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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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>
Ingo Molnar4021cb22006-01-25 15:23:07 +010016#include <linux/interrupt.h>
Paul Gortmaker9984de12011-05-23 14:51:41 -040017#include <linux/export.h>
Cedric Le Goateracce2922007-07-15 23:40:59 -070018#include <linux/user_namespace.h>
SamarV-121b5757112020-09-21 05:47:44 +000019#include <linux/proc_fs.h>
David Howells0bb80f22013-04-12 01:50:06 +010020#include <linux/proc_ns.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070021
Serge E. Hallyn59607db2011-03-23 16:43:16 -070022/*
23 * userns count is 1 for root user, 1 for init_uts_ns,
24 * and 1 for... ?
25 */
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080026struct user_namespace init_user_ns = {
Eric W. Biederman22d917d2011-11-17 00:11:58 -080027 .uid_map = {
28 .nr_extents = 1,
29 .extent[0] = {
30 .first = 0,
31 .lower_first = 0,
Eric W. Biederman4b06a812012-05-19 15:44:06 -060032 .count = 4294967295U,
Eric W. Biederman22d917d2011-11-17 00:11:58 -080033 },
34 },
35 .gid_map = {
36 .nr_extents = 1,
37 .extent[0] = {
38 .first = 0,
39 .lower_first = 0,
Eric W. Biederman4b06a812012-05-19 15:44:06 -060040 .count = 4294967295U,
Eric W. Biederman22d917d2011-11-17 00:11:58 -080041 },
42 },
Eric W. Biedermanf76d2072012-08-30 01:24:05 -070043 .projid_map = {
44 .nr_extents = 1,
45 .extent[0] = {
46 .first = 0,
47 .lower_first = 0,
48 .count = 4294967295U,
49 },
50 },
Eric W. Biedermanc61a2812012-12-28 18:58:39 -080051 .count = ATOMIC_INIT(3),
Eric W. Biederman783291e2011-11-17 01:32:59 -080052 .owner = GLOBAL_ROOT_UID,
53 .group = GLOBAL_ROOT_GID,
Al Viro435d5f42014-10-31 22:56:04 -040054 .ns.inum = PROC_USER_INIT_INO,
Al Viro33c42942014-11-01 02:32:53 -040055#ifdef CONFIG_USER_NS
56 .ns.ops = &userns_operations,
57#endif
Eric W. Biederman9cc46512014-12-02 12:27:26 -060058 .flags = USERNS_INIT_FLAGS,
Xiao Guangrong6bd364d2013-12-13 15:00:32 +080059#ifdef CONFIG_PERSISTENT_KEYRINGS
60 .persistent_keyring_register_sem =
61 __RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),
David Howellsf36f8c72013-09-24 10:35:19 +010062#endif
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080063};
64EXPORT_SYMBOL_GPL(init_user_ns);
65
Linus Torvalds1da177e2005-04-16 15:20:36 -070066/*
67 * UID task count cache, to get fast user lookup in "alloc_uid"
68 * when changing user ID's (ie setuid() and friends).
69 */
70
Eric W. Biederman7b44ab92011-11-16 23:20:58 -080071#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
72#define UIDHASH_SZ (1 << UIDHASH_BITS)
Linus Torvalds1da177e2005-04-16 15:20:36 -070073#define UIDHASH_MASK (UIDHASH_SZ - 1)
74#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
Eric W. Biederman7b44ab92011-11-16 23:20:58 -080075#define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid))))
Linus Torvalds1da177e2005-04-16 15:20:36 -070076
Christoph Lametere18b8902006-12-06 20:33:20 -080077static struct kmem_cache *uid_cachep;
Eric W. Biederman7b44ab92011-11-16 23:20:58 -080078struct hlist_head uidhash_table[UIDHASH_SZ];
Ingo Molnar4021cb22006-01-25 15:23:07 +010079
80/*
81 * The uidhash_lock is mostly taken from process context, but it is
82 * occasionally also taken from softirq/tasklet context, when
83 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
Andrew Morton3fa97c92006-01-31 16:34:26 -080084 * But free_uid() is also called with local interrupts disabled, and running
85 * local_bh_enable() with local interrupts disabled is an error - we'll run
86 * softirq callbacks, and they can unconditionally enable interrupts, and
87 * the caller of free_uid() didn't expect that..
Ingo Molnar4021cb22006-01-25 15:23:07 +010088 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070089static DEFINE_SPINLOCK(uidhash_lock);
90
Eric W. Biederman783291e2011-11-17 01:32:59 -080091/* root_user.__count is 1, for init task cred */
Linus Torvalds1da177e2005-04-16 15:20:36 -070092struct user_struct root_user = {
Eric W. Biederman783291e2011-11-17 01:32:59 -080093 .__count = ATOMIC_INIT(1),
Linus Torvalds1da177e2005-04-16 15:20:36 -070094 .processes = ATOMIC_INIT(1),
Linus Torvalds1da177e2005-04-16 15:20:36 -070095 .sigpending = ATOMIC_INIT(0),
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 .locked_shm = 0,
Eric W. Biederman7b44ab92011-11-16 23:20:58 -080097 .uid = GLOBAL_ROOT_UID,
Linus Torvalds1da177e2005-04-16 15:20:36 -070098};
99
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200100/*
101 * These routines must be called with the uidhash spinlock held!
