4 * (C) Copyright 1991-2000 Linus Torvalds
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.
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/module.h>
18 #include <linux/user_namespace.h>
21 * UID task count cache, to get fast user lookup in "alloc_uid"
22 * when changing user ID's (ie setuid() and friends).
25 #define UIDHASH_MASK (UIDHASH_SZ - 1)
26 #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
27 #define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid)))
29 static struct kmem_cache
*uid_cachep
;
32 * The uidhash_lock is mostly taken from process context, but it is
33 * occasionally also taken from softirq/tasklet context, when
34 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
35 * But free_uid() is also called with local interrupts disabled, and running
36 * local_bh_enable() with local interrupts disabled is an error - we'll run
37 * softirq callbacks, and they can unconditionally enable interrupts, and
38 * the caller of free_uid() didn't expect that..
40 static DEFINE_SPINLOCK(uidhash_lock
);
42 struct user_struct root_user
= {
43 .__count
= ATOMIC_INIT(1),
44 .processes
= ATOMIC_INIT(1),
45 .files
= ATOMIC_INIT(0),
46 .sigpending
= ATOMIC_INIT(0),
50 .uid_keyring
= &root_user_keyring
,
51 .session_keyring
= &root_session_keyring
,
53 #ifdef CONFIG_FAIR_USER_SCHED
54 .tg
= &init_task_group
,
59 * These routines must be called with the uidhash spinlock held!
61 static inline void uid_hash_insert(struct user_struct
*up
,
62 struct hlist_head
*hashent
)
64 hlist_add_head(&up
->uidhash_node
, hashent
);
67 static inline void uid_hash_remove(struct user_struct
*up
)
69 hlist_del_init(&up
->uidhash_node
);
72 static inline struct user_struct
*uid_hash_find(uid_t uid
,
73 struct hlist_head
*hashent
)
75 struct user_struct
*user
;
78 hlist_for_each_entry(user
, h
, hashent
, uidhash_node
) {
79 if (user
->uid
== uid
) {
80 atomic_inc(&user
->__count
);
88 #ifdef CONFIG_FAIR_USER_SCHED
90 static struct kobject uids_kobject
; /* represents /sys/kernel/uids directory */
91 static DEFINE_MUTEX(uids_mutex
);
93 static void sched_destroy_user(struct user_struct
*up
)
95 sched_destroy_group(up
->tg
);
98 static int sched_create_user(struct user_struct
*up
)
102 up
->tg
= sched_create_group();
109 static void sched_switch_user(struct task_struct
*p
)
114 static inline void uids_mutex_lock(void)
116 mutex_lock(&uids_mutex
);
119 static inline void uids_mutex_unlock(void)
121 mutex_unlock(&uids_mutex
);
124 /* return cpu shares held by the user */
125 ssize_t
cpu_shares_show(struct kset
*kset
, char *buffer
)
127 struct user_struct
*up
= container_of(kset
, struct user_struct
, kset
);
129 return sprintf(buffer
, "%lu\n", sched_group_shares(up
->tg
));
132 /* modify cpu shares held by the user */
133 ssize_t
cpu_shares_store(struct kset
*kset
, const char *buffer
, size_t size
)
135 struct user_struct
*up
= container_of(kset
, struct user_struct
, kset
);
136 unsigned long shares
;
139 sscanf(buffer
, "%lu", &shares
);
141 rc
= sched_group_set_shares(up
->tg
, shares
);
143 return (rc
? rc
: size
);
146 static void user_attr_init(struct subsys_attribute
*sa
, char *name
, int mode
)
148 sa
->attr
.name
= name
;
149 sa
->attr
.mode
= mode
;
150 sa
->show
= cpu_shares_show
;
151 sa
->store
= cpu_shares_store
;
154 /* Create "/sys/kernel/uids/<uid>" directory and
155 * "/sys/kernel/uids/<uid>/cpu_share" file for this user.
