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Source at commit cdde9cf73945d547acd3e96f9508c79e84ad0bf1 created 12 years 9 months ago. By Maarten ter Huurne, MMC: JZ4740: Added support for CPU frequency changing | |
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1 | /* Task credentials management - see Documentation/security/credentials.txt |
2 | * |
3 | * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. |
4 | * Written by David Howells (dhowells@redhat.com) |
5 | * |
6 | * This program is free software; you can redistribute it and/or |
7 | * modify it under the terms of the GNU General Public Licence |
8 | * as published by the Free Software Foundation; either version |
9 | * 2 of the Licence, or (at your option) any later version. |
10 | */ |
11 | #include <linux/export.h> |
12 | #include <linux/cred.h> |
13 | #include <linux/slab.h> |
14 | #include <linux/sched.h> |
15 | #include <linux/key.h> |
16 | #include <linux/keyctl.h> |
17 | #include <linux/init_task.h> |
18 | #include <linux/security.h> |
19 | #include <linux/binfmts.h> |
20 | #include <linux/cn_proc.h> |
21 | |
22 | #if 0 |
23 | #define kdebug(FMT, ...) \ |
24 | printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__) |
25 | #else |
26 | #define kdebug(FMT, ...) \ |
27 | no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__) |
28 | #endif |
29 | |
30 | static struct kmem_cache *cred_jar; |
31 | |
32 | /* |
33 | * The common credentials for the initial task's thread group |
34 | */ |
35 | #ifdef CONFIG_KEYS |
36 | static struct thread_group_cred init_tgcred = { |
37 | .usage = ATOMIC_INIT(2), |
38 | .tgid = 0, |
39 | .lock = __SPIN_LOCK_UNLOCKED(init_cred.tgcred.lock), |
40 | }; |
41 | #endif |
42 | |
43 | /* |
44 | * The initial credentials for the initial task |
45 | */ |
46 | struct cred init_cred = { |
47 | .usage = ATOMIC_INIT(4), |
48 | #ifdef CONFIG_DEBUG_CREDENTIALS |
49 | .subscribers = ATOMIC_INIT(2), |
50 | .magic = CRED_MAGIC, |
51 | #endif |
52 | .uid = GLOBAL_ROOT_UID, |
53 | .gid = GLOBAL_ROOT_GID, |
54 | .suid = GLOBAL_ROOT_UID, |
55 | .sgid = GLOBAL_ROOT_GID, |
56 | .euid = GLOBAL_ROOT_UID, |
57 | .egid = GLOBAL_ROOT_GID, |
58 | .fsuid = GLOBAL_ROOT_UID, |
59 | .fsgid = GLOBAL_ROOT_GID, |
60 | .securebits = SECUREBITS_DEFAULT, |
61 | .cap_inheritable = CAP_EMPTY_SET, |
62 | .cap_permitted = CAP_FULL_SET, |
63 | .cap_effective = CAP_FULL_SET, |
64 | .cap_bset = CAP_FULL_SET, |
65 | .user = INIT_USER, |
66 | .user_ns = &init_user_ns, |
67 | .group_info = &init_groups, |
68 | #ifdef CONFIG_KEYS |
69 | .tgcred = &init_tgcred, |
70 | #endif |
71 | }; |
72 | |
73 | static inline void set_cred_subscribers(struct cred *cred, int n) |
74 | { |
75 | #ifdef CONFIG_DEBUG_CREDENTIALS |
76 | atomic_set(&cred->subscribers, n); |
77 | #endif |
78 | } |
79 | |
80 | static inline int read_cred_subscribers(const struct cred *cred) |
81 | { |
82 | #ifdef CONFIG_DEBUG_CREDENTIALS |
83 | return atomic_read(&cred->subscribers); |
84 | #else |
85 | return 0; |
86 | #endif |
87 | } |
88 | |
89 | static inline void alter_cred_subscribers(const struct cred *_cred, int n) |
90 | { |
91 | #ifdef CONFIG_DEBUG_CREDENTIALS |
92 | struct cred *cred = (struct cred *) _cred; |
93 | |
94 | atomic_add(n, &cred->subscribers); |
95 | #endif |
96 | } |
97 | |
98 | /* |
99 | * Dispose of the shared task group credentials |
100 | */ |
101 | #ifdef CONFIG_KEYS |
102 | static void release_tgcred_rcu(struct rcu_head *rcu) |
103 | { |
104 | struct thread_group_cred *tgcred = |
105 | container_of(rcu, struct thread_group_cred, rcu); |
106 | |
107 | BUG_ON(atomic_read(&tgcred->usage) != 0); |
