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Randy Dunlapd410fa4e2011-05-19 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/*
33 * The initial credentials for the initial task
34 */
35struct cred init_cred = {
David Howells3b11a1d2008-11-14 10:39:26 +110036 .usage = ATOMIC_INIT(4),
David Howellse0e81732009-09-02 09:13:40 +010037#ifdef CONFIG_DEBUG_CREDENTIALS
38 .subscribers = ATOMIC_INIT(2),
39 .magic = CRED_MAGIC,
40#endif
Eric W. Biederman078de5f2012-02-08 07:00:08 -080041 .uid = GLOBAL_ROOT_UID,
42 .gid = GLOBAL_ROOT_GID,
43 .suid = GLOBAL_ROOT_UID,
44 .sgid = GLOBAL_ROOT_GID,
45 .euid = GLOBAL_ROOT_UID,
46 .egid = GLOBAL_ROOT_GID,
47 .fsuid = GLOBAL_ROOT_UID,
48 .fsgid = GLOBAL_ROOT_GID,
David Howellsf1752ee2008-11-14 10:39:17 +110049 .securebits = SECUREBITS_DEFAULT,
Eric Parisa3232d22011-04-01 17:08:45 -040050 .cap_inheritable = CAP_EMPTY_SET,
David Howellsf1752ee2008-11-14 10:39:17 +110051 .cap_permitted = CAP_FULL_SET,
Eric Parisa3232d22011-04-01 17:08:45 -040052 .cap_effective = CAP_FULL_SET,
53 .cap_bset = CAP_FULL_SET,
David Howellsf1752ee2008-11-14 10:39:17 +110054 .user = INIT_USER,
Serge E. Hallyn47a150e2011-05-13 04:27:54 +010055 .user_ns = &init_user_ns,
David Howellsf1752ee2008-11-14 10:39:17 +110056 .group_info = &init_groups,
57};
58
David Howellse0e81732009-09-02 09:13:40 +010059static inline void set_cred_subscribers(struct cred *cred, int n)
60{
61#ifdef CONFIG_DEBUG_CREDENTIALS
62 atomic_set(&cred->subscribers, n);
63#endif
64}
65
66static inline int read_cred_subscribers(const struct cred *cred)
67{
68#ifdef CONFIG_DEBUG_CREDENTIALS
69 return atomic_read(&cred->subscribers);
70#else
71 return 0;
72#endif
73}
74
75static inline void alter_cred_subscribers(const struct cred *_cred, int n)
76{
77#ifdef CONFIG_DEBUG_CREDENTIALS
78 struct cred *cred = (struct cred *) _cred;
79
80 atomic_add(n, &cred->subscribers);
81#endif
82}
83
David Howellsf1752ee2008-11-14 10:39:17 +110084/*
85 * The RCU callback to actually dispose of a set of credentials
86 */
87static void put_cred_rcu(struct rcu_head *rcu)
88{
89 struct cred *cred = container_of(rcu, struct cred, rcu);
90
David Howellse0e81732009-09-02 09:13:40 +010091 kdebug("put_cred_rcu(%p)", cred);
92
93#ifdef CONFIG_DEBUG_CREDENTIALS
94 if (cred->magic != CRED_MAGIC_DEAD ||
95 atomic_read(&cred->usage) != 0 ||
96 read_cred_subscribers(cred) != 0)
97 panic("CRED: put_cred_rcu() sees %p with"
98 " mag %x, put %p, usage %d, subscr %d\n",
99 cred, cred->magic, cred->put_addr,
100 atomic_read(&cred->usage),
101 read_cred_subscribers(cred));
102#else
David Howellsd84f4f92008-11-14 10:39:23 +1100103 if (atomic_read(&cred->usage) != 0)
104 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
105 cred, atomic_read(&cred->usage));
David Howellse0e81732009-09-02 09:13:40 +0100106#endif
David Howellsf1752ee2008-11-14 10:39:17 +1100107
David Howellsd84f4f92008-11-14 10:39:23 +1100108 security_cred_free(cred);
David Howells3a505972012-10-02 19:24:29 +0100109 key_put(cred->session_keyring);
110 key_put(cred->process_keyring);
David Howellsf1752ee2008-11-14 10:39:17 +1100111 key_put(cred->thread_keyring);
112 key_put(cred->request_key_auth);
David Howells4a5d6ba2009-09-14 12:45:39 +0100113 if (cred->group_info)
114 put_group_info(cred->group_info);
David Howellsf1752ee2008-11-14 10:39:17 +1100115 free_uid(cred->user);
Eric W. Biederman0093ccb2011-11-16 21:52:53 -0800116 put_user_ns(cred->user_ns);
David Howellsd84f4f92008-11-14 10:39:23 +1100117 kmem_cache_free(cred_jar, cred);
David Howellsf1752ee2008-11-14 10:39:17 +1100118}
119
120/**
121 * __put_cred - Destroy a set of credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100122 * @cred: The record to release
David Howellsf1752ee2008-11-14 10:39:17 +1100123 *
124 * Destroy a set of credentials on which no references remain.
