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1 | /* Task credentials management - see Documentation/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/module.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/cn_proc.h> |
20 | #include "cred-internals.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 | static inline __attribute__((format(printf, 1, 2))) |
27 | void no_printk(const char *fmt, ...) |
28 | { |
29 | } |
30 | #define kdebug(FMT, ...) \ |
31 | no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__) |
32 | #endif |
33 | |
34 | static struct kmem_cache *cred_jar; |
35 | |
36 | /* |
37 | * The common credentials for the initial task's thread group |
38 | */ |
39 | #ifdef CONFIG_KEYS |
40 | static struct thread_group_cred init_tgcred = { |
41 | .usage = ATOMIC_INIT(2), |
42 | .tgid = 0, |
43 | .lock = SPIN_LOCK_UNLOCKED, |
44 | }; |
45 | #endif |
46 | |
47 | /* |
48 | * The initial credentials for the initial task |
49 | */ |
50 | struct cred init_cred = { |
51 | .usage = ATOMIC_INIT(4), |
52 | #ifdef CONFIG_DEBUG_CREDENTIALS |
53 | .subscribers = ATOMIC_INIT(2), |
54 | .magic = CRED_MAGIC, |
55 | #endif |
56 | .securebits = SECUREBITS_DEFAULT, |
57 | .cap_inheritable = CAP_INIT_INH_SET, |
58 | .cap_permitted = CAP_FULL_SET, |
59 | .cap_effective = CAP_INIT_EFF_SET, |
60 | .cap_bset = CAP_INIT_BSET, |
61 | .user = INIT_USER, |
62 | .group_info = &init_groups, |
63 | #ifdef CONFIG_KEYS |
64 | .tgcred = &init_tgcred, |
65 | #endif |
66 | }; |
67 | |
68 | static inline void set_cred_subscribers(struct cred *cred, int n) |
69 | { |
70 | #ifdef CONFIG_DEBUG_CREDENTIALS |
71 | atomic_set(&cred->subscribers, n); |
72 | #endif |
73 | } |
74 | |
75 | static inline int read_cred_subscribers(const struct cred *cred) |
76 | { |
77 | #ifdef CONFIG_DEBUG_CREDENTIALS |
78 | return atomic_read(&cred->subscribers); |
79 | #else |
80 | return 0; |
81 | #endif |
82 | } |
83 | |
84 | static inline void alter_cred_subscribers(const struct cred *_cred, int n) |
85 | { |
86 | #ifdef CONFIG_DEBUG_CREDENTIALS |
87 | struct cred *cred = (struct cred *) _cred; |
88 | |
89 | atomic_add(n, &cred->subscribers); |
90 | #endif |
91 | } |
92 | |
93 | /* |
94 | * Dispose of the shared task group credentials |
95 | */ |
96 | #ifdef CONFIG_KEYS |
97 | static void release_tgcred_rcu(struct rcu_head *rcu) |
98 | { |
99 | struct thread_group_cred *tgcred = |
100 | container_of(rcu, struct thread_group_cred, rcu); |
101 | |
102 | BUG_ON(atomic_read(&tgcred->usage) != 0); |
103 | |
104 | key_put(tgcred->session_keyring); |
105 | key_put(tgcred->process_keyring); |
106 | kfree(tgcred); |
107 | } |
108 | #endif |
109 | |
110 | /* |
111 | * Release a set of thread group credentials. |
112 | */ |
113 | static void release_tgcred(struct cred *cred) |
114 | { |
115 | #ifdef CONFIG_KEYS |
116 | struct thread_group_cred *tgcred = cred->tgcred; |
117 | |
118 | if (atomic_dec_and_test(&tgcred->usage)) |
119 | call_rcu(&tgcred->rcu, release_tgcred_rcu); |
120 | #endif |
121 | } |
122 | |
123 | /* |
124 | * The RCU callback to actually dispose of a set of credentials |
125 | */ |
126 | static void put_cred_rcu(struct rcu_head *rcu) |
127 | { |
128 | struct cred *cred = container_of(rcu, struct cred, rcu); |
129 | |
130 | kdebug("put_cred_rcu(%p)", cred); |
131 | |
132 | #ifdef CONFIG_DEBUG_CREDENTIALS |
133 | if (cred->magic != CRED_MAGIC_DEAD || |
134 | atomic_read(&cred->usage) != 0 || |
135 | read_cred_subscribers(cred) != 0) |
136 | panic("CRED: put_cred_rcu() sees %p with" |
