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Randy Dunlapd410fa42011-05-19 15:59:38 -07001/* Task credentials management - see Documentation/security/credentials.txt
David Howellsf1752ee2008-11-14 10:39:17 +11002 *
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 */
Paul Gortmaker9984de12011-05-23 14:51:41 -040011#include <linux/export.h>
David Howellsf1752ee2008-11-14 10:39:17 +110012#include <linux/cred.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090013#include <linux/slab.h>
David Howellsf1752ee2008-11-14 10:39:17 +110014#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>
Al Viro40401532012-02-13 03:58:52 +000019#include <linux/binfmts.h>
David Howellsd84f4f92008-11-14 10:39:23 +110020#include <linux/cn_proc.h>
David Howellsd84f4f92008-11-14 10:39:23 +110021
David Howellse0e81732009-09-02 09:13:40 +010022#if 0
23#define kdebug(FMT, ...) \
24 printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
25#else
David Howellse0e81732009-09-02 09:13:40 +010026#define kdebug(FMT, ...) \
27 no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
28#endif
29
David Howellsd84f4f92008-11-14 10:39:23 +110030static struct kmem_cache *cred_jar;
David Howellsf1752ee2008-11-14 10:39:17 +110031
32/*
David Howellsbb952bb2008-11-14 10:39:20 +110033 * The common credentials for the initial task's thread group
34 */
35#ifdef CONFIG_KEYS
36static struct thread_group_cred init_tgcred = {
37 .usage = ATOMIC_INIT(2),
38 .tgid = 0,
Thomas Gleixner10389a12011-01-23 15:25:56 +010039 .lock = __SPIN_LOCK_UNLOCKED(init_cred.tgcred.lock),
David Howellsbb952bb2008-11-14 10:39:20 +110040};
41#endif
42
43/*
David Howellsf1752ee2008-11-14 10:39:17 +110044 * The initial credentials for the initial task
45 */
46struct cred init_cred = {
David Howells3b11a1d2008-11-14 10:39:26 +110047 .usage = ATOMIC_INIT(4),
David Howellse0e81732009-09-02 09:13:40 +010048#ifdef CONFIG_DEBUG_CREDENTIALS
49 .subscribers = ATOMIC_INIT(2),
50 .magic = CRED_MAGIC,
51#endif
Eric W. Biederman078de5f2012-02-08 07:00:08 -080052 .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,
David Howellsf1752ee2008-11-14 10:39:17 +110060 .securebits = SECUREBITS_DEFAULT,
Eric Parisa3232d22011-04-01 17:08:45 -040061 .cap_inheritable = CAP_EMPTY_SET,
David Howellsf1752ee2008-11-14 10:39:17 +110062 .cap_permitted = CAP_FULL_SET,
Eric Parisa3232d22011-04-01 17:08:45 -040063 .cap_effective = CAP_FULL_SET,
64 .cap_bset = CAP_FULL_SET,
David Howellsf1752ee2008-11-14 10:39:17 +110065 .user = INIT_USER,
Serge E. Hallyn47a150e2011-05-13 04:27:54 +010066 .user_ns = &init_user_ns,
David Howellsf1752ee2008-11-14 10:39:17 +110067 .group_info = &init_groups,
David Howellsbb952bb2008-11-14 10:39:20 +110068#ifdef CONFIG_KEYS
69 .tgcred = &init_tgcred,
70#endif
David Howellsf1752ee2008-11-14 10:39:17 +110071};
72
David Howellse0e81732009-09-02 09:13:40 +010073static 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
80static 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
89static 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
David Howellsf1752ee2008-11-14 10:39:17 +110098/*
David Howellsbb952bb2008-11-14 10:39:20 +110099 * Dispose of the shared task group credentials
100 */
101#ifdef CONFIG_KEYS
102static 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 */
David Howellsa6f76f22008-11-14 10:39:24 +1100118static void release_tgcred(struct cred *cred)
David Howellsbb952bb2008-11-14 10:39:20 +1100119{
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/*
David Howellsf1752ee2008-11-14 10:39:17 +1100129 * The RCU callback to actually dispose of a set of credentials