125 */
126void __put_cred(struct cred *cred)
127{
David Howellse0e81732009-09-02 09:13:40 +0100128 kdebug("__put_cred(%p{%d,%d})", cred,
129 atomic_read(&cred->usage),
130 read_cred_subscribers(cred));
131
David Howellsd84f4f92008-11-14 10:39:23 +1100132 BUG_ON(atomic_read(&cred->usage) != 0);
David Howellse0e81732009-09-02 09:13:40 +0100133#ifdef CONFIG_DEBUG_CREDENTIALS
134 BUG_ON(read_cred_subscribers(cred) != 0);
135 cred->magic = CRED_MAGIC_DEAD;
136 cred->put_addr = __builtin_return_address(0);
137#endif
138 BUG_ON(cred == current->cred);
139 BUG_ON(cred == current->real_cred);
David Howellsd84f4f92008-11-14 10:39:23 +1100140
David Howellsf1752ee2008-11-14 10:39:17 +1100141 call_rcu(&cred->rcu, put_cred_rcu);
142}
143EXPORT_SYMBOL(__put_cred);
144
David Howellse0e81732009-09-02 09:13:40 +0100145/*
146 * Clean up a task's credentials when it exits
147 */
148void exit_creds(struct task_struct *tsk)
149{
150 struct cred *cred;
151
152 kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
153 atomic_read(&tsk->cred->usage),
154 read_cred_subscribers(tsk->cred));
155
156 cred = (struct cred *) tsk->real_cred;
157 tsk->real_cred = NULL;
158 validate_creds(cred);
159 alter_cred_subscribers(cred, -1);
160 put_cred(cred);
161
162 cred = (struct cred *) tsk->cred;
163 tsk->cred = NULL;
164 validate_creds(cred);
165 alter_cred_subscribers(cred, -1);
166 put_cred(cred);
David Howellsee18d642009-09-02 09:14:21 +0100167}
168
David Howellsde09a972010-07-29 12:45:49 +0100169/**
170 * get_task_cred - Get another task's objective credentials
171 * @task: The task to query
172 *
173 * Get the objective credentials of a task, pinning them so that they can't go
174 * away. Accessing a task's credentials directly is not permitted.
175 *
176 * The caller must also make sure task doesn't get deleted, either by holding a
177 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
178 */
179const struct cred *get_task_cred(struct task_struct *task)
180{
181 const struct cred *cred;
182
183 rcu_read_lock();
184
185 do {
186 cred = __task_cred((task));
187 BUG_ON(!cred);
188 } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
189
190 rcu_read_unlock();
191 return cred;
192}
193
David Howellsee18d642009-09-02 09:14:21 +0100194/*
195 * Allocate blank credentials, such that the credentials can be filled in at a
196 * later date without risk of ENOMEM.
197 */
198struct cred *cred_alloc_blank(void)
199{
200 struct cred *new;
201
202 new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
203 if (!new)
204 return NULL;
205
David Howellsee18d642009-09-02 09:14:21 +0100206 atomic_set(&new->usage, 1);
Tetsuo Handa2edeaa32011-02-07 13:36:10 +0000207#ifdef CONFIG_DEBUG_CREDENTIALS
208 new->magic = CRED_MAGIC;
209#endif
David Howellsee18d642009-09-02 09:14:21 +0100210
211 if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
212 goto error;
213
David Howellsee18d642009-09-02 09:14:21 +0100214 return new;
215
216error:
217 abort_creds(new);
218 return NULL;
David Howellse0e81732009-09-02 09:13:40 +0100219}
220
David Howellsd84f4f92008-11-14 10:39:23 +1100221/**
222 * prepare_creds - Prepare a new set of credentials for modification
223 *
224 * Prepare a new set of task credentials for modification. A task's creds
225 * shouldn't generally be modified directly, therefore this function is used to
226 * prepare a new copy, which the caller then modifies and then commits by
227 * calling commit_creds().
