projects/linux·blob v2.6.30 · refs

499 lines · 11.8 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#include "cred-internals.h"
20
21struct user_namespace init_user_ns = {
22 .kref = {
23 .refcount = ATOMIC_INIT(2),
24 },
25 .creator = &root_user,
26};
27EXPORT_SYMBOL_GPL(init_user_ns);
28
29/*
30 * UID task count cache, to get fast user lookup in "alloc_uid"
31 * when changing user ID's (ie setuid() and friends).
32 */
33
34#define UIDHASH_MASK (UIDHASH_SZ - 1)
35#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
36#define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid)))
37
38static struct kmem_cache *uid_cachep;
39
40/*
41 * The uidhash_lock is mostly taken from process context, but it is
42 * occasionally also taken from softirq/tasklet context, when
43 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
44 * But free_uid() is also called with local interrupts disabled, and running
45 * local_bh_enable() with local interrupts disabled is an error - we'll run
46 * softirq callbacks, and they can unconditionally enable interrupts, and
47 * the caller of free_uid() didn't expect that..
48 */
49static DEFINE_SPINLOCK(uidhash_lock);
50
51/* root_user.__count is 2, 1 for init task cred, 1 for init_user_ns->creator */
52struct user_struct root_user = {
53 .__count = ATOMIC_INIT(2),
54 .processes = ATOMIC_INIT(1),
55 .files = ATOMIC_INIT(0),
56 .sigpending = ATOMIC_INIT(0),
57 .locked_shm = 0,
58 .user_ns = &init_user_ns,
59#ifdef CONFIG_USER_SCHED
60 .tg = &init_task_group,
61#endif
62};
63
64/*
65 * These routines must be called with the uidhash spinlock held!
66 */
67static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
68{
69 hlist_add_head(&up->uidhash_node, hashent);
70}
71
72static void uid_hash_remove(struct user_struct *up)
73{
74 hlist_del_init(&up->uidhash_node);
75 put_user_ns(up->user_ns);
76}
77
78static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
79{
80 struct user_struct *user;
81 struct hlist_node *h;
82
83 hlist_for_each_entry(user, h, hashent, uidhash_node) {
84 if (user->uid == uid) {
85 atomic_inc(&user->__count);
86 return user;
87 }
88 }
89
90 return NULL;
91}
92
93#ifdef CONFIG_USER_SCHED
94
95static void sched_destroy_user(struct user_struct *up)
96{
97 sched_destroy_group(up->tg);
98}
99
100static int sched_create_user(struct user_struct *up)
101{
102 int rc = 0;
103
104 up->tg = sched_create_group(&root_task_group);
105 if (IS_ERR(up->tg))
106 rc = -ENOMEM;
107
108 set_tg_uid(up);
109
110 return rc;
111}
112
113#else /* CONFIG_USER_SCHED */
114
115static void sched_destroy_user(struct user_struct *up) { }
116static int sched_create_user(struct user_struct *up) { return 0; }
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, "%ld\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, "%ld", &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/*
246 * Create /sys/kernel/uids/<uid>/cpu_share file for this user
247 * We do not create this file for users in a user namespace (until
248 * sysfs tagging is implemented).
249 *
250 * See Documentation/scheduler/sched-design-CFS.txt for ramifications.
251 */
252static int uids_user_create(struct user_struct *up)
253{
254 struct kobject *kobj = &up->kobj;
255 int error;
256
257 memset(kobj, 0, sizeof(struct kobject));
258 if (up->user_ns != &init_user_ns)
259 return 0;
260 kobj->kset = uids_kset;
261 error = kobject_init_and_add(kobj, &uids_ktype, NULL, "%d", up->uid);
262 if (error) {
263 kobject_put(kobj);
264 goto done;
265 }
266
267 kobject_uevent(kobj, KOBJ_ADD);
268done:
269 return error;
270}
271
272/* create these entries in sysfs:
273 * "/sys/kernel/uids" directory
274 * "/sys/kernel/uids/0" directory (for root user)
275 * "/sys/kernel/uids/0/cpu_share" file (for root user)
276 */
277int __init uids_sysfs_init(void)
278{
279 uids_kset = kset_create_and_add("uids", NULL, kernel_kobj);
280 if (!uids_kset)
281 return -ENOMEM;
282
283 return uids_user_create(&root_user);
284}
285
286/* work function to remove sysfs directory for a user and free up
287 * corresponding structures.
288 */
289static void cleanup_user_struct(struct work_struct *w)
290{
291 struct user_struct *up = container_of(w, struct user_struct, work);
292 unsigned long flags;
293 int remove_user = 0;
294
295 /* Make uid_hash_remove() + sysfs_remove_file() + kobject_del()
296 * atomic.
297 */
298 uids_mutex_lock();
299
300 local_irq_save(flags);
301
302 if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
303 uid_hash_remove(up);
304 remove_user = 1;
305 spin_unlock_irqrestore(&uidhash_lock, flags);
306 } else {
307 local_irq_restore(flags);
308 }
309
310 if (!remove_user)
311 goto done;
312
313 if (up->user_ns == &init_user_ns) {
314 kobject_uevent(&up->kobj, KOBJ_REMOVE);
315 kobject_del(&up->kobj);
316 kobject_put(&up->kobj);
317 }
318
319 sched_destroy_user(up);
320 key_put(up->uid_keyring);
321 key_put(up->session_keyring);
322 kmem_cache_free(uid_cachep, up);
323
324done:
325 uids_mutex_unlock();
326}
327
328/* IRQs are disabled and uidhash_lock is held upon function entry.