130 */
131static void put_cred_rcu(struct rcu_head *rcu)
132{
133 struct cred *cred = container_of(rcu, struct cred, rcu);
134
David Howellse0e81732009-09-02 09:13:40 +0100135 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
David Howellsd84f4f92008-11-14 10:39:23 +1100147 if (atomic_read(&cred->usage) != 0)
148 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
149 cred, atomic_read(&cred->usage));
David Howellse0e81732009-09-02 09:13:40 +0100150#endif
David Howellsf1752ee2008-11-14 10:39:17 +1100151
David Howellsd84f4f92008-11-14 10:39:23 +1100152 security_cred_free(cred);
David Howellsf1752ee2008-11-14 10:39:17 +1100153 key_put(cred->thread_keyring);
154 key_put(cred->request_key_auth);
David Howellsbb952bb2008-11-14 10:39:20 +1100155 release_tgcred(cred);
David Howells4a5d6ba2009-09-14 12:45:39 +0100156 if (cred->group_info)
157 put_group_info(cred->group_info);
David Howellsf1752ee2008-11-14 10:39:17 +1100158 free_uid(cred->user);
Eric W. Biederman0093ccb2011-11-16 21:52:53 -0800159 put_user_ns(cred->user_ns);
David Howellsd84f4f92008-11-14 10:39:23 +1100160 kmem_cache_free(cred_jar, cred);
David Howellsf1752ee2008-11-14 10:39:17 +1100161}
162
163/**
164 * __put_cred - Destroy a set of credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100165 * @cred: The record to release
David Howellsf1752ee2008-11-14 10:39:17 +1100166 *
167 * Destroy a set of credentials on which no references remain.
168 */
169void __put_cred(struct cred *cred)
170{
David Howellse0e81732009-09-02 09:13:40 +0100171 kdebug("__put_cred(%p{%d,%d})", cred,
172 atomic_read(&cred->usage),
173 read_cred_subscribers(cred));
174
David Howellsd84f4f92008-11-14 10:39:23 +1100175 BUG_ON(atomic_read(&cred->usage) != 0);
David Howellse0e81732009-09-02 09:13:40 +0100176#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);
David Howellsd84f4f92008-11-14 10:39:23 +1100183
David Howellsf1752ee2008-11-14 10:39:17 +1100184 call_rcu(&cred->rcu, put_cred_rcu);
185}
186EXPORT_SYMBOL(__put_cred);
187
David Howellse0e81732009-09-02 09:13:40 +0100188/*
189 * Clean up a task's credentials when it exits
190 */
191void 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);
David Howellsee18d642009-09-02 09:14:21 +0100210}
211
David Howellsde09a972010-07-29 12:45:49 +0100212/**
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 */
222const 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
David Howellsee18d642009-09-02 09:14:21 +0100237/*
238 * Allocate blank credentials, such that the credentials can be filled in at a
239 * later date without risk of ENOMEM.
240 */
241struct 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) {
Julia Lawallb8a1d372010-02-03 09:31:36 +1100252 kmem_cache_free(cred_jar, new);
David Howellsee18d642009-09-02 09:14:21 +0100253 return NULL;
254 }
255 atomic_set(&new->tgcred->usage, 1);
256#endif
257
258 atomic_set(&new->usage, 1);
Tetsuo Handa2edeaa32011-02-07 13:36:10 +0000259#ifdef CONFIG_DEBUG_CREDENTIALS
260 new->magic = CRED_MAGIC;
261#endif
David Howellsee18d642009-09-02 09:14:21 +0100262
263 if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
264 goto error;
265
David Howellsee18d642009-09-02 09:14:21 +0100266 return new;
267
268error:
269 abort_creds(new);
270 return NULL;
David Howellse0e81732009-09-02 09:13:40 +0100271}
272
David Howellsd84f4f92008-11-14 10:39:23 +1100273/**
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 *
David Howells3b11a1d2008-11-14 10:39:26 +1100281 * Preparation involves making a copy of the objective creds for modification.