137 | " mag %x, put %p, usage %d, subscr %d\n", |
138 | cred, cred->magic, cred->put_addr, |
139 | atomic_read(&cred->usage), |
140 | read_cred_subscribers(cred)); |
141 | #else |
142 | if (atomic_read(&cred->usage) != 0) |
143 | panic("CRED: put_cred_rcu() sees %p with usage %d\n", |
144 | cred, atomic_read(&cred->usage)); |
145 | #endif |
146 | |
147 | security_cred_free(cred); |
148 | key_put(cred->thread_keyring); |
149 | key_put(cred->request_key_auth); |
150 | release_tgcred(cred); |
151 | if (cred->group_info) |
152 | put_group_info(cred->group_info); |
153 | free_uid(cred->user); |
154 | kmem_cache_free(cred_jar, cred); |
155 | } |
156 | |
157 | /** |
158 | * __put_cred - Destroy a set of credentials |
159 | * @cred: The record to release |
160 | * |
161 | * Destroy a set of credentials on which no references remain. |
162 | */ |
163 | void __put_cred(struct cred *cred) |
164 | { |
165 | kdebug("__put_cred(%p{%d,%d})", cred, |
166 | atomic_read(&cred->usage), |
167 | read_cred_subscribers(cred)); |
168 | |
169 | BUG_ON(atomic_read(&cred->usage) != 0); |
170 | #ifdef CONFIG_DEBUG_CREDENTIALS |
171 | BUG_ON(read_cred_subscribers(cred) != 0); |
172 | cred->magic = CRED_MAGIC_DEAD; |
173 | cred->put_addr = __builtin_return_address(0); |
174 | #endif |
175 | BUG_ON(cred == current->cred); |
176 | BUG_ON(cred == current->real_cred); |
177 | |
178 | call_rcu(&cred->rcu, put_cred_rcu); |
179 | } |
180 | EXPORT_SYMBOL(__put_cred); |
181 | |
182 | /* |
183 | * Clean up a task's credentials when it exits |
184 | */ |
185 | void exit_creds(struct task_struct *tsk) |
186 | { |
187 | struct cred *cred; |
188 | |
189 | kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred, |
190 | atomic_read(&tsk->cred->usage), |
191 | read_cred_subscribers(tsk->cred)); |
192 | |
193 | cred = (struct cred *) tsk->real_cred; |
194 | tsk->real_cred = NULL; |
195 | validate_creds(cred); |
196 | alter_cred_subscribers(cred, -1); |
197 | put_cred(cred); |
198 | |
199 | cred = (struct cred *) tsk->cred; |
200 | tsk->cred = NULL; |
201 | validate_creds(cred); |
202 | alter_cred_subscribers(cred, -1); |
203 | put_cred(cred); |
204 | |
205 | cred = (struct cred *) tsk->replacement_session_keyring; |
206 | if (cred) { |
207 | tsk->replacement_session_keyring = NULL; |
208 | validate_creds(cred); |
209 | put_cred(cred); |
210 | } |
211 | } |
212 | |
213 | /* |
214 | * Allocate blank credentials, such that the credentials can be filled in at a |
215 | * later date without risk of ENOMEM. |
216 | */ |
217 | struct cred *cred_alloc_blank(void) |
218 | { |
219 | struct cred *new; |
220 | |
221 | new = kmem_cache_zalloc(cred_jar, GFP_KERNEL); |
222 | if (!new) |
223 | return NULL; |
224 | |
225 | #ifdef CONFIG_KEYS |
226 | new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL); |
227 | if (!new->tgcred) { |
228 | kmem_cache_free(cred_jar, new); |
229 | return NULL; |
230 | } |
231 | atomic_set(&new->tgcred->usage, 1); |
232 | #endif |
233 | |
234 | atomic_set(&new->usage, 1); |
235 | |
236 | if (security_cred_alloc_blank(new, GFP_KERNEL) < 0) |
237 | goto error; |
238 | |
239 | #ifdef CONFIG_DEBUG_CREDENTIALS |
240 | new->magic = CRED_MAGIC; |
241 | #endif |
242 | return new; |
243 | |
244 | error: |
245 | abort_creds(new); |
246 | return NULL; |
247 | } |
248 | |
249 | /** |
250 | * prepare_creds - Prepare a new set of credentials for modification |
251 | * |
252 | * Prepare a new set of task credentials for modification. A task's creds |
253 | * shouldn't generally be modified directly, therefore this function is used to |
