projects/linux·blob v2.6.27-rc5 · refs

526 lines · 12.4 KiB

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/module.h>
18#include <linux/user_namespace.h>
19
20struct user_namespace init_user_ns = {
21 .kref = {
22 .refcount = ATOMIC_INIT(2),
23 },
24 .root_user = &root_user,
25};
26EXPORT_SYMBOL_GPL(init_user_ns);
27
28/*
29 * UID task count cache, to get fast user lookup in "alloc_uid"
30 * when changing user ID's (ie setuid() and friends).
31 */
32
33#define UIDHASH_MASK (UIDHASH_SZ - 1)
34#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
35#define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid)))
36
37static struct kmem_cache *uid_cachep;
38
39/*
40 * The uidhash_lock is mostly taken from process context, but it is
41 * occasionally also taken from softirq/tasklet context, when
42 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
43 * But free_uid() is also called with local interrupts disabled, and running
44 * local_bh_enable() with local interrupts disabled is an error - we'll run
45 * softirq callbacks, and they can unconditionally enable interrupts, and
46 * the caller of free_uid() didn't expect that..
47 */
48static DEFINE_SPINLOCK(uidhash_lock);
49
50struct user_struct root_user = {
51 .__count = ATOMIC_INIT(1),
52 .processes = ATOMIC_INIT(1),
53 .files = ATOMIC_INIT(0),
54 .sigpending = ATOMIC_INIT(0),
55 .locked_shm = 0,
56#ifdef CONFIG_USER_SCHED
57 .tg = &init_task_group,
58#endif
59};
60
61/*
62 * These routines must be called with the uidhash spinlock held!
63 */
64static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
65{
66 hlist_add_head(&up->uidhash_node, hashent);
67}
68
69static void uid_hash_remove(struct user_struct *up)
70{
71 hlist_del_init(&up->uidhash_node);
72}
73
74static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
75{
76 struct user_struct *user;
77 struct hlist_node *h;
78
79 hlist_for_each_entry(user, h, hashent, uidhash_node) {
80 if (user->uid == uid) {
81 atomic_inc(&user->__count);
82 return user;
83 }
84 }
85
86 return NULL;
87}
88
89#ifdef CONFIG_USER_SCHED
90
91static void sched_destroy_user(struct user_struct *up)
92{
93 sched_destroy_group(up->tg);
94}
95
96static int sched_create_user(struct user_struct *up)
97{
98 int rc = 0;
99
100 up->tg = sched_create_group(&root_task_group);
101 if (IS_ERR(up->tg))
102 rc = -ENOMEM;
103
104 return rc;
105}
106
107static void sched_switch_user(struct task_struct *p)
108{
109 sched_move_task(p);
110}
111
112#else /* CONFIG_USER_SCHED */
113
114static void sched_destroy_user(struct user_struct *up) { }
115static int sched_create_user(struct user_struct *up) { return 0; }
116static void sched_switch_user(struct task_struct *p) { }
117
118#endif /* CONFIG_USER_SCHED */
119
120#if defined(CONFIG_USER_SCHED) && defined(CONFIG_SYSFS)
121
122static struct kset *uids_kset; /* represents the /sys/kernel/uids/ directory */
123static DEFINE_MUTEX(uids_mutex);
124
125static inline void uids_mutex_lock(void)
126{
127 mutex_lock(&uids_mutex);
128}
129
130static inline void uids_mutex_unlock(void)
131{
132 mutex_unlock(&uids_mutex);
133}
134
135/* uid directory attributes */
136#ifdef CONFIG_FAIR_GROUP_SCHED
137static ssize_t cpu_shares_show(struct kobject *kobj,
138 struct kobj_attribute *attr,
139 char *buf)
140{
141 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
142
143 return sprintf(buf, "%lu\n", sched_group_shares(up->tg));
144}
145
146static ssize_t cpu_shares_store(struct kobject *kobj,
147 struct kobj_attribute *attr,
148 const char *buf, size_t size)
149{
150 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
151 unsigned long shares;
152 int rc;
153
154 sscanf(buf, "%lu", &shares);
155
156 rc = sched_group_set_shares(up->tg, shares);
157
158 return (rc ? rc : size);
159}
160
161static struct kobj_attribute cpu_share_attr =
162 __ATTR(cpu_share, 0644, cpu_shares_show, cpu_shares_store);
163#endif
164
165#ifdef CONFIG_RT_GROUP_SCHED
166static ssize_t cpu_rt_runtime_show(struct kobject *kobj,
167 struct kobj_attribute *attr,
168 char *buf)
169{
170 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
171
172 return sprintf(buf, "%lu\n", sched_group_rt_runtime(up->tg));
173}
174
175static ssize_t cpu_rt_runtime_store(struct kobject *kobj,
176 struct kobj_attribute *attr,
177 const char *buf, size_t size)
178{
179 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
180 unsigned long rt_runtime;