228 *
David Howells3b11a1d2008-11-14 10:39:26 +1100229 * Preparation involves making a copy of the objective creds for modification.
230 *
David Howellsd84f4f92008-11-14 10:39:23 +1100231 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
232 *
233 * Call commit_creds() or abort_creds() to clean up.
David Howellsf1752ee2008-11-14 10:39:17 +1100234 */
David Howellsd84f4f92008-11-14 10:39:23 +1100235struct cred *prepare_creds(void)
David Howellsf1752ee2008-11-14 10:39:17 +1100236{
David Howellsd84f4f92008-11-14 10:39:23 +1100237 struct task_struct *task = current;
238 const struct cred *old;
239 struct cred *new;
David Howellsf1752ee2008-11-14 10:39:17 +1100240
David Howellse0e81732009-09-02 09:13:40 +0100241 validate_process_creds();
David Howellsd84f4f92008-11-14 10:39:23 +1100242
243 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
244 if (!new)
245 return NULL;
246
David Howellse0e81732009-09-02 09:13:40 +0100247 kdebug("prepare_creds() alloc %p", new);
248
David Howellsd84f4f92008-11-14 10:39:23 +1100249 old = task->cred;
250 memcpy(new, old, sizeof(struct cred));
251
252 atomic_set(&new->usage, 1);
David Howellse0e81732009-09-02 09:13:40 +0100253 set_cred_subscribers(new, 0);
David Howellsd84f4f92008-11-14 10:39:23 +1100254 get_group_info(new->group_info);
255 get_uid(new->user);
Eric W. Biederman0093ccb2011-11-16 21:52:53 -0800256 get_user_ns(new->user_ns);
David Howellsf1752ee2008-11-14 10:39:17 +1100257
David Howellsbb952bb2008-11-14 10:39:20 +1100258#ifdef CONFIG_KEYS
David Howells3a505972012-10-02 19:24:29 +0100259 key_get(new->session_keyring);
260 key_get(new->process_keyring);
David Howellsd84f4f92008-11-14 10:39:23 +1100261 key_get(new->thread_keyring);
262 key_get(new->request_key_auth);
David Howellsbb952bb2008-11-14 10:39:20 +1100263#endif
264
David Howellsf1752ee2008-11-14 10:39:17 +1100265#ifdef CONFIG_SECURITY
David Howellsd84f4f92008-11-14 10:39:23 +1100266 new->security = NULL;
David Howellsf1752ee2008-11-14 10:39:17 +1100267#endif
268
David Howellsd84f4f92008-11-14 10:39:23 +1100269 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
270 goto error;
David Howellse0e81732009-09-02 09:13:40 +0100271 validate_creds(new);
David Howellsd84f4f92008-11-14 10:39:23 +1100272 return new;
273
274error:
275 abort_creds(new);
276 return NULL;
277}
278EXPORT_SYMBOL(prepare_creds);
279
280/*
David Howellsa6f76f22008-11-14 10:39:24 +1100281 * Prepare credentials for current to perform an execve()
KOSAKI Motohiro9b1bf122010-10-27 15:34:08 -0700282 * - The caller must hold ->cred_guard_mutex
David Howellsa6f76f22008-11-14 10:39:24 +1100283 */
284struct cred *prepare_exec_creds(void)
285{
David Howellsa6f76f22008-11-14 10:39:24 +1100286 struct cred *new;
287
David Howellsa6f76f22008-11-14 10:39:24 +1100288 new = prepare_creds();
David Howells3a505972012-10-02 19:24:29 +0100289 if (!new)
David Howellsa6f76f22008-11-14 10:39:24 +1100290 return new;
David Howellsa6f76f22008-11-14 10:39:24 +1100291
292#ifdef CONFIG_KEYS
293 /* newly exec'd tasks don't get a thread keyring */
294 key_put(new->thread_keyring);
295 new->thread_keyring = NULL;
296
David Howellsa6f76f22008-11-14 10:39:24 +1100297 /* inherit the session keyring; new process keyring */
David Howells3a505972012-10-02 19:24:29 +0100298 key_put(new->process_keyring);
299 new->process_keyring = NULL;
David Howellsa6f76f22008-11-14 10:39:24 +1100300#endif
301
302 return new;
303}
304
305/*
David Howellsd84f4f92008-11-14 10:39:23 +1100306 * Copy credentials for the new process created by fork()
307 *
308 * We share if we can, but under some circumstances we have to generate a new
309 * set.