254 | * prepare a new copy, which the caller then modifies and then commits by |
255 | * calling commit_creds(). |
256 | * |
257 | * Preparation involves making a copy of the objective creds for modification. |
258 | * |
259 | * Returns a pointer to the new creds-to-be if successful, NULL otherwise. |
260 | * |
261 | * Call commit_creds() or abort_creds() to clean up. |
262 | */ |
263 | struct cred *prepare_creds(void) |
264 | { |
265 | struct task_struct *task = current; |
266 | const struct cred *old; |
267 | struct cred *new; |
268 | |
269 | validate_process_creds(); |
270 | |
271 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); |
272 | if (!new) |
273 | return NULL; |
274 | |
275 | kdebug("prepare_creds() alloc %p", new); |
276 | |
277 | old = task->cred; |
278 | memcpy(new, old, sizeof(struct cred)); |
279 | |
280 | atomic_set(&new->usage, 1); |
281 | set_cred_subscribers(new, 0); |
282 | get_group_info(new->group_info); |
283 | get_uid(new->user); |
284 | |
285 | #ifdef CONFIG_KEYS |
286 | key_get(new->thread_keyring); |
287 | key_get(new->request_key_auth); |
288 | atomic_inc(&new->tgcred->usage); |
289 | #endif |
290 | |
291 | #ifdef CONFIG_SECURITY |
292 | new->security = NULL; |
293 | #endif |
294 | |
295 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) |
296 | goto error; |
297 | validate_creds(new); |
298 | return new; |
299 | |
300 | error: |
301 | abort_creds(new); |
302 | return NULL; |
303 | } |
304 | EXPORT_SYMBOL(prepare_creds); |
305 | |
306 | /* |
307 | * Prepare credentials for current to perform an execve() |
308 | * - The caller must hold current->cred_guard_mutex |
309 | */ |
310 | struct cred *prepare_exec_creds(void) |
311 | { |
312 | struct thread_group_cred *tgcred = NULL; |
313 | struct cred *new; |
314 | |
315 | #ifdef CONFIG_KEYS |
316 | tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); |
317 | if (!tgcred) |
318 | return NULL; |
319 | #endif |
320 | |
321 | new = prepare_creds(); |
322 | if (!new) { |
323 | kfree(tgcred); |
324 | return new; |
325 | } |
326 | |
327 | #ifdef CONFIG_KEYS |
328 | /* newly exec'd tasks don't get a thread keyring */ |
329 | key_put(new->thread_keyring); |
330 | new->thread_keyring = NULL; |
331 | |
332 | /* create a new per-thread-group creds for all this set of threads to |
333 | * share */ |
334 | memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred)); |
335 | |
336 | atomic_set(&tgcred->usage, 1); |
337 | spin_lock_init(&tgcred->lock); |
338 | |
339 | /* inherit the session keyring; new process keyring */ |
340 | key_get(tgcred->session_keyring); |
341 | tgcred->process_keyring = NULL; |
342 | |
343 | release_tgcred(new); |
344 | new->tgcred = tgcred; |
345 | #endif |
346 | |
347 | return new; |
348 | } |
349 | |
350 | /* |
351 | * prepare new credentials for the usermode helper dispatcher |
352 | */ |
353 | struct cred *prepare_usermodehelper_creds(void) |
354 | { |
355 | #ifdef CONFIG_KEYS |
356 | struct thread_group_cred *tgcred = NULL; |
357 | #endif |
358 | struct cred *new; |
359 | |
360 | #ifdef CONFIG_KEYS |
361 | tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC); |
362 | if (!tgcred) |
363 | return NULL; |
364 | #endif |
365 | |
366 | new = kmem_cache_alloc(cred_jar, GFP_ATOMIC); |
367 | if (!new) |
368 | goto free_tgcred; |
369 | |
370 | kdebug("prepare_usermodehelper_creds() alloc %p", new); |
371 | |
372 | memcpy(new, &init_cred, sizeof(struct cred)); |
373 | |
374 | atomic_set(&new->usage, 1); |
375 | set_cred_subscribers(new, 0); |