181 int rc;
182
183 sscanf(buf, "%lu", &rt_runtime);
184
185 rc = sched_group_set_rt_runtime(up->tg, rt_runtime);
186
187 return (rc ? rc : size);
188}
189
190static struct kobj_attribute cpu_rt_runtime_attr =
191 __ATTR(cpu_rt_runtime, 0644, cpu_rt_runtime_show, cpu_rt_runtime_store);
192
193static ssize_t cpu_rt_period_show(struct kobject *kobj,
194 struct kobj_attribute *attr,
195 char *buf)
196{
197 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
198
199 return sprintf(buf, "%lu\n", sched_group_rt_period(up->tg));
200}
201
202static ssize_t cpu_rt_period_store(struct kobject *kobj,
203 struct kobj_attribute *attr,
204 const char *buf, size_t size)
205{
206 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
207 unsigned long rt_period;
208 int rc;
209
210 sscanf(buf, "%lu", &rt_period);
211
212 rc = sched_group_set_rt_period(up->tg, rt_period);
213
214 return (rc ? rc : size);
215}
216
217static struct kobj_attribute cpu_rt_period_attr =
218 __ATTR(cpu_rt_period, 0644, cpu_rt_period_show, cpu_rt_period_store);
219#endif
220
221/* default attributes per uid directory */
222static struct attribute *uids_attributes[] = {
223#ifdef CONFIG_FAIR_GROUP_SCHED
224 &cpu_share_attr.attr,
225#endif
226#ifdef CONFIG_RT_GROUP_SCHED
227 &cpu_rt_runtime_attr.attr,
228 &cpu_rt_period_attr.attr,
229#endif
230 NULL
231};
232
233/* the lifetime of user_struct is not managed by the core (now) */
234static void uids_release(struct kobject *kobj)
235{
236 return;
237}
238
239static struct kobj_type uids_ktype = {
240 .sysfs_ops = &kobj_sysfs_ops,
241 .default_attrs = uids_attributes,
242 .release = uids_release,
243};
244
245/* create /sys/kernel/uids/<uid>/cpu_share file for this user */
246static int uids_user_create(struct user_struct *up)
247{
248 struct kobject *kobj = &up->kobj;
249 int error;
250
251 memset(kobj, 0, sizeof(struct kobject));
252 kobj->kset = uids_kset;
253 error = kobject_init_and_add(kobj, &uids_ktype, NULL, "%d", up->uid);
254 if (error) {
255 kobject_put(kobj);
256 goto done;
257 }
258
259 kobject_uevent(kobj, KOBJ_ADD);
260done:
261 return error;
262}
263
264/* create these entries in sysfs:
265 * "/sys/kernel/uids" directory
266 * "/sys/kernel/uids/0" directory (for root user)
267 * "/sys/kernel/uids/0/cpu_share" file (for root user)
268 */
269int __init uids_sysfs_init(void)
270{
271 uids_kset = kset_create_and_add("uids", NULL, kernel_kobj);
272 if (!uids_kset)
273 return -ENOMEM;
274
275 return uids_user_create(&root_user);
276}
277
278/* work function to remove sysfs directory for a user and free up
279 * corresponding structures.
280 */
281static void remove_user_sysfs_dir(struct work_struct *w)
282{
283 struct user_struct *up = container_of(w, struct user_struct, work);
284 unsigned long flags;
285 int remove_user = 0;
286
287 /* Make uid_hash_remove() + sysfs_remove_file() + kobject_del()
288 * atomic.
289 */
290 uids_mutex_lock();
291
292 local_irq_save(flags);
293
294 if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
295 uid_hash_remove(up);
296 remove_user = 1;
297 spin_unlock_irqrestore(&uidhash_lock, flags);
298 } else {
299 local_irq_restore(flags);
300 }
301
302 if (!remove_user)
303 goto done;
304
305 kobject_uevent(&up->kobj, KOBJ_REMOVE);
306 kobject_del(&up->kobj);
307 kobject_put(&up->kobj);
308
309 sched_destroy_user(up);
310 key_put(up->uid_keyring);
311 key_put(up->session_keyring);
312 kmem_cache_free(uid_cachep, up);
313
314done:
315 uids_mutex_unlock();
316}
317
318/* IRQs are disabled and uidhash_lock is held upon function entry.
319 * IRQ state (as stored in flags) is restored and uidhash_lock released
320 * upon function exit.
321 */
322static inline void free_user(struct user_struct *up, unsigned long flags)
323{
324 /* restore back the count */
325 atomic_inc(&up->__count);
326 spin_unlock_irqrestore(&uidhash_lock, flags);
327
328 INIT_WORK(&up->work, remove_user_sysfs_dir);
329 schedule_work(&up->work);
330}
331
332#else /* CONFIG_USER_SCHED && CONFIG_SYSFS */
333
334int uids_sysfs_init(void) { return 0; }
335static inline int uids_user_create(struct user_struct *up) { return 0; }
336static inline void uids_mutex_lock(void) { }
337static inline void uids_mutex_unlock(void) { }
338
339/* IRQs are disabled and uidhash_lock is held upon function entry.
340 * IRQ state (as stored in flags) is restored and uidhash_lock released
341 * upon function exit.