282 *
David Howellsd84f4f92008-11-14 10:39:23 +1100283 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
284 *
285 * Call commit_creds() or abort_creds() to clean up.
David Howellsf1752ee2008-11-14 10:39:17 +1100286 */
David Howellsd84f4f92008-11-14 10:39:23 +1100287struct cred *prepare_creds(void)
David Howellsf1752ee2008-11-14 10:39:17 +1100288{
David Howellsd84f4f92008-11-14 10:39:23 +1100289 struct task_struct *task = current;
290 const struct cred *old;
291 struct cred *new;
David Howellsf1752ee2008-11-14 10:39:17 +1100292
David Howellse0e81732009-09-02 09:13:40 +0100293 validate_process_creds();
David Howellsd84f4f92008-11-14 10:39:23 +1100294
295 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
296 if (!new)
297 return NULL;
298
David Howellse0e81732009-09-02 09:13:40 +0100299 kdebug("prepare_creds() alloc %p", new);
300
David Howellsd84f4f92008-11-14 10:39:23 +1100301 old = task->cred;
302 memcpy(new, old, sizeof(struct cred));
303
304 atomic_set(&new->usage, 1);
David Howellse0e81732009-09-02 09:13:40 +0100305 set_cred_subscribers(new, 0);
David Howellsd84f4f92008-11-14 10:39:23 +1100306 get_group_info(new->group_info);
307 get_uid(new->user);
Eric W. Biederman0093ccb2011-11-16 21:52:53 -0800308 get_user_ns(new->user_ns);
David Howellsf1752ee2008-11-14 10:39:17 +1100309
David Howellsbb952bb2008-11-14 10:39:20 +1100310#ifdef CONFIG_KEYS
David Howellsd84f4f92008-11-14 10:39:23 +1100311 key_get(new->thread_keyring);
312 key_get(new->request_key_auth);
313 atomic_inc(&new->tgcred->usage);
David Howellsbb952bb2008-11-14 10:39:20 +1100314#endif
315
David Howellsf1752ee2008-11-14 10:39:17 +1100316#ifdef CONFIG_SECURITY
David Howellsd84f4f92008-11-14 10:39:23 +1100317 new->security = NULL;
David Howellsf1752ee2008-11-14 10:39:17 +1100318#endif
319
David Howellsd84f4f92008-11-14 10:39:23 +1100320 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
321 goto error;
David Howellse0e81732009-09-02 09:13:40 +0100322 validate_creds(new);
David Howellsd84f4f92008-11-14 10:39:23 +1100323 return new;
324
325error:
326 abort_creds(new);
327 return NULL;
328}
329EXPORT_SYMBOL(prepare_creds);
330
331/*
David Howellsa6f76f22008-11-14 10:39:24 +1100332 * Prepare credentials for current to perform an execve()
KOSAKI Motohiro9b1bf122010-10-27 15:34:08 -0700333 * - The caller must hold ->cred_guard_mutex
David Howellsa6f76f22008-11-14 10:39:24 +1100334 */
335struct 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/*
David Howellsd84f4f92008-11-14 10:39:23 +1100376 * 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.