376 | get_group_info(new->group_info); |
377 | get_uid(new->user); |
378 | |
379 | #ifdef CONFIG_KEYS |
380 | new->thread_keyring = NULL; |
381 | new->request_key_auth = NULL; |
382 | new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT; |
383 | |
384 | atomic_set(&tgcred->usage, 1); |
385 | spin_lock_init(&tgcred->lock); |
386 | new->tgcred = tgcred; |
387 | #endif |
388 | |
389 | #ifdef CONFIG_SECURITY |
390 | new->security = NULL; |
391 | #endif |
392 | if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0) |
393 | goto error; |
394 | validate_creds(new); |
395 | |
396 | BUG_ON(atomic_read(&new->usage) != 1); |
397 | return new; |
398 | |
399 | error: |
400 | put_cred(new); |
401 | return NULL; |
402 | |
403 | free_tgcred: |
404 | #ifdef CONFIG_KEYS |
405 | kfree(tgcred); |
406 | #endif |
407 | return NULL; |
408 | } |
409 | |
410 | /* |
411 | * Copy credentials for the new process created by fork() |
412 | * |
413 | * We share if we can, but under some circumstances we have to generate a new |
414 | * set. |
415 | * |
416 | * The new process gets the current process's subjective credentials as its |
417 | * objective and subjective credentials |
418 | */ |
419 | int copy_creds(struct task_struct *p, unsigned long clone_flags) |
420 | { |
421 | #ifdef CONFIG_KEYS |
422 | struct thread_group_cred *tgcred; |
423 | #endif |
424 | struct cred *new; |
425 | int ret; |
426 | |
427 | mutex_init(&p->cred_guard_mutex); |
428 | |
429 | if ( |
430 | #ifdef CONFIG_KEYS |
431 | !p->cred->thread_keyring && |
432 | #endif |
433 | clone_flags & CLONE_THREAD |
434 | ) { |
435 | p->real_cred = get_cred(p->cred); |
436 | get_cred(p->cred); |
437 | alter_cred_subscribers(p->cred, 2); |
438 | kdebug("share_creds(%p{%d,%d})", |
439 | p->cred, atomic_read(&p->cred->usage), |
440 | read_cred_subscribers(p->cred)); |
441 | atomic_inc(&p->cred->user->processes); |
442 | return 0; |
443 | } |
444 | |
445 | new = prepare_creds(); |
446 | if (!new) |
447 | return -ENOMEM; |
448 | |
449 | if (clone_flags & CLONE_NEWUSER) { |
450 | ret = create_user_ns(new); |
451 | if (ret < 0) |
452 | goto error_put; |
453 | } |
454 | |
455 | #ifdef CONFIG_KEYS |
456 | /* new threads get their own thread keyrings if their parent already |
457 | * had one */ |
458 | if (new->thread_keyring) { |
459 | key_put(new->thread_keyring); |
460 | new->thread_keyring = NULL; |
461 | if (clone_flags & CLONE_THREAD) |
462 | install_thread_keyring_to_cred(new); |
463 | } |
464 | |
465 | /* we share the process and session keyrings between all the threads in |
466 | * a process - this is slightly icky as we violate COW credentials a |
467 | * bit */ |
468 | if (!(clone_flags & CLONE_THREAD)) { |
469 | tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); |
470 | if (!tgcred) { |
471 | ret = -ENOMEM; |
472 | goto error_put; |
473 | } |
474 | atomic_set(&tgcred->usage, 1); |
475 | spin_lock_init(&tgcred->lock); |
476 | tgcred->process_keyring = NULL; |
477 | tgcred->session_keyring = key_get(new->tgcred->session_keyring); |
478 | |
479 | release_tgcred(new); |
480 | new->tgcred = tgcred; |
481 | } |
482 | #endif |
483 | |
484 | atomic_inc(&new->user->processes); |
485 | p->cred = p->real_cred = get_cred(new); |
486 | alter_cred_subscribers(new, 2); |
487 | validate_creds(new); |
488 | return 0; |
489 | |
490 | error_put: |
491 | put_cred(new); |
492 | return ret; |
493 | } |
494 | |
495 | /** |
496 | * commit_creds - Install new credentials upon the current task |
497 | * @new: The credentials to be assigned |
