node) {
136 if (uid_eq(user->uid, uid)) {
137 refcount_inc(&user->__count);
138 return user;
139 }
140 }
141
142 return NULL;
143}
144
145static int user_epoll_alloc(struct user_struct *up)
146{
147#ifdef CONFIG_EPOLL
148 return percpu_counter_init(&up->epoll_watches, 0, GFP_KERNEL);
149#else
150 return 0;
151#endif
152}
153
154static void user_epoll_free(struct user_struct *up)
155{
156#ifdef CONFIG_EPOLL
157 percpu_counter_destroy(&up->epoll_watches);
158#endif
159}
160
161/* IRQs are disabled and uidhash_lock is held upon function entry.
162 * IRQ state (as stored in flags) is restored and uidhash_lock released
163 * upon function exit.
164 */
165static void free_user(struct user_struct *up, unsigned long flags)
166 __releases(&uidhash_lock)
167{
168 uid_hash_remove(up);
169 spin_unlock_irqrestore(&uidhash_lock, flags);
170 user_epoll_free(up);
171 kmem_cache_free(uid_cachep, up);
172}
173
174/*
175 * Locate the user_struct for the passed UID. If found, take a ref on it. The
176 * caller must undo that ref with free_uid().
177 *
178 * If the user_struct could not be found, return NULL.
179 */
180struct user_struct *find_user(kuid_t uid)
181{
182 struct user_struct *ret;
183 unsigned long flags;
184
185 spin_lock_irqsave(&uidhash_lock, flags);
186 ret = uid_hash_find(uid, uidhashentry(uid));
187 spin_unlock_irqrestore(&uidhash_lock, flags);
188 return ret;
189}
190
191void free_uid(struct user_struct *up)
192{
193 unsigned long flags;
194
195 if (!up)
196 return;
197
198 if (refcount_dec_and_lock_irqsave(&up->__count, &uidhash_lock, &flags))
199 free_user(up, flags);
200}
201EXPORT_SYMBOL_GPL(free_uid);
202
203struct user_struct *alloc_uid(kuid_t uid)
204{
205 struct hlist_head *hashent = uidhashentry(uid);
206 struct user_struct *up, *new;
207
208 spin_lock_irq(&uidhash_lock);
209 up = uid_hash_find(uid, hashent);
210 spin_unlock_irq(&uidhash_lock);
211
212 if (!up) {
213 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
214 if (!new)
215 return NULL;
216
217 new->uid = uid;
218 refcount_set(&new->__count, 1);
219 if (user_epoll_alloc(new)) {
220 kmem_cache_free(uid_cachep, new);
221 return NULL;
222 }
223 ratelimit_state_init(&new->ratelimit, HZ, 100);
224 ratelimit_set_flags(&new->ratelimit, RATELIMIT_MSG_ON_RELEASE);
225
226 /*
227 * Before adding this, check whether we raced
228 * on adding the same user already..
229 */
230 spin_lock_irq(&uidhash_lock);
231 up = uid_hash_find(uid, hashent);
232 if (up) {
233 user_epoll_free(new);
234 kmem_cache_free(uid_cachep, new);
235 } else {
236 uid_hash_insert(new, hashent);
237 up = new;
238 }
239 spin_unlock_irq(&uidhash_lock);
240 }
241
242 return up;
243}
244
245static int __init uid_cache_init(void)
246{
247 int n;
248
249 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
250 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
251
252 for(n = 0; n < UIDHASH_SZ; ++n)
253 INIT_HLIST_HEAD(uidhash_table + n);
254
255 if (user_epoll_alloc(&root_user))
256 panic("root_user epoll percpu counter alloc failed");
257
258 /* Insert the root user immediately (init already runs as root) */
259 spin_lock_irq(&uidhash_lock);
260 uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
261 spin_unlock_irq(&uidhash_lock);
262
263 return 0;
264}
265subsys_initcall(uid_cache_init);