157 static int user_kobject_create(struct user_struct
*up
)
159 struct kset
*kset
= &up
->kset
;
160 struct kobject
*kobj
= &kset
->kobj
;
163 memset(kset
, 0, sizeof(struct kset
));
164 kobj
->parent
= &uids_kobject
; /* create under /sys/kernel/uids dir */
165 kobject_set_name(kobj
, "%d", up
->uid
);
167 user_attr_init(&up
->user_attr
, "cpu_share", 0644);
169 error
= kobject_add(kobj
);
173 error
= sysfs_create_file(kobj
, &up
->user_attr
.attr
);
181 /* create these in sysfs filesystem:
182 * "/sys/kernel/uids" directory
183 * "/sys/kernel/uids/0" directory (for root user)
184 * "/sys/kernel/uids/0/cpu_share" file (for root user)
186 int __init
uids_kobject_init(void)
190 /* create under /sys/kernel dir */
191 uids_kobject
.parent
= &kernel_subsys
.kobj
;
192 kobject_set_name(&uids_kobject
, "uids");
193 kobject_init(&uids_kobject
);
195 error
= kobject_add(&uids_kobject
);
197 error
= user_kobject_create(&root_user
);
202 /* work function to remove sysfs directory for a user and free up
203 * corresponding structures.
205 static void remove_user_sysfs_dir(struct work_struct
*w
)
207 struct user_struct
*up
= container_of(w
, struct user_struct
, work
);
208 struct kobject
*kobj
= &up
->kset
.kobj
;
212 /* Make uid_hash_remove() + sysfs_remove_file() + kobject_del()
217 local_irq_save(flags
);
219 if (atomic_dec_and_lock(&up
->__count
, &uidhash_lock
)) {
222 spin_unlock_irqrestore(&uidhash_lock
, flags
);
224 local_irq_restore(flags
);
230 sysfs_remove_file(kobj
, &up
->user_attr
.attr
);
233 sched_destroy_user(up
);
234 key_put(up
->uid_keyring
);
235 key_put(up
->session_keyring
);
236 kmem_cache_free(uid_cachep
, up
);
242 /* IRQs are disabled and uidhash_lock is held upon function entry.
243 * IRQ state (as stored in flags) is restored and uidhash_lock released
244 * upon function exit.
246 static inline void free_user(struct user_struct
*up
, unsigned long flags
)
248 /* restore back the count */
249 atomic_inc(&up
->__count
);
250 spin_unlock_irqrestore(&uidhash_lock
, flags
);
252 INIT_WORK(&up
->work
, remove_user_sysfs_dir
);
253 schedule_work(&up
->work
);
256 #else /* CONFIG_FAIR_USER_SCHED */
258 static void sched_destroy_user(struct user_struct
*up
) { }
259 static int sched_create_user(struct user_struct
*up
) { return 0; }
260 static void sched_switch_user(struct task_struct
*p
) { }
261 static inline int user_kobject_create(struct user_struct
*up
) { return 0; }
262 static inline void uids_mutex_lock(void) { }
263 static inline void uids_mutex_unlock(void) { }
265 /* IRQs are disabled and uidhash_lock is held upon function entry.
266 * IRQ state (as stored in flags) is restored and uidhash_lock released
267 * upon function exit.
269 static inline void free_user(struct user_struct
*up
, unsigned long flags
)
272 spin_unlock_irqrestore(&uidhash_lock
, flags
);
273 sched_destroy_user(up
);
274 key_put(up
->uid_keyring
);
275 key_put(up
->session_keyring
);
276 kmem_cache_free(uid_cachep
, up
);
279 #endif /* CONFIG_FAIR_USER_SCHED */
282 * Locate the user_struct for the passed UID. If found, take a ref on it. The
283 * caller must undo that ref with free_uid().
285 * If the user_struct could not be found, return NULL.