David Howells3b11a1d2008-11-14 10:39:26 +1100380 *
381 * The new process gets the current process's subjective credentials as its
382 * objective and subjective credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100383 */
384int 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;
Serge Hallyn18b6e042008-10-15 16:38:45 -0500390 int ret;
David Howellsd84f4f92008-11-14 10:39:23 +1100391
David Howellsd84f4f92008-11-14 10:39:23 +1100392 if (
393#ifdef CONFIG_KEYS
394 !p->cred->thread_keyring &&
395#endif
396 clone_flags & CLONE_THREAD
397 ) {
David Howells3b11a1d2008-11-14 10:39:26 +1100398 p->real_cred = get_cred(p->cred);
David Howellsd84f4f92008-11-14 10:39:23 +1100399 get_cred(p->cred);
David Howellse0e81732009-09-02 09:13:40 +0100400 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));
David Howellsd84f4f92008-11-14 10:39:23 +1100404 atomic_inc(&p->cred->user->processes);
405 return 0;
David Howellsf1752ee2008-11-14 10:39:17 +1100406 }
407
David Howellsd84f4f92008-11-14 10:39:23 +1100408 new = prepare_creds();
409 if (!new)
410 return -ENOMEM;
David Howellsf1752ee2008-11-14 10:39:17 +1100411
Serge Hallyn18b6e042008-10-15 16:38:45 -0500412 if (clone_flags & CLONE_NEWUSER) {
413 ret = create_user_ns(new);
414 if (ret < 0)
415 goto error_put;
416 }
417
David Howellsd84f4f92008-11-14 10:39:23 +1100418#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 }
David Howellsf1752ee2008-11-14 10:39:17 +1100427
David Howellsd84f4f92008-11-14 10:39:23 +1100428 /* 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) {
Serge Hallyn18b6e042008-10-15 16:38:45 -0500434 ret = -ENOMEM;
435 goto error_put;
David Howellsd84f4f92008-11-14 10:39:23 +1100436 }
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);
David Howells3b11a1d2008-11-14 10:39:26 +1100448 p->cred = p->real_cred = get_cred(new);
David Howellse0e81732009-09-02 09:13:40 +0100449 alter_cred_subscribers(new, 2);
450 validate_creds(new);
David Howellsf1752ee2008-11-14 10:39:17 +1100451 return 0;
Serge Hallyn18b6e042008-10-15 16:38:45 -0500452
453error_put:
454 put_cred(new);
455 return ret;
David Howellsf1752ee2008-11-14 10:39:17 +1100456}
David Howellsd84f4f92008-11-14 10:39:23 +1100457
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
David Howells3b11a1d2008-11-14 10:39:26 +1100463 * 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.
David Howellsd84f4f92008-11-14 10:39:23 +1100466 *
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 */
472int commit_creds(struct cred *new)
473{
474 struct task_struct *task = current;
David Howellse0e81732009-09-02 09:13:40 +0100475 const struct cred *old = task->real_cred;
David Howellsd84f4f92008-11-14 10:39:23 +1100476
David Howellse0e81732009-09-02 09:13:40 +0100477 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
David Howellsd84f4f92008-11-14 10:39:23 +1100487 BUG_ON(atomic_read(&new->usage) < 1);
David Howellsd84f4f92008-11-14 10:39:23 +1100488
David Howells3b11a1d2008-11-14 10:39:26 +1100489 get_cred(new); /* we will require a ref for the subj creds too */
490
David Howellsd84f4f92008-11-14 10:39:23 +1100491 /* dumpability changes */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800492 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) ||
David Howellsd84f4f92008-11-14 10:39:23 +1100496 !cap_issubset(new->cap_permitted, old->cap_permitted)) {
David Howellsb9456372009-01-08 11:18:31 +0000497 if (task->mm)
498 set_dumpable(task->mm, suid_dumpable);
David Howellsd84f4f92008-11-14 10:39:23 +1100499 task->pdeath_signal = 0;
500 smp_wmb();
501 }
502
503 /* alter the thread keyring */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800504 if (!uid_eq(new->fsuid, old->fsuid))
David Howellsd84f4f92008-11-14 10:39:23 +1100505 key_fsuid_changed(task);
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800506 if (!gid_eq(new->fsgid, old->fsgid))
David Howellsd84f4f92008-11-14 10:39:23 +1100507 key_fsgid_changed(task);
508
509 /* do it
Vasiliy Kulikov72fa5992011-08-08 19:02:04 +0400510 * RLIMIT_NPROC limits on user->processes have already been checked
511 * in set_user().
