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