108 | |
109 | key_put(tgcred->session_keyring); |
110 | key_put(tgcred->process_keyring); |
111 | kfree(tgcred); |
112 | } |
113 | #endif |
114 | |
115 | /* |
116 | * Release a set of thread group credentials. |
117 | */ |
118 | static void release_tgcred(struct cred *cred) |
119 | { |
120 | #ifdef CONFIG_KEYS |
121 | struct thread_group_cred *tgcred = cred->tgcred; |
122 | |
123 | if (atomic_dec_and_test(&tgcred->usage)) |
124 | call_rcu(&tgcred->rcu, release_tgcred_rcu); |
125 | #endif |
126 | } |
127 | |
128 | /* |
129 | * The RCU callback to actually dispose of a set of credentials |
130 | */ |
131 | static void put_cred_rcu(struct rcu_head *rcu) |
132 | { |
133 | struct cred *cred = container_of(rcu, struct cred, rcu); |
134 | |
135 | kdebug("put_cred_rcu(%p)", cred); |
136 | |
137 | #ifdef CONFIG_DEBUG_CREDENTIALS |
138 | if (cred->magic != CRED_MAGIC_DEAD || |
139 | atomic_read(&cred->usage) != 0 || |
140 | read_cred_subscribers(cred) != 0) |
141 | panic("CRED: put_cred_rcu() sees %p with" |
142 | " mag %x, put %p, usage %d, subscr %d\n", |
143 | cred, cred->magic, cred->put_addr, |
144 | atomic_read(&cred->usage), |
145 | read_cred_subscribers(cred)); |
146 | #else |
147 | if (atomic_read(&cred->usage) != 0) |
148 | panic("CRED: put_cred_rcu() sees %p with usage %d\n", |
149 | cred, atomic_read(&cred->usage)); |
150 | #endif |
151 | |
152 | security_cred_free(cred); |
153 | key_put(cred->thread_keyring); |
154 | key_put(cred->request_key_auth); |
155 | release_tgcred(cred); |
156 | if (cred->group_info) |
157 | put_group_info(cred->group_info); |
158 | free_uid(cred->user); |
159 | put_user_ns(cred->user_ns); |
160 | kmem_cache_free(cred_jar, cred); |
161 | } |
162 | |
163 | /** |
164 | * __put_cred - Destroy a set of credentials |
165 | * @cred: The record to release |
166 | * |
167 | * Destroy a set of credentials on which no references remain. |
168 | */ |
169 | void __put_cred(struct cred *cred) |
170 | { |
171 | kdebug("__put_cred(%p{%d,%d})", cred, |
172 | atomic_read(&cred->usage), |
173 | read_cred_subscribers(cred)); |
174 | |
175 | BUG_ON(atomic_read(&cred->usage) != 0); |
176 | #ifdef CONFIG_DEBUG_CREDENTIALS |
177 | BUG_ON(read_cred_subscribers(cred) != 0); |
178 | cred->magic = CRED_MAGIC_DEAD; |
179 | cred->put_addr = __builtin_return_address(0); |
180 | #endif |
181 | BUG_ON(cred == current->cred); |
182 | BUG_ON(cred == current->real_cred); |
183 | |
184 | call_rcu(&cred->rcu, put_cred_rcu); |
185 | } |
186 | EXPORT_SYMBOL(__put_cred); |
187 | |
188 | /* |
189 | * Clean up a task's credentials when it exits |
190 | */ |
191 | void exit_creds(struct task_struct *tsk) |
192 | { |
193 | struct cred *cred; |
194 | |
195 | kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred, |
196 | atomic_read(&tsk->cred->usage), |
197 | read_cred_subscribers(tsk->cred)); |
198 | |
199 | cred = (struct cred *) tsk->real_cred; |
200 | tsk->real_cred = NULL; |
201 | validate_creds(cred); |
202 | alter_cred_subscribers(cred, -1); |
203 | put_cred(cred); |
204 | |
205 | cred = (struct cred *) tsk->cred; |
206 | tsk->cred = NULL; |
207 | validate_creds(cred); |
208 | alter_cred_subscribers(cred, -1); |
209 | put_cred(cred); |
210 | } |
211 | |
212 | /** |
213 | * get_task_cred - Get another task's objective credentials |
214 | * @task: The task to query |
215 | * |
216 | * Get the objective credentials of a task, pinning them so that they can't go |
217 | * away. Accessing a task's credentials directly is not permitted. |
218 | * |
219 | * The caller must also make sure task doesn't get deleted, either by holding a |