498 | * |
499 | * Install a new set of credentials to the current task, using RCU to replace |
500 | * the old set. Both the objective and the subjective credentials pointers are |
501 | * updated. This function may not be called if the subjective credentials are |
502 | * in an overridden state. |
503 | * |
504 | * This function eats the caller's reference to the new credentials. |
505 | * |
506 | * Always returns 0 thus allowing this function to be tail-called at the end |
507 | * of, say, sys_setgid(). |
508 | */ |
509 | int commit_creds(struct cred *new) |
510 | { |
511 | struct task_struct *task = current; |
512 | const struct cred *old = task->real_cred; |
513 | |
514 | kdebug("commit_creds(%p{%d,%d})", new, |
515 | atomic_read(&new->usage), |
516 | read_cred_subscribers(new)); |
517 | |
518 | BUG_ON(task->cred != old); |
519 | #ifdef CONFIG_DEBUG_CREDENTIALS |
520 | BUG_ON(read_cred_subscribers(old) < 2); |
521 | validate_creds(old); |
522 | validate_creds(new); |
523 | #endif |
524 | BUG_ON(atomic_read(&new->usage) < 1); |
525 | |
526 | security_commit_creds(new, old); |
527 | |
528 | get_cred(new); /* we will require a ref for the subj creds too */ |
529 | |
530 | /* dumpability changes */ |
531 | if (old->euid != new->euid || |
532 | old->egid != new->egid || |
533 | old->fsuid != new->fsuid || |
534 | old->fsgid != new->fsgid || |
535 | !cap_issubset(new->cap_permitted, old->cap_permitted)) { |
536 | if (task->mm) |
537 | set_dumpable(task->mm, suid_dumpable); |
538 | task->pdeath_signal = 0; |
539 | smp_wmb(); |
540 | } |
541 | |
542 | /* alter the thread keyring */ |
543 | if (new->fsuid != old->fsuid) |
544 | key_fsuid_changed(task); |
545 | if (new->fsgid != old->fsgid) |
546 | key_fsgid_changed(task); |
547 | |
548 | /* do it |
549 | * - What if a process setreuid()'s and this brings the |
550 | * new uid over his NPROC rlimit? We can check this now |
551 | * cheaply with the new uid cache, so if it matters |
552 | * we should be checking for it. -DaveM |
553 | */ |
554 | alter_cred_subscribers(new, 2); |
555 | if (new->user != old->user) |
556 | atomic_inc(&new->user->processes); |
557 | rcu_assign_pointer(task->real_cred, new); |
558 | rcu_assign_pointer(task->cred, new); |
559 | if (new->user != old->user) |
560 | atomic_dec(&old->user->processes); |
561 | alter_cred_subscribers(old, -2); |
562 | |
563 | sched_switch_user(task); |
564 | |
565 | /* send notifications */ |
566 | if (new->uid != old->uid || |
567 | new->euid != old->euid || |
568 | new->suid != old->suid || |
569 | new->fsuid != old->fsuid) |
570 | proc_id_connector(task, PROC_EVENT_UID); |
571 | |
572 | if (new->gid != old->gid || |
573 | new->egid != old->egid || |
574 | new->sgid != old->sgid || |
575 | new->fsgid != old->fsgid) |
576 | proc_id_connector(task, PROC_EVENT_GID); |
577 | |
578 | /* release the old obj and subj refs both */ |
579 | put_cred(old); |
580 | put_cred(old); |
581 | return 0; |
582 | } |
583 | EXPORT_SYMBOL(commit_creds); |
584 | |
585 | /** |
586 | * abort_creds - Discard a set of credentials and unlock the current task |
587 | * @new: The credentials that were going to be applied |
588 | * |
589 | * Discard a set of credentials that were under construction and unlock the |
590 | * current task. |
591 | */ |
592 | void abort_creds(struct cred *new) |
593 | { |
594 | kdebug("abort_creds(%p{%d,%d})", new, |
595 | atomic_read(&new->usage), |
596 | read_cred_subscribers(new)); |
597 | |
598 | #ifdef CONFIG_DEBUG_CREDENTIALS |
599 | BUG_ON(read_cred_subscribers(new) != 0); |