David Howellsd84f4f92008-11-14 10:39:23 +1100512 */
David Howellse0e81732009-09-02 09:13:40 +0100513 alter_cred_subscribers(new, 2);
David Howellsd84f4f92008-11-14 10:39:23 +1100514 if (new->user != old->user)
515 atomic_inc(&new->user->processes);
David Howells3b11a1d2008-11-14 10:39:26 +1100516 rcu_assign_pointer(task->real_cred, new);
David Howellsd84f4f92008-11-14 10:39:23 +1100517 rcu_assign_pointer(task->cred, new);
518 if (new->user != old->user)
519 atomic_dec(&old->user->processes);
David Howellse0e81732009-09-02 09:13:40 +0100520 alter_cred_subscribers(old, -2);
David Howellsd84f4f92008-11-14 10:39:23 +1100521
David Howellsd84f4f92008-11-14 10:39:23 +1100522 /* send notifications */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800523 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))
David Howellsd84f4f92008-11-14 10:39:23 +1100527 proc_id_connector(task, PROC_EVENT_UID);
528
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800529 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))
David Howellsd84f4f92008-11-14 10:39:23 +1100533 proc_id_connector(task, PROC_EVENT_GID);
534
David Howells3b11a1d2008-11-14 10:39:26 +1100535 /* release the old obj and subj refs both */
536 put_cred(old);
David Howellsd84f4f92008-11-14 10:39:23 +1100537 put_cred(old);
538 return 0;
539}
540EXPORT_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 */
549void abort_creds(struct cred *new)
550{
David Howellse0e81732009-09-02 09:13:40 +0100551 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
David Howellsd84f4f92008-11-14 10:39:23 +1100558 BUG_ON(atomic_read(&new->usage) < 1);
559 put_cred(new);
560}
561EXPORT_SYMBOL(abort_creds);
562
563/**
David Howells3b11a1d2008-11-14 10:39:26 +1100564 * override_creds - Override the current process's subjective credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100565 * @new: The credentials to be assigned
566 *
David Howells3b11a1d2008-11-14 10:39:26 +1100567 * Install a set of temporary override subjective credentials on the current
568 * process, returning the old set for later reversion.
David Howellsd84f4f92008-11-14 10:39:23 +1100569 */
570const struct cred *override_creds(const struct cred *new)
571{
572 const struct cred *old = current->cred;
573
David Howellse0e81732009-09-02 09:13:40 +0100574 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));
David Howellsd84f4f92008-11-14 10:39:23 +1100588 return old;
589}
590EXPORT_SYMBOL(override_creds);
591
592/**
David Howells3b11a1d2008-11-14 10:39:26 +1100593 * revert_creds - Revert a temporary subjective credentials override
David Howellsd84f4f92008-11-14 10:39:23 +1100594 * @old: The credentials to be restored
595 *
David Howells3b11a1d2008-11-14 10:39:26 +1100596 * Revert a temporary set of override subjective credentials to an old set,
597 * discarding the override set.