220 | * ref on task or by holding tasklist_lock to prevent it from being unlinked. |
221 | */ |
222 | const struct cred *get_task_cred(struct task_struct *task) |
223 | { |
224 | const struct cred *cred; |
225 | |
226 | rcu_read_lock(); |
227 | |
228 | do { |
229 | cred = __task_cred((task)); |
230 | BUG_ON(!cred); |
231 | } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage)); |
232 | |
233 | rcu_read_unlock(); |
234 | return cred; |
235 | } |
236 | |
237 | /* |
238 | * Allocate blank credentials, such that the credentials can be filled in at a |
239 | * later date without risk of ENOMEM. |
240 | */ |
241 | struct cred *cred_alloc_blank(void) |
242 | { |
243 | struct cred *new; |
244 | |
245 | new = kmem_cache_zalloc(cred_jar, GFP_KERNEL); |
246 | if (!new) |
247 | return NULL; |
248 | |
249 | #ifdef CONFIG_KEYS |
250 | new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL); |
251 | if (!new->tgcred) { |
252 | kmem_cache_free(cred_jar, new); |
253 | return NULL; |
254 | } |
255 | atomic_set(&new->tgcred->usage, 1); |
256 | #endif |
257 | |
258 | atomic_set(&new->usage, 1); |
259 | #ifdef CONFIG_DEBUG_CREDENTIALS |
260 | new->magic = CRED_MAGIC; |
261 | #endif |
262 | |
263 | if (security_cred_alloc_blank(new, GFP_KERNEL) < 0) |
264 | goto error; |
265 | |
266 | return new; |
267 | |
268 | error: |
269 | abort_creds(new); |
270 | return NULL; |
271 | } |
272 | |
273 | /** |
274 | * prepare_creds - Prepare a new set of credentials for modification |
275 | * |
276 | * Prepare a new set of task credentials for modification. A task's creds |
277 | * shouldn't generally be modified directly, therefore this function is used to |
278 | * prepare a new copy, which the caller then modifies and then commits by |
279 | * calling commit_creds(). |
280 | * |
281 | * Preparation involves making a copy of the objective creds for modification. |
282 | * |
283 | * Returns a pointer to the new creds-to-be if successful, NULL otherwise. |
284 | * |
285 | * Call commit_creds() or abort_creds() to clean up. |
286 | */ |
287 | struct cred *prepare_creds(void) |
288 | { |
289 | struct task_struct *task = current; |
290 | const struct cred *old; |
291 | struct cred *new; |
292 | |
293 | validate_process_creds(); |
294 | |
295 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); |
296 | if (!new) |
297 | return NULL; |
298 | |
299 | kdebug("prepare_creds() alloc %p", new); |
300 | |
301 | old = task->cred; |
302 | memcpy(new, old, sizeof(struct cred)); |
303 | |
304 | atomic_set(&new->usage, 1); |
305 | set_cred_subscribers(new, 0); |
306 | get_group_info(new->group_info); |
307 | get_uid(new->user); |
308 | get_user_ns(new->user_ns); |
309 | |
310 | #ifdef CONFIG_KEYS |
311 | key_get(new->thread_keyring); |
312 | key_get(new->request_key_auth); |
313 | atomic_inc(&new->tgcred->usage); |
314 | #endif |
315 | |
316 | #ifdef CONFIG_SECURITY |
317 | new->security = NULL; |
318 | #endif |
319 | |
320 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) |
321 | goto error; |
322 | validate_creds(new); |
323 | return new; |
324 | |
325 | error: |
326 | abort_creds(new); |
327 | return NULL; |
328 | } |
329 | EXPORT_SYMBOL(prepare_creds); |
330 | |
331 | /* |
332 | * Prepare credentials for current to perform an execve() |
333 | * - The caller must hold ->cred_guard_mutex |
334 | */ |
335 | struct cred *prepare_exec_creds(void) |
336 | { |
337 | struct thread_group_cred *tgcred = NULL; |
338 | struct cred *new; |
339 | |
340 | #ifdef CONFIG_KEYS |
341 | tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); |
342 | if (!tgcred) |
343 | return NULL; |
344 | #endif |