342 */
343static inline void free_user(struct user_struct *up, unsigned long flags)
344{
345 uid_hash_remove(up);
346 spin_unlock_irqrestore(&uidhash_lock, flags);
347 sched_destroy_user(up);
348 key_put(up->uid_keyring);
349 key_put(up->session_keyring);
350 kmem_cache_free(uid_cachep, up);
351}
352
353#endif
354
355/*
356 * Locate the user_struct for the passed UID. If found, take a ref on it. The
357 * caller must undo that ref with free_uid().
358 *
359 * If the user_struct could not be found, return NULL.
360 */
361struct user_struct *find_user(uid_t uid)
362{
363 struct user_struct *ret;
364 unsigned long flags;
365 struct user_namespace *ns = current->nsproxy->user_ns;
366
367 spin_lock_irqsave(&uidhash_lock, flags);
368 ret = uid_hash_find(uid, uidhashentry(ns, uid));
369 spin_unlock_irqrestore(&uidhash_lock, flags);
370 return ret;
371}
372
373void free_uid(struct user_struct *up)
374{
375 unsigned long flags;
376
377 if (!up)
378 return;
379
380 local_irq_save(flags);
381 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
382 free_user(up, flags);
383 else
384 local_irq_restore(flags);
385}
386
387struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid)
388{
389 struct hlist_head *hashent = uidhashentry(ns, uid);
390 struct user_struct *up, *new;
391
392 /* Make uid_hash_find() + uids_user_create() + uid_hash_insert()
393 * atomic.
394 */
395 uids_mutex_lock();
396
397 spin_lock_irq(&uidhash_lock);
398 up = uid_hash_find(uid, hashent);
399 spin_unlock_irq(&uidhash_lock);
400
401 if (!up) {
402 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
403 if (!new)
404 goto out_unlock;
405
406 new->uid = uid;
407 atomic_set(&new->__count, 1);
408
409 if (sched_create_user(new) < 0)
410 goto out_free_user;
411
412 if (uids_user_create(new))
413 goto out_destoy_sched;
414
415 /*
416 * Before adding this, check whether we raced
417 * on adding the same user already..
418 */
419 spin_lock_irq(&uidhash_lock);
420 up = uid_hash_find(uid, hashent);
421 if (up) {
422 /* This case is not possible when CONFIG_USER_SCHED
423 * is defined, since we serialize alloc_uid() using
424 * uids_mutex. Hence no need to call
425 * sched_destroy_user() or remove_user_sysfs_dir().
426 */
427 key_put(new->uid_keyring);
428 key_put(new->session_keyring);
429 kmem_cache_free(uid_cachep, new);
430 } else {
431 uid_hash_insert(new, hashent);
432 up = new;
433 }
434 spin_unlock_irq(&uidhash_lock);
435
436 }
437
438 uids_mutex_unlock();
439
440 return up;
441
442out_destoy_sched:
443 sched_destroy_user(new);
444out_free_user:
445 kmem_cache_free(uid_cachep, new);
446out_unlock:
447 uids_mutex_unlock();
448 return NULL;
449}
450
451void switch_uid(struct user_struct *new_user)
452{
453 struct user_struct *old_user;
454
455 /* What if a process setreuid()'s and this brings the
456 * new uid over his NPROC rlimit? We can check this now
457 * cheaply with the new uid cache, so if it matters
458 * we should be checking for it. -DaveM
459 */
460 old_user = current->user;
461 atomic_inc(&new_user->processes);
462 atomic_dec(&old_user->processes);
463 switch_uid_keyring(new_user);
464 current->user = new_user;
465 sched_switch_user(current);
466
467 /*
468 * We need to synchronize with __sigqueue_alloc()
469 * doing a get_uid(p->user).. If that saw the old
470 * user value, we need to wait until it has exited
471 * its critical region before we can free the old
472 * structure.
473 */
474 smp_mb();
475 spin_unlock_wait(&current->sighand->siglock);
476
477 free_uid(old_user);
478 suid_keys(current);
479}
480
481#ifdef CONFIG_USER_NS
482void release_uids(struct user_namespace *ns)
483{
484 int i;
485 unsigned long flags;
486 struct hlist_head *head;
487 struct hlist_node *nd;
488
489 spin_lock_irqsave(&uidhash_lock, flags);
490 /*
491 * collapse the chains so that the user_struct-s will
492 * be still alive, but not in hashes. subsequent free_uid()
493 * will free them.
494 */
495 for (i = 0; i < UIDHASH_SZ; i++) {
496 head = ns->uidhash_table + i;
497 while (!hlist_empty(head)) {
498 nd = head->first;
499 hlist_del_init(nd);
500 }
501 }
502 spin_unlock_irqrestore(&uidhash_lock, flags);
503
504 free_uid(ns->root_user);
505}
506#endif
507
508static int __init uid_cache_init(void)
509{
510 int n;
511
512 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
513 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
514
515 for(n = 0; n < UIDHASH_SZ; ++n)
516 INIT_HLIST_HEAD(init_user_ns.uidhash_table + n);
517
518 /* Insert the root user immediately (init already runs as root) */
519 spin_lock_irq(&uidhash_lock);
520 uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
521 spin_unlock_irq(&uidhash_lock);
522
523 return 0;
524}
525
526module_init(uid_cache_init);