David Howellsd84f4f92008-11-14 10:39:23 +1100598 */
599void revert_creds(const struct cred *old)
600{
601 const struct cred *override = current->cred;
602
David Howellse0e81732009-09-02 09:13:40 +0100603 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);
David Howellsd84f4f92008-11-14 10:39:23 +1100610 rcu_assign_pointer(current->cred, old);
David Howellse0e81732009-09-02 09:13:40 +0100611 alter_cred_subscribers(override, -1);
David Howellsd84f4f92008-11-14 10:39:23 +1100612 put_cred(override);
613}
614EXPORT_SYMBOL(revert_creds);
615
616/*
617 * initialise the credentials stuff
618 */
619void __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}
David Howells3a3b7ce2008-11-14 10:39:28 +1100625
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 */
644struct cred *prepare_kernel_cred(struct task_struct *daemon)
645{
David Howells012146d2011-08-22 14:09:00 +0100646#ifdef CONFIG_KEYS
647 struct thread_group_cred *tgcred;
648#endif
David Howells3a3b7ce2008-11-14 10:39:28 +1100649 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
Axel Lin8ad346c2011-08-23 15:23:51 +0800656#ifdef CONFIG_KEYS
David Howells012146d2011-08-22 14:09:00 +0100657 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
658 if (!tgcred) {
659 kmem_cache_free(cred_jar, new);
660 return NULL;
661 }
Axel Lin8ad346c2011-08-23 15:23:51 +0800662#endif
David Howells012146d2011-08-22 14:09:00 +0100663
David Howellse0e81732009-09-02 09:13:40 +0100664 kdebug("prepare_kernel_cred() alloc %p", new);
665
David Howells3a3b7ce2008-11-14 10:39:28 +1100666 if (daemon)
667 old = get_task_cred(daemon);
668 else
669 old = get_cred(&init_cred);
670
David Howellse0e81732009-09-02 09:13:40 +0100671 validate_creds(old);
672
David Howells43529c92009-01-09 16:13:46 +0000673 *new = *old;
Tetsuo Handafb2b2a12011-02-07 13:36:16 +0000674 atomic_set(&new->usage, 1);
675 set_cred_subscribers(new, 0);
David Howells3a3b7ce2008-11-14 10:39:28 +1100676 get_uid(new->user);
Eric W. Biederman0093ccb2011-11-16 21:52:53 -0800677 get_user_ns(new->user_ns);
David Howells3a3b7ce2008-11-14 10:39:28 +1100678 get_group_info(new->group_info);
679
680#ifdef CONFIG_KEYS
David Howells012146d2011-08-22 14:09:00 +0100681 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;
David Howells3a3b7ce2008-11-14 10:39:28 +1100686 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
David Howells3a3b7ce2008-11-14 10:39:28 +1100697 put_cred(old);
David Howellse0e81732009-09-02 09:13:40 +0100698 validate_creds(new);
David Howells3a3b7ce2008-11-14 10:39:28 +1100699 return new;
700
701error:
702 put_cred(new);
David Howells0de33682009-01-09 16:13:41 +0000703 put_cred(old);
David Howells3a3b7ce2008-11-14 10:39:28 +1100704 return NULL;
705}
706EXPORT_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 */
716int set_security_override(struct cred *new, u32 secid)
717{
718 return security_kernel_act_as(new, secid);
719}
720EXPORT_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 */
732int 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}
743EXPORT_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 */
754int 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}
760EXPORT_SYMBOL(set_create_files_as);
David Howellse0e81732009-09-02 09:13:40 +0100761
762#ifdef CONFIG_DEBUG_CREDENTIALS
763
Andrew Morton74908a02009-09-17 17:47:12 -0700764bool creds_are_invalid(const struct cred *cred)
765{
766 if (cred->magic != CRED_MAGIC)
767 return true;
Andrew Morton74908a02009-09-17 17:47:12 -0700768#ifdef CONFIG_SECURITY_SELINUX
Tetsuo Handa2edeaa32011-02-07 13:36:10 +0000769 /*
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) {
Andrew Morton74908a02009-09-17 17:47:12 -0700774 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}
Randy Dunlap764db032009-09-18 11:06:47 -0700783EXPORT_SYMBOL(creds_are_invalid);
Andrew Morton74908a02009-09-17 17:47:12 -0700784
David Howellse0e81732009-09-02 09:13:40 +0100785/*
786 * dump invalid credentials
787 */
788static 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 */
819void __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}
826EXPORT_SYMBOL(__invalid_creds);
827
828/*
829 * check the credentials on a process
830 */
831void __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
847invalid_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}
858EXPORT_SYMBOL(__validate_process_creds);
859
860/*
861 * check creds for do_exit()
862 */
863void 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 */