345 | |
346 | new = prepare_creds(); |
347 | if (!new) { |
348 | kfree(tgcred); |
349 | return new; |
350 | } |
351 | |
352 | #ifdef CONFIG_KEYS |
353 | /* newly exec'd tasks don't get a thread keyring */ |
354 | key_put(new->thread_keyring); |
355 | new->thread_keyring = NULL; |
356 | |
357 | /* create a new per-thread-group creds for all this set of threads to |
358 | * share */ |
359 | memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred)); |
360 | |
361 | atomic_set(&tgcred->usage, 1); |
362 | spin_lock_init(&tgcred->lock); |
363 | |
364 | /* inherit the session keyring; new process keyring */ |
365 | key_get(tgcred->session_keyring); |
366 | tgcred->process_keyring = NULL; |
367 | |
368 | release_tgcred(new); |
369 | new->tgcred = tgcred; |
370 | #endif |
371 | |
372 | return new; |
373 | } |
374 | |
375 | /* |
376 | * Copy credentials for the new process created by fork() |
377 | * |
378 | * We share if we can, but under some circumstances we have to generate a new |
379 | * set. |
380 | * |
381 | * The new process gets the current process's subjective credentials as its |
382 | * objective and subjective credentials |
383 | */ |
384 | int copy_creds(struct task_struct *p, unsigned long clone_flags) |
385 | { |
386 | #ifdef CONFIG_KEYS |
387 | struct thread_group_cred *tgcred; |
388 | #endif |
389 | struct cred *new; |
390 | int ret; |
391 | |
392 | if ( |
393 | #ifdef CONFIG_KEYS |
394 | !p->cred->thread_keyring && |
395 | #endif |
396 | clone_flags & CLONE_THREAD |
397 | ) { |
398 | p->real_cred = get_cred(p->cred); |
399 | get_cred(p->cred); |
400 | alter_cred_subscribers(p->cred, 2); |
401 | kdebug("share_creds(%p{%d,%d})", |
402 | p->cred, atomic_read(&p->cred->usage), |
403 | read_cred_subscribers(p->cred)); |
404 | atomic_inc(&p->cred->user->processes); |
405 | return 0; |
406 | } |
407 | |
408 | new = prepare_creds(); |
409 | if (!new) |
410 | return -ENOMEM; |
411 | |
412 | if (clone_flags & CLONE_NEWUSER) { |
413 | ret = create_user_ns(new); |
414 | if (ret < 0) |
415 | goto error_put; |
416 | } |
417 | |
418 | #ifdef CONFIG_KEYS |
419 | /* new threads get their own thread keyrings if their parent already |
420 | * had one */ |
421 | if (new->thread_keyring) { |
422 | key_put(new->thread_keyring); |
423 | new->thread_keyring = NULL; |
424 | if (clone_flags & CLONE_THREAD) |
425 | install_thread_keyring_to_cred(new); |
426 | } |
427 | |
428 | /* we share the process and session keyrings between all the threads in |
429 | * a process - this is slightly icky as we violate COW credentials a |
430 | * bit */ |
431 | if (!(clone_flags & CLONE_THREAD)) { |
432 | tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); |
433 | if (!tgcred) { |
434 | ret = -ENOMEM; |
435 | goto error_put; |
436 | } |
437 | atomic_set(&tgcred->usage, 1); |
438 | spin_lock_init(&tgcred->lock); |
439 | tgcred->process_keyring = NULL; |
440 | tgcred->session_keyring = key_get(new->tgcred->session_keyring); |
441 | |
442 | release_tgcred(new); |
443 | new->tgcred = tgcred; |
444 | } |
445 | #endif |
446 | |
447 | atomic_inc(&new->user->processes); |
448 | p->cred = p->real_cred = get_cred(new); |
449 | alter_cred_subscribers(new, 2); |
450 | validate_creds(new); |
451 | return 0; |
452 | |
453 | error_put: |
454 | put_cred(new); |
455 | return ret; |
456 | } |
457 | |
458 | /** |
459 | * commit_creds - Install new credentials upon the current task |
460 | * @new: The credentials to be assigned |
461 | * |
462 | * Install a new set of credentials to the current task, using RCU to replace |
463 | * the old set. Both the objective and the subjective credentials pointers are |