David Howells3b11a1d2008-11-14 10:39:26 +1100310 *
311 * The new process gets the current process's subjective credentials as its
312 * objective and subjective credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100313 */
314int copy_creds(struct task_struct *p, unsigned long clone_flags)
315{
David Howellsd84f4f92008-11-14 10:39:23 +1100316 struct cred *new;
Serge Hallyn18b6e042008-10-15 16:38:45 -0500317 int ret;
David Howellsd84f4f92008-11-14 10:39:23 +1100318
David Howellsd84f4f92008-11-14 10:39:23 +1100319 if (
320#ifdef CONFIG_KEYS
321 !p->cred->thread_keyring &&
322#endif
323 clone_flags & CLONE_THREAD
324 ) {
David Howells3b11a1d2008-11-14 10:39:26 +1100325 p->real_cred = get_cred(p->cred);
David Howellsd84f4f92008-11-14 10:39:23 +1100326 get_cred(p->cred);
David Howellse0e81732009-09-02 09:13:40 +0100327 alter_cred_subscribers(p->cred, 2);
328 kdebug("share_creds(%p{%d,%d})",
329 p->cred, atomic_read(&p->cred->usage),
330 read_cred_subscribers(p->cred));
David Howellsd84f4f92008-11-14 10:39:23 +1100331 atomic_inc(&p->cred->user->processes);
332 return 0;
David Howellsf1752ee2008-11-14 10:39:17 +1100333 }
334
David Howellsd84f4f92008-11-14 10:39:23 +1100335 new = prepare_creds();
336 if (!new)
337 return -ENOMEM;
David Howellsf1752ee2008-11-14 10:39:17 +1100338
Serge Hallyn18b6e042008-10-15 16:38:45 -0500339 if (clone_flags & CLONE_NEWUSER) {
340 ret = create_user_ns(new);
341 if (ret < 0)
342 goto error_put;
343 }
344
David Howellsd84f4f92008-11-14 10:39:23 +1100345#ifdef CONFIG_KEYS
346 /* new threads get their own thread keyrings if their parent already
347 * had one */
348 if (new->thread_keyring) {
349 key_put(new->thread_keyring);
350 new->thread_keyring = NULL;
351 if (clone_flags & CLONE_THREAD)
352 install_thread_keyring_to_cred(new);
353 }
David Howellsf1752ee2008-11-14 10:39:17 +1100354
David Howells3a505972012-10-02 19:24:29 +0100355 /* The process keyring is only shared between the threads in a process;
356 * anything outside of those threads doesn't inherit.
357 */
David Howellsd84f4f92008-11-14 10:39:23 +1100358 if (!(clone_flags & CLONE_THREAD)) {
David Howells3a505972012-10-02 19:24:29 +0100359 key_put(new->process_keyring);
360 new->process_keyring = NULL;
David Howellsd84f4f92008-11-14 10:39:23 +1100361 }
362#endif
363
364 atomic_inc(&new->user->processes);
David Howells3b11a1d2008-11-14 10:39:26 +1100365 p->cred = p->real_cred = get_cred(new);
David Howellse0e81732009-09-02 09:13:40 +0100366 alter_cred_subscribers(new, 2);
367 validate_creds(new);
David Howellsf1752ee2008-11-14 10:39:17 +1100368 return 0;
Serge Hallyn18b6e042008-10-15 16:38:45 -0500369
370error_put:
371 put_cred(new);
372 return ret;
David Howellsf1752ee2008-11-14 10:39:17 +1100373}
David Howellsd84f4f92008-11-14 10:39:23 +1100374
Eric W. Biedermanaa6d0542012-12-14 08:50:54 -0800375static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
376{
377 const struct user_namespace *set_ns = set->user_ns;
378 const struct user_namespace *subset_ns = subset->user_ns;
379
380 /* If the two credentials are in the same user namespace see if
381 * the capabilities of subset are a subset of set.
382 */
383 if (set_ns == subset_ns)
384 return cap_issubset(subset->cap_permitted, set->cap_permitted);
385
386 /* The credentials are in a different user namespaces
387 * therefore one is a subset of the other only if a set is an
388 * ancestor of subset and set->euid is owner of subset or one
389 * of subsets ancestors.