600 | #endif |
601 | BUG_ON(atomic_read(&new->usage) < 1); |
602 | put_cred(new); |
603 | } |
604 | EXPORT_SYMBOL(abort_creds); |
605 | |
606 | /** |
607 | * override_creds - Override the current process's subjective credentials |
608 | * @new: The credentials to be assigned |
609 | * |
610 | * Install a set of temporary override subjective credentials on the current |
611 | * process, returning the old set for later reversion. |
612 | */ |
613 | const struct cred *override_creds(const struct cred *new) |
614 | { |
615 | const struct cred *old = current->cred; |
616 | |
617 | kdebug("override_creds(%p{%d,%d})", new, |
618 | atomic_read(&new->usage), |
619 | read_cred_subscribers(new)); |
620 | |
621 | validate_creds(old); |
622 | validate_creds(new); |
623 | get_cred(new); |
624 | alter_cred_subscribers(new, 1); |
625 | rcu_assign_pointer(current->cred, new); |
626 | alter_cred_subscribers(old, -1); |
627 | |
628 | kdebug("override_creds() = %p{%d,%d}", old, |
629 | atomic_read(&old->usage), |
630 | read_cred_subscribers(old)); |
631 | return old; |
632 | } |
633 | EXPORT_SYMBOL(override_creds); |
634 | |
635 | /** |
636 | * revert_creds - Revert a temporary subjective credentials override |
637 | * @old: The credentials to be restored |
638 | * |
639 | * Revert a temporary set of override subjective credentials to an old set, |
640 | * discarding the override set. |
641 | */ |
642 | void revert_creds(const struct cred *old) |
643 | { |
644 | const struct cred *override = current->cred; |
645 | |
646 | kdebug("revert_creds(%p{%d,%d})", old, |
647 | atomic_read(&old->usage), |
648 | read_cred_subscribers(old)); |
649 | |
650 | validate_creds(old); |
651 | validate_creds(override); |
652 | alter_cred_subscribers(old, 1); |
653 | rcu_assign_pointer(current->cred, old); |
654 | alter_cred_subscribers(override, -1); |
655 | put_cred(override); |
656 | } |
657 | EXPORT_SYMBOL(revert_creds); |
658 | |
659 | /* |
660 | * initialise the credentials stuff |
661 | */ |
662 | void __init cred_init(void) |
663 | { |
664 | /* allocate a slab in which we can store credentials */ |
665 | cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), |
666 | 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); |
667 | } |
668 | |
669 | /** |
670 | * prepare_kernel_cred - Prepare a set of credentials for a kernel service |
671 | * @daemon: A userspace daemon to be used as a reference |
672 | * |
673 | * Prepare a set of credentials for a kernel service. This can then be used to |
674 | * override a task's own credentials so that work can be done on behalf of that |
675 | * task that requires a different subjective context. |
676 | * |
677 | * @daemon is used to provide a base for the security record, but can be NULL. |
678 | * If @daemon is supplied, then the security data will be derived from that; |
679 | * otherwise they'll be set to 0 and no groups, full capabilities and no keys. |
680 | * |
681 | * The caller may change these controls afterwards if desired. |
682 | * |
683 | * Returns the new credentials or NULL if out of memory. |
684 | * |
685 | * Does not take, and does not return holding current->cred_replace_mutex. |
686 | */ |
687 | struct cred *prepare_kernel_cred(struct task_struct *daemon) |
688 | { |
689 | const struct cred *old; |
690 | struct cred *new; |
691 | |
692 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); |
693 | if (!new) |
694 | return NULL; |
695 | |
696 | kdebug("prepare_kernel_cred() alloc %p", new); |
697 | |
698 | if (daemon) |