464 | * updated. This function may not be called if the subjective credentials are |
465 | * in an overridden state. |
466 | * |
467 | * This function eats the caller's reference to the new credentials. |
468 | * |
469 | * Always returns 0 thus allowing this function to be tail-called at the end |
470 | * of, say, sys_setgid(). |
471 | */ |
472 | int commit_creds(struct cred *new) |
473 | { |
474 | struct task_struct *task = current; |
475 | const struct cred *old = task->real_cred; |
476 | |
477 | kdebug("commit_creds(%p{%d,%d})", new, |
478 | atomic_read(&new->usage), |
479 | read_cred_subscribers(new)); |
480 | |
481 | BUG_ON(task->cred != old); |
482 | #ifdef CONFIG_DEBUG_CREDENTIALS |
483 | BUG_ON(read_cred_subscribers(old) < 2); |
484 | validate_creds(old); |
485 | validate_creds(new); |
486 | #endif |
487 | BUG_ON(atomic_read(&new->usage) < 1); |
488 | |
489 | get_cred(new); /* we will require a ref for the subj creds too */ |
490 | |
491 | /* dumpability changes */ |
492 | if (!uid_eq(old->euid, new->euid) || |
493 | !gid_eq(old->egid, new->egid) || |
494 | !uid_eq(old->fsuid, new->fsuid) || |
495 | !gid_eq(old->fsgid, new->fsgid) || |
496 | !cap_issubset(new->cap_permitted, old->cap_permitted)) { |
497 | if (task->mm) |
498 | set_dumpable(task->mm, suid_dumpable); |
499 | task->pdeath_signal = 0; |
500 | smp_wmb(); |
501 | } |
502 | |
503 | /* alter the thread keyring */ |
504 | if (!uid_eq(new->fsuid, old->fsuid)) |
505 | key_fsuid_changed(task); |
506 | if (!gid_eq(new->fsgid, old->fsgid)) |
507 | key_fsgid_changed(task); |
508 | |
509 | /* do it |
510 | * RLIMIT_NPROC limits on user->processes have already been checked |
511 | * in set_user(). |
512 | */ |
513 | alter_cred_subscribers(new, 2); |
514 | if (new->user != old->user) |
515 | atomic_inc(&new->user->processes); |
516 | rcu_assign_pointer(task->real_cred, new); |
517 | rcu_assign_pointer(task->cred, new); |
518 | if (new->user != old->user) |
519 | atomic_dec(&old->user->processes); |
520 | alter_cred_subscribers(old, -2); |
521 | |
522 | /* send notifications */ |
523 | if (!uid_eq(new->uid, old->uid) || |
524 | !uid_eq(new->euid, old->euid) || |
525 | !uid_eq(new->suid, old->suid) || |
526 | !uid_eq(new->fsuid, old->fsuid)) |
527 | proc_id_connector(task, PROC_EVENT_UID); |
528 | |
529 | if (!gid_eq(new->gid, old->gid) || |
530 | !gid_eq(new->egid, old->egid) || |
531 | !gid_eq(new->sgid, old->sgid) || |
532 | !gid_eq(new->fsgid, old->fsgid)) |
533 | proc_id_connector(task, PROC_EVENT_GID); |
534 | |
535 | /* release the old obj and subj refs both */ |
536 | put_cred(old); |
537 | put_cred(old); |
538 | return 0; |
539 | } |
540 | EXPORT_SYMBOL(commit_creds); |
541 | |
542 | /** |
543 | * abort_creds - Discard a set of credentials and unlock the current task |
544 | * @new: The credentials that were going to be applied |
545 | * |
546 | * Discard a set of credentials that were under construction and unlock the |
547 | * current task. |
548 | */ |
549 | void abort_creds(struct cred *new) |
550 | { |
551 | kdebug("abort_creds(%p{%d,%d})", new, |
552 | atomic_read(&new->usage), |
553 | read_cred_subscribers(new)); |
554 | |
555 | #ifdef CONFIG_DEBUG_CREDENTIALS |
556 | BUG_ON(read_cred_subscribers(new) != 0); |
557 | #endif |
558 | BUG_ON(atomic_read(&new->usage) < 1); |
559 | put_cred(new); |
560 | } |
561 | EXPORT_SYMBOL(abort_creds); |
562 | |
563 | /** |
564 | * override_creds - Override the current process's subjective credentials |
565 | * @new: The credentials to be assigned |
566 | * |
567 | * Install a set of temporary override subjective credentials on the current |