390 */
391 for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
392 if ((set_ns == subset_ns->parent) &&
393 uid_eq(subset_ns->owner, set->euid))
394 return true;
395 }
396
397 return false;
398}
399
David Howellsd84f4f92008-11-14 10:39:23 +1100400/**
401 * commit_creds - Install new credentials upon the current task
402 * @new: The credentials to be assigned
403 *
404 * Install a new set of credentials to the current task, using RCU to replace
David Howells3b11a1d2008-11-14 10:39:26 +1100405 * the old set. Both the objective and the subjective credentials pointers are
406 * updated. This function may not be called if the subjective credentials are
407 * in an overridden state.
David Howellsd84f4f92008-11-14 10:39:23 +1100408 *
409 * This function eats the caller's reference to the new credentials.
410 *
411 * Always returns 0 thus allowing this function to be tail-called at the end
412 * of, say, sys_setgid().
413 */
414int commit_creds(struct cred *new)
415{
416 struct task_struct *task = current;
David Howellse0e81732009-09-02 09:13:40 +0100417 const struct cred *old = task->real_cred;
David Howellsd84f4f92008-11-14 10:39:23 +1100418
David Howellse0e81732009-09-02 09:13:40 +0100419 kdebug("commit_creds(%p{%d,%d})", new,
420 atomic_read(&new->usage),
421 read_cred_subscribers(new));
422
423 BUG_ON(task->cred != old);
424#ifdef CONFIG_DEBUG_CREDENTIALS
425 BUG_ON(read_cred_subscribers(old) < 2);
426 validate_creds(old);
427 validate_creds(new);
428#endif
David Howellsd84f4f92008-11-14 10:39:23 +1100429 BUG_ON(atomic_read(&new->usage) < 1);
David Howellsd84f4f92008-11-14 10:39:23 +1100430
David Howells3b11a1d2008-11-14 10:39:26 +1100431 get_cred(new); /* we will require a ref for the subj creds too */
432
David Howellsd84f4f92008-11-14 10:39:23 +1100433 /* dumpability changes */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800434 if (!uid_eq(old->euid, new->euid) ||
435 !gid_eq(old->egid, new->egid) ||
436 !uid_eq(old->fsuid, new->fsuid) ||
437 !gid_eq(old->fsgid, new->fsgid) ||
Eric W. Biedermanaa6d0542012-12-14 08:50:54 -0800438 !cred_cap_issubset(old, new)) {
David Howellsb9456372009-01-08 11:18:31 +0000439 if (task->mm)
440 set_dumpable(task->mm, suid_dumpable);
David Howellsd84f4f92008-11-14 10:39:23 +1100441 task->pdeath_signal = 0;
442 smp_wmb();
443 }
444
445 /* alter the thread keyring */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800446 if (!uid_eq(new->fsuid, old->fsuid))
David Howellsd84f4f92008-11-14 10:39:23 +1100447 key_fsuid_changed(task);
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800448 if (!gid_eq(new->fsgid, old->fsgid))
David Howellsd84f4f92008-11-14 10:39:23 +1100449 key_fsgid_changed(task);
450
451 /* do it
Vasiliy Kulikov72fa5992011-08-08 19:02:04 +0400452 * RLIMIT_NPROC limits on user->processes have already been checked
453 * in set_user().
David Howellsd84f4f92008-11-14 10:39:23 +1100454 */
David Howellse0e81732009-09-02 09:13:40 +0100455 alter_cred_subscribers(new, 2);
David Howellsd84f4f92008-11-14 10:39:23 +1100456 if (new->user != old->user)
457 atomic_inc(&new->user->processes);
David Howells3b11a1d2008-11-14 10:39:26 +1100458 rcu_assign_pointer(task->real_cred, new);
David Howellsd84f4f92008-11-14 10:39:23 +1100459 rcu_assign_pointer(task->cred, new);
460 if (new->user != old->user)
461 atomic_dec(&old->user->processes);
David Howellse0e81732009-09-02 09:13:40 +0100462 alter_cred_subscribers(old, -2);
David Howellsd84f4f92008-11-14 10:39:23 +1100463
David Howellsd84f4f92008-11-14 10:39:23 +1100464 /* send notifications */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800465 if (!uid_eq(new->uid, old->uid) ||
466 !uid_eq(new->euid, old->euid) ||
467 !uid_eq(new->suid, old->suid) ||
468 !uid_eq(new->fsuid, old->fsuid))
David Howellsd84f4f92008-11-14 10:39:23 +1100469 proc_id_connector(task, PROC_EVENT_UID);
470
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800471 if (!gid_eq(new->gid, old->gid) ||
472 !gid_eq(new->egid, old->egid) ||
473 !gid_eq(new->sgid, old->sgid) ||
474 !gid_eq(new->fsgid, old->fsgid))
David Howellsd84f4f92008-11-14 10:39:23 +1100475 proc_id_connector(task, PROC_EVENT_GID);
476
David Howells3b11a1d2008-11-14 10:39:26 +1100477 /* release the old obj and subj refs both */
478 put_cred(old);
David Howellsd84f4f92008-11-14 10:39:23 +1100479 put_cred(old);
480 return 0;
481}
482EXPORT_SYMBOL(commit_creds);
483
484/**
485 * abort_creds - Discard a set of credentials and unlock the current task
486 * @new: The credentials that were going to be applied
487 *
488 * Discard a set of credentials that were under construction and unlock the
489 * current task.
