projects/linux·blob v2.6.29-rc1 · refs

482 lines · 11.5 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(1),
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}
76
77static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
78{
79 struct user_struct *user;
80 struct hlist_node *h;
81
82 hlist_for_each_entry(user, h, hashent, uidhash_node) {
83 if (user->uid == uid) {
84 atomic_inc(&user->__count);
85 return user;
86 }
87 }
88
89 return NULL;
90}
91
92#ifdef CONFIG_USER_SCHED
93
94static void sched_destroy_user(struct user_struct *up)
95{
96 sched_destroy_group(up->tg);
97}
98
99static int sched_create_user(struct user_struct *up)
100{
101 int rc = 0;
102
103 up->tg = sched_create_group(&root_task_group);
104 if (IS_ERR(up->tg))
105 rc = -ENOMEM;
106
107 set_tg_uid(up);
108
109 return rc;
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; }
116
117#endif /* CONFIG_USER_SCHED */
118
119#if defined(CONFIG_USER_SCHED) && defined(CONFIG_SYSFS)
120
121static struct kset *uids_kset; /* represents the /sys/kernel/uids/ directory */
122static DEFINE_MUTEX(uids_mutex);
123
124static inline void uids_mutex_lock(void)
125{
126 mutex_lock(&uids_mutex);
127}
128
129static inline void uids_mutex_unlock(void)
130{
131 mutex_unlock(&uids_mutex);
132}
133
134/* uid directory attributes */
135#ifdef CONFIG_FAIR_GROUP_SCHED
136static ssize_t cpu_shares_show(struct kobject *kobj,
137 struct kobj_attribute *attr,
138 char *buf)
139{
140 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
141
142 return sprintf(buf, "%lu\n", sched_group_shares(up->tg));
143}
144
145static ssize_t cpu_shares_store(struct kobject *kobj,
146 struct kobj_attribute *attr,
147 const char *buf, size_t size)
148{
149 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
150 unsigned long shares;
151 int rc;
152
153 sscanf(buf, "%lu", &shares);
154
155 rc = sched_group_set_shares(up->tg, shares);
156
157 return (rc ? rc : size);
158}
159
160static struct kobj_attribute cpu_share_attr =
161 __ATTR(cpu_share, 0644, cpu_shares_show, cpu_shares_store);
162#endif
163
164#ifdef CONFIG_RT_GROUP_SCHED
165static ssize_t cpu_rt_runtime_show(struct kobject *kobj,
166 struct kobj_attribute *attr,
167 char *buf)
168{
169 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
170
171 return sprintf(buf, "%ld\n", sched_group_rt_runtime(up->tg));
172}
173
174static ssize_t cpu_rt_runtime_store(struct kobject *kobj,
175 struct kobj_attribute *attr,
176 const char *buf, size_t size)
177{
178 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
179 unsigned long rt_runtime;
180 int rc;
181
182 sscanf(buf, "%ld", &rt_runtime);
183
184 rc = sched_group_set_rt_runtime(up->tg, rt_runtime);
185
186 return (rc ? rc : size);
187}
188
189static struct kobj_attribute cpu_rt_runtime_attr =
190 __ATTR(cpu_rt_runtime, 0644, cpu_rt_runtime_show, cpu_rt_runtime_store);
191
192static ssize_t cpu_rt_period_show(struct kobject *kobj,
193 struct kobj_attribute *attr,
194 char *buf)
195{
196 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
197
198 return sprintf(buf, "%lu\n", sched_group_rt_period(up->tg));
199}
200
201static ssize_t cpu_rt_period_store(struct kobject *kobj,
202 struct kobj_attribute *attr,
203 const char *buf, size_t size)
204{
205 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
206 unsigned long rt_period;
207 int rc;
208
209 sscanf(buf, "%lu", &rt_period);
210
211 rc = sched_group_set_rt_period(up->tg, rt_period);
212
213 return (rc ? rc : size);
214}
215
216static struct kobj_attribute cpu_rt_period_attr =
217 __ATTR(cpu_rt_period, 0644, cpu_rt_period_show, cpu_rt_period_store);
218#endif
219
220/* default attributes per uid directory */
221static struct attribute *uids_attributes[] = {
222#ifdef CONFIG_FAIR_GROUP_SCHED
223 &cpu_share_attr.attr,
224#endif
225#ifdef CONFIG_RT_GROUP_SCHED
226 &cpu_rt_runtime_attr.attr,
227 &cpu_rt_period_attr.attr,
228#endif
229 NULL
230};
231
232/* the lifetime of user_struct is not managed by the core (now) */
233static void uids_release(struct kobject *kobj)
234{
235 return;
236}
237
238static struct kobj_type uids_ktype = {
239 .sysfs_ops = &kobj_sysfs_ops,
240 .default_attrs = uids_attributes,
241 .release = uids_release,
242};
243
244/*
245 * Create /sys/kernel/uids/<uid>/cpu_share file for this user
246 * We do not create this file for users in a user namespace (until
247 * sysfs tagging is implemented).
248 *
249 * See Documentation/scheduler/sched-design-CFS.txt for ramifications.