102 */
Alexey Dobriyan40aeb402007-10-16 23:30:09 -0700103static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200104{
105 hlist_add_head(&up->uidhash_node, hashent);
106}
107
Alexey Dobriyan40aeb402007-10-16 23:30:09 -0700108static void uid_hash_remove(struct user_struct *up)
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200109{
110 hlist_del_init(&up->uidhash_node);
111}
112
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800113static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent)
Kay Sievers39592142009-03-24 15:43:30 +0100114{
115 struct user_struct *user;
Kay Sievers39592142009-03-24 15:43:30 +0100116
Sasha Levinb67bfe02013-02-27 17:06:00 -0800117 hlist_for_each_entry(user, hashent, uidhash_node) {
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800118 if (uid_eq(user->uid, uid)) {
Kay Sievers39592142009-03-24 15:43:30 +0100119 atomic_inc(&user->__count);
120 return user;
121 }
122 }
123
124 return NULL;
125}
126
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200127/* IRQs are disabled and uidhash_lock is held upon function entry.
128 * IRQ state (as stored in flags) is restored and uidhash_lock released
129 * upon function exit.
130 */
Serge Hallyn18b6e042008-10-15 16:38:45 -0500131static void free_user(struct user_struct *up, unsigned long flags)
Namhyung Kim571428b2010-10-26 14:22:43 -0700132 __releases(&uidhash_lock)
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200133{
134 uid_hash_remove(up);
135 spin_unlock_irqrestore(&uidhash_lock, flags);
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200136 key_put(up->uid_keyring);
137 key_put(up->session_keyring);
138 kmem_cache_free(uid_cachep, up);
139}
Srivatsa Vaddagiri24e377a2007-10-15 17:00:09 +0200140
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142 * Locate the user_struct for the passed UID. If found, take a ref on it. The
143 * caller must undo that ref with free_uid().
144 *
145 * If the user_struct could not be found, return NULL.
146 */
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800147struct user_struct *find_user(kuid_t uid)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148{
149 struct user_struct *ret;
Andrew Morton3fa97c92006-01-31 16:34:26 -0800150 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151
Andrew Morton3fa97c92006-01-31 16:34:26 -0800152 spin_lock_irqsave(&uidhash_lock, flags);
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800153 ret = uid_hash_find(uid, uidhashentry(uid));
Andrew Morton3fa97c92006-01-31 16:34:26 -0800154 spin_unlock_irqrestore(&uidhash_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155 return ret;
156}
157
158void free_uid(struct user_struct *up)
159{
Andrew Morton3fa97c92006-01-31 16:34:26 -0800160 unsigned long flags;
161
Andrew Morton36f57412006-03-24 03:15:47 -0800162 if (!up)
163 return;
164
Andrew Morton3fa97c92006-01-31 16:34:26 -0800165 local_irq_save(flags);
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200166 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
167 free_user(up, flags);
168 else
Andrew Morton36f57412006-03-24 03:15:47 -0800169 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170}
171
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800172struct user_struct *alloc_uid(kuid_t uid)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173{
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800174 struct hlist_head *hashent = uidhashentry(uid);
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100175 struct user_struct *up, *new;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176
Andrew Morton3fa97c92006-01-31 16:34:26 -0800177 spin_lock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178 up = uid_hash_find(uid, hashent);
Andrew Morton3fa97c92006-01-31 16:34:26 -0800179 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180
181 if (!up) {
Andrew Morton354a1f42008-04-30 00:54:54 -0700182 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100183 if (!new)
184 goto out_unlock;
Pavel Emelyanov5e8869b2007-11-26 21:21:49 +0100185
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186 new->uid = uid;
187 atomic_set(&new->__count, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188
189 /*
190 * Before adding this, check whether we raced
191 * on adding the same user already..
192 */
Andrew Morton3fa97c92006-01-31 16:34:26 -0800193 spin_lock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194 up = uid_hash_find(uid, hashent);
195 if (up) {
196 key_put(new->uid_keyring);
197 key_put(new->session_keyring);
198 kmem_cache_free(uid_cachep, new);
199 } else {
200 uid_hash_insert(new, hashent);
201 up = new;
202 }
Andrew Morton3fa97c92006-01-31 16:34:26 -0800203 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204 }
SamarV-121b5757112020-09-21 05:47:44 +0000205 proc_register_uid(uid);
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200206
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207 return up;
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100208
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100209out_unlock:
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100210 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700211}
212
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213static int __init uid_cache_init(void)
214{
215 int n;
216
217 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
Paul Mundt20c2df82007-07-20 10:11:58 +0900218 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219
220 for(n = 0; n < UIDHASH_SZ; ++n)
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800221 INIT_HLIST_HEAD(uidhash_table + n);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222
223 /* Insert the root user immediately (init already runs as root) */
Andrew Morton3fa97c92006-01-31 16:34:26 -0800224 spin_lock_irq(&uidhash_lock);
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800225 uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
Andrew Morton3fa97c92006-01-31 16:34:26 -0800226 spin_unlock_irq(&uidhash_lock);
SamarV-121b5757112020-09-21 05:47:44 +0000227 proc_register_uid(GLOBAL_ROOT_UID);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700228
229 return 0;
230}
Paul Gortmakerc96d66602014-04-03 14:48:35 -0700231subsys_initcall(uid_cache_init);