490 */
491void abort_creds(struct cred *new)
492{
David Howellse0e81732009-09-02 09:13:40 +0100493 kdebug("abort_creds(%p{%d,%d})", new,
494 atomic_read(&new->usage),
495 read_cred_subscribers(new));
496
497#ifdef CONFIG_DEBUG_CREDENTIALS
498 BUG_ON(read_cred_subscribers(new) != 0);
499#endif
David Howellsd84f4f92008-11-14 10:39:23 +1100500 BUG_ON(atomic_read(&new->usage) < 1);
501 put_cred(new);
502}
503EXPORT_SYMBOL(abort_creds);
504
505/**
David Howells3b11a1d2008-11-14 10:39:26 +1100506 * override_creds - Override the current process's subjective credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100507 * @new: The credentials to be assigned
508 *
David Howells3b11a1d2008-11-14 10:39:26 +1100509 * Install a set of temporary override subjective credentials on the current
510 * process, returning the old set for later reversion.
David Howellsd84f4f92008-11-14 10:39:23 +1100511 */
512const struct cred *override_creds(const struct cred *new)
513{
514 const struct cred *old = current->cred;
515
David Howellse0e81732009-09-02 09:13:40 +0100516 kdebug("override_creds(%p{%d,%d})", new,
517 atomic_read(&new->usage),
518 read_cred_subscribers(new));
519
520 validate_creds(old);
521 validate_creds(new);
522 get_cred(new);
523 alter_cred_subscribers(new, 1);
524 rcu_assign_pointer(current->cred, new);
525 alter_cred_subscribers(old, -1);
526
527 kdebug("override_creds() = %p{%d,%d}", old,
528 atomic_read(&old->usage),
529 read_cred_subscribers(old));
David Howellsd84f4f92008-11-14 10:39:23 +1100530 return old;
531}
532EXPORT_SYMBOL(override_creds);
533
534/**
David Howells3b11a1d2008-11-14 10:39:26 +1100535 * revert_creds - Revert a temporary subjective credentials override
David Howellsd84f4f92008-11-14 10:39:23 +1100536 * @old: The credentials to be restored
537 *
David Howells3b11a1d2008-11-14 10:39:26 +1100538 * Revert a temporary set of override subjective credentials to an old set,
539 * discarding the override set.
David Howellsd84f4f92008-11-14 10:39:23 +1100540 */
541void revert_creds(const struct cred *old)
542{
543 const struct cred *override = current->cred;
544
David Howellse0e81732009-09-02 09:13:40 +0100545 kdebug("revert_creds(%p{%d,%d})", old,
546 atomic_read(&old->usage),
547 read_cred_subscribers(old));
548
549 validate_creds(old);
550 validate_creds(override);
551 alter_cred_subscribers(old, 1);
David Howellsd84f4f92008-11-14 10:39:23 +1100552 rcu_assign_pointer(current->cred, old);
David Howellse0e81732009-09-02 09:13:40 +0100553 alter_cred_subscribers(override, -1);
David Howellsd84f4f92008-11-14 10:39:23 +1100554 put_cred(override);
555}
556EXPORT_SYMBOL(revert_creds);
557
558/*
559 * initialise the credentials stuff
560 */
561void __init cred_init(void)
562{
563 /* allocate a slab in which we can store credentials */
564 cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
565 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
566}
David Howells3a3b7ce2008-11-14 10:39:28 +1100567
568/**
569 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
570 * @daemon: A userspace daemon to be used as a reference
571 *
572 * Prepare a set of credentials for a kernel service. This can then be used to
573 * override a task's own credentials so that work can be done on behalf of that
574 * task that requires a different subjective context.
575 *
576 * @daemon is used to provide a base for the security record, but can be NULL.
577 * If @daemon is supplied, then the security data will be derived from that;
578 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
579 *
580 * The caller may change these controls afterwards if desired.