250 */
251static int uids_user_create(struct user_struct *up)
252{
253 struct kobject *kobj = &up->kobj;
254 int error;
255
256 memset(kobj, 0, sizeof(struct kobject));
257 if (up->user_ns != &init_user_ns)
258 return 0;
259 kobj->kset = uids_kset;
260 error = kobject_init_and_add(kobj, &uids_ktype, NULL, "%d", up->uid);
261 if (error) {
262 kobject_put(kobj);
263 goto done;
264 }
265
266 kobject_uevent(kobj, KOBJ_ADD);
267done:
268 return error;
269}
270
271/* create these entries in sysfs:
272 * "/sys/kernel/uids" directory
273 * "/sys/kernel/uids/0" directory (for root user)
274 * "/sys/kernel/uids/0/cpu_share" file (for root user)
275 */
276int __init uids_sysfs_init(void)
277{
278 uids_kset = kset_create_and_add("uids", NULL, kernel_kobj);
279 if (!uids_kset)
280 return -ENOMEM;
281
282 return uids_user_create(&root_user);
283}
284
285/* work function to remove sysfs directory for a user and free up
286 * corresponding structures.
287 */
288static void remove_user_sysfs_dir(struct work_struct *w)
289{
290 struct user_struct *up = container_of(w, struct user_struct, work);
291 unsigned long flags;
292 int remove_user = 0;
293
294 if (up->user_ns != &init_user_ns)
295 return;
296 /* Make uid_hash_remove() + sysfs_remove_file() + kobject_del()
297 * atomic.
298 */
299 uids_mutex_lock();
300
301 local_irq_save(flags);
302
303 if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
304 uid_hash_remove(up);
305 remove_user = 1;
306 spin_unlock_irqrestore(&uidhash_lock, flags);
307 } else {
308 local_irq_restore(flags);
309 }
310
311 if (!remove_user)
312 goto done;
313
314 kobject_uevent(&up->kobj, KOBJ_REMOVE);
315 kobject_del(&up->kobj);
316 kobject_put(&up->kobj);
317
318 sched_destroy_user(up);
319 key_put(up->uid_keyring);
320 key_put(up->session_keyring);
321 kmem_cache_free(uid_cachep, up);
322
323done:
324 uids_mutex_unlock();
325}
326
327/* IRQs are disabled and uidhash_lock is held upon function entry.
328 * IRQ state (as stored in flags) is restored and uidhash_lock released
329 * upon function exit.
330 */
331static void free_user(struct user_struct *up, unsigned long flags)
332{
333 /* restore back the count */
334 atomic_inc(&up->__count);
335 spin_unlock_irqrestore(&uidhash_lock, flags);
336
337 put_user_ns(up->user_ns);
338 INIT_WORK(&up->work, remove_user_sysfs_dir);
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 put_user_ns(up->user_ns);
361 kmem_cache_free(uid_cachep, up);
362}
363
364#endif
365
366/*
367 * Locate the user_struct for the passed UID. If found, take a ref on it. The
368 * caller must undo that ref with free_uid().
369 *
370 * If the user_struct could not be found, return NULL.
371 */
372struct user_struct *find_user(uid_t uid)
373{
374 struct user_struct *ret;
375 unsigned long flags;
376 struct user_namespace *ns = current_user_ns();
377
378 spin_lock_irqsave(&uidhash_lock, flags);
379 ret = uid_hash_find(uid, uidhashentry(ns, uid));
380 spin_unlock_irqrestore(&uidhash_lock, flags);
381 return ret;
382}
383
384void free_uid(struct user_struct *up)
385{
386 unsigned long flags;
387
388 if (!up)
389 return;
390
391 local_irq_save(flags);
392 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
393 free_user(up, flags);
394 else
395 local_irq_restore(flags);
396}
397
398struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid)
399{
400 struct hlist_head *hashent = uidhashentry(ns, uid);
401 struct user_struct *up, *new;
402
403 /* Make uid_hash_find() + uids_user_create() + uid_hash_insert()
404 * atomic.
405 */
406 uids_mutex_lock();
407
408 spin_lock_irq(&uidhash_lock);
409 up = uid_hash_find(uid, hashent);
410 spin_unlock_irq(&uidhash_lock);
411
412 if (!up) {
413 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
414 if (!new)
415 goto out_unlock;
416
417 new->uid = uid;
418 atomic_set(&new->__count, 1);
419
420 if (sched_create_user(new) < 0)
421 goto out_free_user;
422
423 new->user_ns = get_user_ns(ns);
424
425 if (uids_user_create(new))
426 goto out_destoy_sched;
427
428 /*
429 * Before adding this, check whether we raced
430 * on adding the same user already..
431 */
432 spin_lock_irq(&uidhash_lock);
433 up = uid_hash_find(uid, hashent);
434 if (up) {
435 /* This case is not possible when CONFIG_USER_SCHED
436 * is defined, since we serialize alloc_uid() using
437 * uids_mutex. Hence no need to call
438 * sched_destroy_user() or remove_user_sysfs_dir().
439 */
440 key_put(new->uid_keyring);
441 key_put(new->session_keyring);
442 kmem_cache_free(uid_cachep, new);
443 } else {
444 uid_hash_insert(new, hashent);
445 up = new;
446 }
447 spin_unlock_irq(&uidhash_lock);
448 }
449
450 uids_mutex_unlock();
451
452 return up;
453
454out_destoy_sched:
455 sched_destroy_user(new);
456 put_user_ns(new->user_ns);
457out_free_user:
458 kmem_cache_free(uid_cachep, new);
459out_unlock:
460 uids_mutex_unlock();
461 return NULL;
462}
463
464static int __init uid_cache_init(void)
465{
466 int n;
467
468 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
469 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
470
471 for(n = 0; n < UIDHASH_SZ; ++n)
472 INIT_HLIST_HEAD(init_user_ns.uidhash_table + n);
473
474 /* Insert the root user immediately (init already runs as root) */
475 spin_lock_irq(&uidhash_lock);
476 uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
477 spin_unlock_irq(&uidhash_lock);
478
479 return 0;
480}
481
482module_init(uid_cache_init);