329 * IRQ state (as stored in flags) is restored and uidhash_lock released
330 * upon function exit.
331 */
332static void free_user(struct user_struct *up, unsigned long flags)
333{
334 /* restore back the count */
335 atomic_inc(&up->__count);
336 spin_unlock_irqrestore(&uidhash_lock, flags);
337
338 INIT_WORK(&up->work, cleanup_user_struct);
339 schedule_work(&up->work);
340}
341
342#else /* CONFIG_USER_SCHED && CONFIG_SYSFS */
343
344int uids_sysfs_init(void) { return 0; }
345static inline int uids_user_create(struct user_struct *up) { return 0; }
346static inline void uids_mutex_lock(void) { }
347static inline void uids_mutex_unlock(void) { }
348
349/* IRQs are disabled and uidhash_lock is held upon function entry.
350 * IRQ state (as stored in flags) is restored and uidhash_lock released
351 * upon function exit.
352 */
353static void free_user(struct user_struct *up, unsigned long flags)
354{
355 uid_hash_remove(up);
356 spin_unlock_irqrestore(&uidhash_lock, flags);
357 sched_destroy_user(up);
358 key_put(up->uid_keyring);
359 key_put(up->session_keyring);
360 kmem_cache_free(uid_cachep, up);
361}
362
363#endif
364
365#if defined(CONFIG_RT_GROUP_SCHED) && defined(CONFIG_USER_SCHED)
366/*
367 * We need to check if a setuid can take place. This function should be called
368 * before successfully completing the setuid.
369 */
370int task_can_switch_user(struct user_struct *up, struct task_struct *tsk)
371{
372
373 return sched_rt_can_attach(up->tg, tsk);
374
375}
376#else
377int task_can_switch_user(struct user_struct *up, struct task_struct *tsk)
378{
379 return 1;
380}
381#endif
382
383/*
384 * Locate the user_struct for the passed UID. If found, take a ref on it. The
385 * caller must undo that ref with free_uid().
386 *
387 * If the user_struct could not be found, return NULL.
388 */
389struct user_struct *find_user(uid_t uid)
390{
391 struct user_struct *ret;
392 unsigned long flags;
393 struct user_namespace *ns = current_user_ns();
394
395 spin_lock_irqsave(&uidhash_lock, flags);
396 ret = uid_hash_find(uid, uidhashentry(ns, uid));
397 spin_unlock_irqrestore(&uidhash_lock, flags);
398 return ret;
399}
400
401void free_uid(struct user_struct *up)
402{
403 unsigned long flags;
404
405 if (!up)
406 return;
407
408 local_irq_save(flags);
409 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
410 free_user(up, flags);
411 else
412 local_irq_restore(flags);
413}
414
415struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid)
416{
417 struct hlist_head *hashent = uidhashentry(ns, uid);
418 struct user_struct *up, *new;
419
420 /* Make uid_hash_find() + uids_user_create() + uid_hash_insert()
421 * atomic.
422 */
423 uids_mutex_lock();
424
425 spin_lock_irq(&uidhash_lock);
426 up = uid_hash_find(uid, hashent);
427 spin_unlock_irq(&uidhash_lock);
428
429 if (!up) {
430 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
431 if (!new)
432 goto out_unlock;
433
434 new->uid = uid;
435 atomic_set(&new->__count, 1);
436
437 if (sched_create_user(new) < 0)
438 goto out_free_user;
439
440 new->user_ns = get_user_ns(ns);
441
442 if (uids_user_create(new))
443 goto out_destoy_sched;
444
445 /*
446 * Before adding this, check whether we raced
447 * on adding the same user already..
448 */
449 spin_lock_irq(&uidhash_lock);
450 up = uid_hash_find(uid, hashent);
451 if (up) {
452 /* This case is not possible when CONFIG_USER_SCHED
453 * is defined, since we serialize alloc_uid() using
454 * uids_mutex. Hence no need to call
455 * sched_destroy_user() or remove_user_sysfs_dir().
456 */
457 key_put(new->uid_keyring);
458 key_put(new->session_keyring);
459 kmem_cache_free(uid_cachep, new);
460 } else {
461 uid_hash_insert(new, hashent);
462 up = new;
463 }
464 spin_unlock_irq(&uidhash_lock);
465 }
466
467 uids_mutex_unlock();
468
469 return up;
470
471out_destoy_sched:
472 sched_destroy_user(new);
473 put_user_ns(new->user_ns);
474out_free_user:
475 kmem_cache_free(uid_cachep, new);
476out_unlock:
477 uids_mutex_unlock();
478 return NULL;
479}
480
481static int __init uid_cache_init(void)
482{
483 int n;
484
485 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
486 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
487
488 for(n = 0; n < UIDHASH_SZ; ++n)
489 INIT_HLIST_HEAD(init_user_ns.uidhash_table + n);
490
491 /* Insert the root user immediately (init already runs as root) */
492 spin_lock_irq(&uidhash_lock);
493 uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
494 spin_unlock_irq(&uidhash_lock);
495
496 return 0;
497}
498
499module_init(uid_cache_init);