581 *
582 * Returns the new credentials or NULL if out of memory.
583 *
584 * Does not take, and does not return holding current->cred_replace_mutex.
585 */
586struct cred *prepare_kernel_cred(struct task_struct *daemon)
587{
588 const struct cred *old;
589 struct cred *new;
590
591 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
592 if (!new)
593 return NULL;
594
David Howellse0e81732009-09-02 09:13:40 +0100595 kdebug("prepare_kernel_cred() alloc %p", new);
596
David Howells3a3b7ce2008-11-14 10:39:28 +1100597 if (daemon)
598 old = get_task_cred(daemon);
599 else
600 old = get_cred(&init_cred);
601
David Howellse0e81732009-09-02 09:13:40 +0100602 validate_creds(old);
603
David Howells43529c92009-01-09 16:13:46 +0000604 *new = *old;
Tetsuo Handafb2b2a12011-02-07 13:36:16 +0000605 atomic_set(&new->usage, 1);
606 set_cred_subscribers(new, 0);
David Howells3a3b7ce2008-11-14 10:39:28 +1100607 get_uid(new->user);
Eric W. Biederman0093ccb2011-11-16 21:52:53 -0800608 get_user_ns(new->user_ns);
David Howells3a3b7ce2008-11-14 10:39:28 +1100609 get_group_info(new->group_info);
610
611#ifdef CONFIG_KEYS
David Howells3a505972012-10-02 19:24:29 +0100612 new->session_keyring = NULL;
613 new->process_keyring = NULL;
David Howells3a3b7ce2008-11-14 10:39:28 +1100614 new->thread_keyring = NULL;
David Howells3a505972012-10-02 19:24:29 +0100615 new->request_key_auth = NULL;
David Howells3a3b7ce2008-11-14 10:39:28 +1100616 new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
617#endif
618
619#ifdef CONFIG_SECURITY
620 new->security = NULL;
621#endif
622 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
623 goto error;
624
David Howells3a3b7ce2008-11-14 10:39:28 +1100625 put_cred(old);
David Howellse0e81732009-09-02 09:13:40 +0100626 validate_creds(new);
David Howells3a3b7ce2008-11-14 10:39:28 +1100627 return new;
628
629error:
630 put_cred(new);
David Howells0de33682009-01-09 16:13:41 +0000631 put_cred(old);
David Howells3a3b7ce2008-11-14 10:39:28 +1100632 return NULL;
633}
634EXPORT_SYMBOL(prepare_kernel_cred);
635
636/**
637 * set_security_override - Set the security ID in a set of credentials
638 * @new: The credentials to alter
639 * @secid: The LSM security ID to set
640 *
641 * Set the LSM security ID in a set of credentials so that the subjective
642 * security is overridden when an alternative set of credentials is used.
643 */
644int set_security_override(struct cred *new, u32 secid)
645{
646 return security_kernel_act_as(new, secid);
647}
648EXPORT_SYMBOL(set_security_override);
649
650/**
651 * set_security_override_from_ctx - Set the security ID in a set of credentials
652 * @new: The credentials to alter
653 * @secctx: The LSM security context to generate the security ID from.
654 *
655 * Set the LSM security ID in a set of credentials so that the subjective
656 * security is overridden when an alternative set of credentials is used. The
657 * security ID is specified in string form as a security context to be
658 * interpreted by the LSM.
659 */
660int set_security_override_from_ctx(struct cred *new, const char *secctx)
661{
662 u32 secid;
663 int ret;
664
665 ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
666 if (ret < 0)
667 return ret;
668
669 return set_security_override(new, secid);
670}
671EXPORT_SYMBOL(set_security_override_from_ctx);
672
673/**
674 * set_create_files_as - Set the LSM file create context in a set of credentials
675 * @new: The credentials to alter
676 * @inode: The inode to take the context from
677 *
678 * Change the LSM file creation context in a set of credentials to be the same
679 * as the object context of the specified inode, so that the new inodes have
680 * the same MAC context as that inode.