568 | * process, returning the old set for later reversion. |
569 | */ |
570 | const struct cred *override_creds(const struct cred *new) |
571 | { |
572 | const struct cred *old = current->cred; |
573 | |
574 | kdebug("override_creds(%p{%d,%d})", new, |
575 | atomic_read(&new->usage), |
576 | read_cred_subscribers(new)); |
577 | |
578 | validate_creds(old); |
579 | validate_creds(new); |
580 | get_cred(new); |
581 | alter_cred_subscribers(new, 1); |
582 | rcu_assign_pointer(current->cred, new); |
583 | alter_cred_subscribers(old, -1); |
584 | |
585 | kdebug("override_creds() = %p{%d,%d}", old, |
586 | atomic_read(&old->usage), |
587 | read_cred_subscribers(old)); |
588 | return old; |
589 | } |
590 | EXPORT_SYMBOL(override_creds); |
591 | |
592 | /** |
593 | * revert_creds - Revert a temporary subjective credentials override |
594 | * @old: The credentials to be restored |
595 | * |
596 | * Revert a temporary set of override subjective credentials to an old set, |
597 | * discarding the override set. |
598 | */ |
599 | void revert_creds(const struct cred *old) |
600 | { |
601 | const struct cred *override = current->cred; |
602 | |
603 | kdebug("revert_creds(%p{%d,%d})", old, |
604 | atomic_read(&old->usage), |
605 | read_cred_subscribers(old)); |
606 | |
607 | validate_creds(old); |
608 | validate_creds(override); |
609 | alter_cred_subscribers(old, 1); |
610 | rcu_assign_pointer(current->cred, old); |
611 | alter_cred_subscribers(override, -1); |
612 | put_cred(override); |
613 | } |
614 | EXPORT_SYMBOL(revert_creds); |
615 | |
616 | /* |
617 | * initialise the credentials stuff |
618 | */ |
619 | void __init cred_init(void) |
620 | { |
621 | /* allocate a slab in which we can store credentials */ |
622 | cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), |
623 | 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); |
624 | } |
625 | |
626 | /** |
627 | * prepare_kernel_cred - Prepare a set of credentials for a kernel service |
628 | * @daemon: A userspace daemon to be used as a reference |
629 | * |
630 | * Prepare a set of credentials for a kernel service. This can then be used to |
631 | * override a task's own credentials so that work can be done on behalf of that |
632 | * task that requires a different subjective context. |
633 | * |
634 | * @daemon is used to provide a base for the security record, but can be NULL. |
635 | * If @daemon is supplied, then the security data will be derived from that; |
636 | * otherwise they'll be set to 0 and no groups, full capabilities and no keys. |
637 | * |
638 | * The caller may change these controls afterwards if desired. |
639 | * |
640 | * Returns the new credentials or NULL if out of memory. |
641 | * |
642 | * Does not take, and does not return holding current->cred_replace_mutex. |
643 | */ |
644 | struct cred *prepare_kernel_cred(struct task_struct *daemon) |
645 | { |
646 | #ifdef CONFIG_KEYS |
647 | struct thread_group_cred *tgcred; |
648 | #endif |
649 | const struct cred *old; |
650 | struct cred *new; |
651 | |
652 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); |
653 | if (!new) |
654 | return NULL; |
655 | |
656 | #ifdef CONFIG_KEYS |
657 | tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); |
658 | if (!tgcred) { |
659 | kmem_cache_free(cred_jar, new); |
660 | return NULL; |
661 | } |
662 | #endif |
663 | |
664 | kdebug("prepare_kernel_cred() alloc %p", new); |
665 | |
666 | if (daemon) |
667 | old = get_task_cred(daemon); |
668 | else |
669 | old = get_cred(&init_cred); |
670 | |
671 | validate_creds(old); |
672 | |
673 | *new = *old; |