699 | old = get_task_cred(daemon); |
700 | else |
701 | old = get_cred(&init_cred); |
702 | |
703 | validate_creds(old); |
704 | |
705 | *new = *old; |
706 | get_uid(new->user); |
707 | get_group_info(new->group_info); |
708 | |
709 | #ifdef CONFIG_KEYS |
710 | atomic_inc(&init_tgcred.usage); |
711 | new->tgcred = &init_tgcred; |
712 | new->request_key_auth = NULL; |
713 | new->thread_keyring = NULL; |
714 | new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; |
715 | #endif |
716 | |
717 | #ifdef CONFIG_SECURITY |
718 | new->security = NULL; |
719 | #endif |
720 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) |
721 | goto error; |
722 | |
723 | atomic_set(&new->usage, 1); |
724 | set_cred_subscribers(new, 0); |
725 | put_cred(old); |
726 | validate_creds(new); |
727 | return new; |
728 | |
729 | error: |
730 | put_cred(new); |
731 | put_cred(old); |
732 | return NULL; |
733 | } |
734 | EXPORT_SYMBOL(prepare_kernel_cred); |
735 | |
736 | /** |
737 | * set_security_override - Set the security ID in a set of credentials |
738 | * @new: The credentials to alter |
739 | * @secid: The LSM security ID to set |
740 | * |
741 | * Set the LSM security ID in a set of credentials so that the subjective |
742 | * security is overridden when an alternative set of credentials is used. |
743 | */ |
744 | int set_security_override(struct cred *new, u32 secid) |
745 | { |
746 | return security_kernel_act_as(new, secid); |
747 | } |
748 | EXPORT_SYMBOL(set_security_override); |
749 | |
750 | /** |
751 | * set_security_override_from_ctx - Set the security ID in a set of credentials |
752 | * @new: The credentials to alter |
753 | * @secctx: The LSM security context to generate the security ID from. |
754 | * |
755 | * Set the LSM security ID in a set of credentials so that the subjective |
756 | * security is overridden when an alternative set of credentials is used. The |
757 | * security ID is specified in string form as a security context to be |
758 | * interpreted by the LSM. |
759 | */ |
760 | int set_security_override_from_ctx(struct cred *new, const char *secctx) |
761 | { |
762 | u32 secid; |
763 | int ret; |
764 | |
765 | ret = security_secctx_to_secid(secctx, strlen(secctx), &secid); |
766 | if (ret < 0) |
767 | return ret; |
768 | |
769 | return set_security_override(new, secid); |
770 | } |
771 | EXPORT_SYMBOL(set_security_override_from_ctx); |
772 | |
773 | /** |
774 | * set_create_files_as - Set the LSM file create context in a set of credentials |
775 | * @new: The credentials to alter |
776 | * @inode: The inode to take the context from |
777 | * |
778 | * Change the LSM file creation context in a set of credentials to be the same |
779 | * as the object context of the specified inode, so that the new inodes have |
780 | * the same MAC context as that inode. |
781 | */ |
782 | int set_create_files_as(struct cred *new, struct inode *inode) |
783 | { |
784 | new->fsuid = inode->i_uid; |
785 | new->fsgid = inode->i_gid; |
786 | return security_kernel_create_files_as(new, inode); |
787 | } |
788 | EXPORT_SYMBOL(set_create_files_as); |
789 | |
790 | #ifdef CONFIG_DEBUG_CREDENTIALS |
791 | |
792 | bool creds_are_invalid(const struct cred *cred) |
793 | { |
794 | if (cred->magic != CRED_MAGIC) |
795 | return true; |
796 | #ifdef CONFIG_SECURITY_SELINUX |
797 | if (selinux_is_enabled()) { |
798 | if ((unsigned long) cred->security < PAGE_SIZE) |
799 | return true; |
800 | if ((*(u32 *)cred->security & 0xffffff00) == |
801 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)) |