681 */
682int set_create_files_as(struct cred *new, struct inode *inode)
683{
684 new->fsuid = inode->i_uid;
685 new->fsgid = inode->i_gid;
686 return security_kernel_create_files_as(new, inode);
687}
688EXPORT_SYMBOL(set_create_files_as);
David Howellse0e81732009-09-02 09:13:40 +0100689
690#ifdef CONFIG_DEBUG_CREDENTIALS
691
Andrew Morton74908a02009-09-17 17:47:12 -0700692bool creds_are_invalid(const struct cred *cred)
693{
694 if (cred->magic != CRED_MAGIC)
695 return true;
Andrew Morton74908a02009-09-17 17:47:12 -0700696#ifdef CONFIG_SECURITY_SELINUX
Tetsuo Handa2edeaa32011-02-07 13:36:10 +0000697 /*
698 * cred->security == NULL if security_cred_alloc_blank() or
699 * security_prepare_creds() returned an error.
700 */
701 if (selinux_is_enabled() && cred->security) {
Andrew Morton74908a02009-09-17 17:47:12 -0700702 if ((unsigned long) cred->security < PAGE_SIZE)
703 return true;
704 if ((*(u32 *)cred->security & 0xffffff00) ==
705 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
706 return true;
707 }
708#endif
709 return false;
710}
Randy Dunlap764db032009-09-18 11:06:47 -0700711EXPORT_SYMBOL(creds_are_invalid);
Andrew Morton74908a02009-09-17 17:47:12 -0700712
David Howellse0e81732009-09-02 09:13:40 +0100713/*
714 * dump invalid credentials
715 */
716static void dump_invalid_creds(const struct cred *cred, const char *label,
717 const struct task_struct *tsk)
718{
719 printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
720 label, cred,
721 cred == &init_cred ? "[init]" : "",
722 cred == tsk->real_cred ? "[real]" : "",
723 cred == tsk->cred ? "[eff]" : "");
724 printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
725 cred->magic, cred->put_addr);
726 printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
727 atomic_read(&cred->usage),
728 read_cred_subscribers(cred));
729 printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
Eric W. Biedermanc9235f42012-04-23 17:06:34 -0700730 from_kuid_munged(&init_user_ns, cred->uid),
731 from_kuid_munged(&init_user_ns, cred->euid),
732 from_kuid_munged(&init_user_ns, cred->suid),
733 from_kuid_munged(&init_user_ns, cred->fsuid));
David Howellse0e81732009-09-02 09:13:40 +0100734 printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
Eric W. Biedermanc9235f42012-04-23 17:06:34 -0700735 from_kgid_munged(&init_user_ns, cred->gid),
736 from_kgid_munged(&init_user_ns, cred->egid),
737 from_kgid_munged(&init_user_ns, cred->sgid),
738 from_kgid_munged(&init_user_ns, cred->fsgid));
David Howellse0e81732009-09-02 09:13:40 +0100739#ifdef CONFIG_SECURITY
740 printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
741 if ((unsigned long) cred->security >= PAGE_SIZE &&
742 (((unsigned long) cred->security & 0xffffff00) !=
743 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
744 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
745 ((u32*)cred->security)[0],
746 ((u32*)cred->security)[1]);
747#endif
748}
749
750/*
751 * report use of invalid credentials
752 */
753void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
754{
755 printk(KERN_ERR "CRED: Invalid credentials\n");
756 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
757 dump_invalid_creds(cred, "Specified", current);
758 BUG();
759}
760EXPORT_SYMBOL(__invalid_creds);
761
762/*
763 * check the credentials on a process
764 */
765void __validate_process_creds(struct task_struct *tsk,
766 const char *file, unsigned line)
767{
768 if (tsk->cred == tsk->real_cred) {
769 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
770 creds_are_invalid(tsk->cred)))
771 goto invalid_creds;
772 } else {
773 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
774 read_cred_subscribers(tsk->cred) < 1 ||
775 creds_are_invalid(tsk->real_cred) ||
776 creds_are_invalid(tsk->cred)))
777 goto invalid_creds;
778 }
779 return;
780
781invalid_creds:
782 printk(KERN_ERR "CRED: Invalid process credentials\n");
783 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
784
785 dump_invalid_creds(tsk->real_cred, "Real", tsk);
786 if (tsk->cred != tsk->real_cred)
787 dump_invalid_creds(tsk->cred, "Effective", tsk);
788 else
789 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
790 BUG();
791}
792EXPORT_SYMBOL(__validate_process_creds);
793
794/*
795 * check creds for do_exit()
796 */
797void validate_creds_for_do_exit(struct task_struct *tsk)
798{
799 kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
800 tsk->real_cred, tsk->cred,
801 atomic_read(&tsk->cred->usage),
802 read_cred_subscribers(tsk->cred));
803
804 __validate_process_creds(tsk, __FILE__, __LINE__);
805}
806
807#endif /* CONFIG_DEBUG_CREDENTIALS */