674 | atomic_set(&new->usage, 1); |
675 | set_cred_subscribers(new, 0); |
676 | get_uid(new->user); |
677 | get_user_ns(new->user_ns); |
678 | get_group_info(new->group_info); |
679 | |
680 | #ifdef CONFIG_KEYS |
681 | atomic_set(&tgcred->usage, 1); |
682 | spin_lock_init(&tgcred->lock); |
683 | tgcred->process_keyring = NULL; |
684 | tgcred->session_keyring = NULL; |
685 | new->tgcred = tgcred; |
686 | new->request_key_auth = NULL; |
687 | new->thread_keyring = NULL; |
688 | new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; |
689 | #endif |
690 | |
691 | #ifdef CONFIG_SECURITY |
692 | new->security = NULL; |
693 | #endif |
694 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) |
695 | goto error; |
696 | |
697 | put_cred(old); |
698 | validate_creds(new); |
699 | return new; |
700 | |
701 | error: |
702 | put_cred(new); |
703 | put_cred(old); |
704 | return NULL; |
705 | } |
706 | EXPORT_SYMBOL(prepare_kernel_cred); |
707 | |
708 | /** |
709 | * set_security_override - Set the security ID in a set of credentials |
710 | * @new: The credentials to alter |
711 | * @secid: The LSM security ID to set |
712 | * |
713 | * Set the LSM security ID in a set of credentials so that the subjective |
714 | * security is overridden when an alternative set of credentials is used. |
715 | */ |
716 | int set_security_override(struct cred *new, u32 secid) |
717 | { |
718 | return security_kernel_act_as(new, secid); |
719 | } |
720 | EXPORT_SYMBOL(set_security_override); |
721 | |
722 | /** |
723 | * set_security_override_from_ctx - Set the security ID in a set of credentials |
724 | * @new: The credentials to alter |
725 | * @secctx: The LSM security context to generate the security ID from. |
726 | * |
727 | * Set the LSM security ID in a set of credentials so that the subjective |
728 | * security is overridden when an alternative set of credentials is used. The |
729 | * security ID is specified in string form as a security context to be |
730 | * interpreted by the LSM. |
731 | */ |
732 | int set_security_override_from_ctx(struct cred *new, const char *secctx) |
733 | { |
734 | u32 secid; |
735 | int ret; |
736 | |
737 | ret = security_secctx_to_secid(secctx, strlen(secctx), &secid); |
738 | if (ret < 0) |
739 | return ret; |
740 | |
741 | return set_security_override(new, secid); |
742 | } |
743 | EXPORT_SYMBOL(set_security_override_from_ctx); |
744 | |
745 | /** |
746 | * set_create_files_as - Set the LSM file create context in a set of credentials |
747 | * @new: The credentials to alter |
748 | * @inode: The inode to take the context from |
749 | * |
750 | * Change the LSM file creation context in a set of credentials to be the same |
751 | * as the object context of the specified inode, so that the new inodes have |
752 | * the same MAC context as that inode. |
753 | */ |
754 | int set_create_files_as(struct cred *new, struct inode *inode) |
755 | { |
756 | new->fsuid = inode->i_uid; |
757 | new->fsgid = inode->i_gid; |
758 | return security_kernel_create_files_as(new, inode); |
759 | } |
760 | EXPORT_SYMBOL(set_create_files_as); |
761 | |
762 | #ifdef CONFIG_DEBUG_CREDENTIALS |
763 | |
764 | bool creds_are_invalid(const struct cred *cred) |
765 | { |
766 | if (cred->magic != CRED_MAGIC) |
767 | return true; |
768 | #ifdef CONFIG_SECURITY_SELINUX |
769 | /* |
770 | * cred->security == NULL if security_cred_alloc_blank() or |
771 | * security_prepare_creds() returned an error. |
772 | */ |
773 | if (selinux_is_enabled() && cred->security) { |
774 | if ((unsigned long) cred->security < PAGE_SIZE) |
775 | return true; |