802 | return true; |
803 | } |
804 | #endif |
805 | return false; |
806 | } |
807 | EXPORT_SYMBOL(creds_are_invalid); |
808 | |
809 | /* |
810 | * dump invalid credentials |
811 | */ |
812 | static void dump_invalid_creds(const struct cred *cred, const char *label, |
813 | const struct task_struct *tsk) |
814 | { |
815 | printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n", |
816 | label, cred, |
817 | cred == &init_cred ? "[init]" : "", |
818 | cred == tsk->real_cred ? "[real]" : "", |
819 | cred == tsk->cred ? "[eff]" : ""); |
820 | printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n", |
821 | cred->magic, cred->put_addr); |
822 | printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n", |
823 | atomic_read(&cred->usage), |
824 | read_cred_subscribers(cred)); |
825 | printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n", |
826 | cred->uid, cred->euid, cred->suid, cred->fsuid); |
827 | printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n", |
828 | cred->gid, cred->egid, cred->sgid, cred->fsgid); |
829 | #ifdef CONFIG_SECURITY |
830 | printk(KERN_ERR "CRED: ->security is %p\n", cred->security); |
831 | if ((unsigned long) cred->security >= PAGE_SIZE && |
832 | (((unsigned long) cred->security & 0xffffff00) != |
833 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))) |
834 | printk(KERN_ERR "CRED: ->security {%x, %x}\n", |
835 | ((u32*)cred->security)[0], |
836 | ((u32*)cred->security)[1]); |
837 | #endif |
838 | } |
839 | |
840 | /* |
841 | * report use of invalid credentials |
842 | */ |
843 | void __invalid_creds(const struct cred *cred, const char *file, unsigned line) |
844 | { |
845 | printk(KERN_ERR "CRED: Invalid credentials\n"); |
846 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); |
847 | dump_invalid_creds(cred, "Specified", current); |
848 | BUG(); |
849 | } |
850 | EXPORT_SYMBOL(__invalid_creds); |
851 | |
852 | /* |
853 | * check the credentials on a process |
854 | */ |
855 | void __validate_process_creds(struct task_struct *tsk, |
856 | const char *file, unsigned line) |
857 | { |
858 | if (tsk->cred == tsk->real_cred) { |
859 | if (unlikely(read_cred_subscribers(tsk->cred) < 2 || |
860 | creds_are_invalid(tsk->cred))) |
861 | goto invalid_creds; |
862 | } else { |
863 | if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 || |
864 | read_cred_subscribers(tsk->cred) < 1 || |
865 | creds_are_invalid(tsk->real_cred) || |
866 | creds_are_invalid(tsk->cred))) |
867 | goto invalid_creds; |
868 | } |
869 | return; |
870 | |
871 | invalid_creds: |
872 | printk(KERN_ERR "CRED: Invalid process credentials\n"); |
873 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); |
874 | |
875 | dump_invalid_creds(tsk->real_cred, "Real", tsk); |
876 | if (tsk->cred != tsk->real_cred) |
877 | dump_invalid_creds(tsk->cred, "Effective", tsk); |
878 | else |
879 | printk(KERN_ERR "CRED: Effective creds == Real creds\n"); |
880 | BUG(); |
881 | } |
882 | EXPORT_SYMBOL(__validate_process_creds); |
883 | |
884 | /* |
885 | * check creds for do_exit() |
886 | */ |
887 | void validate_creds_for_do_exit(struct task_struct *tsk) |
888 | { |
889 | kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})", |
890 | tsk->real_cred, tsk->cred, |
891 | atomic_read(&tsk->cred->usage), |
892 | read_cred_subscribers(tsk->cred)); |
893 | |
894 | __validate_process_creds(tsk, __FILE__, __LINE__); |
895 | } |
896 | |
897 | #endif /* CONFIG_DEBUG_CREDENTIALS */ |
898 |
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