287 struct user_struct
*find_user(uid_t uid
)
289 struct user_struct
*ret
;
291 struct user_namespace
*ns
= current
->nsproxy
->user_ns
;
293 spin_lock_irqsave(&uidhash_lock
, flags
);
294 ret
= uid_hash_find(uid
, uidhashentry(ns
, uid
));
295 spin_unlock_irqrestore(&uidhash_lock
, flags
);
299 void free_uid(struct user_struct
*up
)
306 local_irq_save(flags
);
307 if (atomic_dec_and_lock(&up
->__count
, &uidhash_lock
))
308 free_user(up
, flags
);
310 local_irq_restore(flags
);
313 struct user_struct
* alloc_uid(struct user_namespace
*ns
, uid_t uid
)
315 struct hlist_head
*hashent
= uidhashentry(ns
, uid
);
316 struct user_struct
*up
;
318 /* Make uid_hash_find() + user_kobject_create() + uid_hash_insert()
323 spin_lock_irq(&uidhash_lock
);
324 up
= uid_hash_find(uid
, hashent
);
325 spin_unlock_irq(&uidhash_lock
);
328 struct user_struct
*new;
330 new = kmem_cache_alloc(uid_cachep
, GFP_KERNEL
);
334 atomic_set(&new->__count
, 1);
335 atomic_set(&new->processes
, 0);
336 atomic_set(&new->files
, 0);
337 atomic_set(&new->sigpending
, 0);
338 #ifdef CONFIG_INOTIFY_USER
339 atomic_set(&new->inotify_watches
, 0);
340 atomic_set(&new->inotify_devs
, 0);
346 if (alloc_uid_keyring(new, current
) < 0) {
347 kmem_cache_free(uid_cachep
, new);
351 if (sched_create_user(new) < 0) {
352 key_put(new->uid_keyring
);
353 key_put(new->session_keyring
);
354 kmem_cache_free(uid_cachep
, new);
358 if (user_kobject_create(new)) {
359 sched_destroy_user(new);
360 key_put(new->uid_keyring
);
361 key_put(new->session_keyring
);
362 kmem_cache_free(uid_cachep
, new);
368 * Before adding this, check whether we raced
369 * on adding the same user already..
371 spin_lock_irq(&uidhash_lock
);
372 up
= uid_hash_find(uid
, hashent
);
374 /* This case is not possible when CONFIG_FAIR_USER_SCHED
375 * is defined, since we serialize alloc_uid() using
376 * uids_mutex. Hence no need to call
377 * sched_destroy_user() or remove_user_sysfs_dir().
379 key_put(new->uid_keyring
);
380 key_put(new->session_keyring
);
381 kmem_cache_free(uid_cachep
, new);
383 uid_hash_insert(new, hashent
);
386 spin_unlock_irq(&uidhash_lock
);
395 void switch_uid(struct user_struct
*new_user
)
397 struct user_struct
*old_user
;
399 /* What if a process setreuid()'s and this brings the
400 * new uid over his NPROC rlimit? We can check this now
401 * cheaply with the new uid cache, so if it matters
402 * we should be checking for it. -DaveM
404 old_user
= current
->user
;
405 atomic_inc(&new_user
->processes
);
406 atomic_dec(&old_user
->processes
);
407 switch_uid_keyring(new_user
);
408 current
->user
= new_user
;
409 sched_switch_user(current
);
412 * We need to synchronize with __sigqueue_alloc()
413 * doing a get_uid(p->user).. If that saw the old
414 * user value, we need to wait until it has exited
415 * its critical region before we can free the old
419 spin_unlock_wait(¤t
->sighand
->siglock
);
425 void release_uids(struct user_namespace
*ns
)
429 struct hlist_head
*head
;
430 struct hlist_node
*nd
;
432 spin_lock_irqsave(&uidhash_lock
, flags
);
434 * collapse the chains so that the user_struct-s will
435 * be still alive, but not in hashes. subsequent free_uid()
438 for (i
= 0; i
< UIDHASH_SZ
; i
++) {
439 head
= ns
->uidhash_table
+ i
;
440 while (!hlist_empty(head
)) {
445 spin_unlock_irqrestore(&uidhash_lock
, flags
);
447 free_uid(ns
->root_user
);
450 static int __init
uid_cache_init(void)
454 uid_cachep
= kmem_cache_create("uid_cache", sizeof(struct user_struct
),
455 0, SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
);
457 for(n
= 0; n
< UIDHASH_SZ
; ++n
)
458 INIT_HLIST_HEAD(init_user_ns
.uidhash_table
+ n
);
460 /* Insert the root user immediately (init already runs as root) */
461 spin_lock_irq(&uidhash_lock
);
462 uid_hash_insert(&root_user
, uidhashentry(&init_user_ns
, 0));
463 spin_unlock_irq(&uidhash_lock
);
468 module_init(uid_cache_init
);