776 | if ((*(u32 *)cred->security & 0xffffff00) == |
777 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)) |
778 | return true; |
779 | } |
780 | #endif |
781 | return false; |
782 | } |
783 | EXPORT_SYMBOL(creds_are_invalid); |
784 | |
785 | /* |
786 | * dump invalid credentials |
787 | */ |
788 | static void dump_invalid_creds(const struct cred *cred, const char *label, |
789 | const struct task_struct *tsk) |
790 | { |
791 | printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n", |
792 | label, cred, |
793 | cred == &init_cred ? "[init]" : "", |
794 | cred == tsk->real_cred ? "[real]" : "", |
795 | cred == tsk->cred ? "[eff]" : ""); |
796 | printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n", |
797 | cred->magic, cred->put_addr); |
798 | printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n", |
799 | atomic_read(&cred->usage), |
800 | read_cred_subscribers(cred)); |
801 | printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n", |
802 | cred->uid, cred->euid, cred->suid, cred->fsuid); |
803 | printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n", |
804 | cred->gid, cred->egid, cred->sgid, cred->fsgid); |
805 | #ifdef CONFIG_SECURITY |
806 | printk(KERN_ERR "CRED: ->security is %p\n", cred->security); |
807 | if ((unsigned long) cred->security >= PAGE_SIZE && |
808 | (((unsigned long) cred->security & 0xffffff00) != |
809 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))) |
810 | printk(KERN_ERR "CRED: ->security {%x, %x}\n", |
811 | ((u32*)cred->security)[0], |
812 | ((u32*)cred->security)[1]); |
813 | #endif |
814 | } |
815 | |
816 | /* |
817 | * report use of invalid credentials |
818 | */ |
819 | void __invalid_creds(const struct cred *cred, const char *file, unsigned line) |
820 | { |
821 | printk(KERN_ERR "CRED: Invalid credentials\n"); |
822 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); |
823 | dump_invalid_creds(cred, "Specified", current); |
824 | BUG(); |
825 | } |
826 | EXPORT_SYMBOL(__invalid_creds); |
827 | |
828 | /* |
829 | * check the credentials on a process |
830 | */ |
831 | void __validate_process_creds(struct task_struct *tsk, |
832 | const char *file, unsigned line) |
833 | { |
834 | if (tsk->cred == tsk->real_cred) { |
835 | if (unlikely(read_cred_subscribers(tsk->cred) < 2 || |
836 | creds_are_invalid(tsk->cred))) |
837 | goto invalid_creds; |
838 | } else { |
839 | if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 || |
840 | read_cred_subscribers(tsk->cred) < 1 || |
841 | creds_are_invalid(tsk->real_cred) || |
842 | creds_are_invalid(tsk->cred))) |
843 | goto invalid_creds; |
844 | } |
845 | return; |
846 | |
847 | invalid_creds: |
848 | printk(KERN_ERR "CRED: Invalid process credentials\n"); |
849 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); |
850 | |
851 | dump_invalid_creds(tsk->real_cred, "Real", tsk); |
852 | if (tsk->cred != tsk->real_cred) |
853 | dump_invalid_creds(tsk->cred, "Effective", tsk); |
854 | else |
855 | printk(KERN_ERR "CRED: Effective creds == Real creds\n"); |
856 | BUG(); |
857 | } |
858 | EXPORT_SYMBOL(__validate_process_creds); |
859 | |
860 | /* |
861 | * check creds for do_exit() |
862 | */ |
863 | void validate_creds_for_do_exit(struct task_struct *tsk) |
864 | { |
865 | kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})", |
866 | tsk->real_cred, tsk->cred, |
867 | atomic_read(&tsk->cred->usage), |
868 | read_cred_subscribers(tsk->cred)); |
869 | |
870 | __validate_process_creds(tsk, __FILE__, __LINE__); |
871 | } |
872 | |
873 | #endif /* CONFIG_DEBUG_CREDENTIALS */ |
874 |
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