blob: ecf03657e71c9c2eb959cc2ee46cee0414f5f0ca [file] [log] [blame]
Kees Cookaf777cd2017-05-13 04:51:40 -07001/* Task credentials management - see Documentation/security/credentials.rst
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>
Ingo Molnarf7ccbae2017-02-08 18:51:30 +010015#include <linux/sched/coredump.h>
David Howellsf1752ee2008-11-14 10:39:17 +110016#include <linux/key.h>
17#include <linux/keyctl.h>
18#include <linux/init_task.h>
19#include <linux/security.h>
Al Viro40401532012-02-13 03:58:52 +000020#include <linux/binfmts.h>
David Howellsd84f4f92008-11-14 10:39:23 +110021#include <linux/cn_proc.h>
David Howellsd84f4f92008-11-14 10:39:23 +110022
David Howellse0e81732009-09-02 09:13:40 +010023#if 0
Joe Perches52aa8532015-09-09 15:36:09 -070024#define kdebug(FMT, ...) \
25 printk("[%-5.5s%5u] " FMT "\n", \
26 current->comm, current->pid, ##__VA_ARGS__)
David Howellse0e81732009-09-02 09:13:40 +010027#else
Joe Perches52aa8532015-09-09 15:36:09 -070028#define kdebug(FMT, ...) \
29do { \
30 if (0) \
31 no_printk("[%-5.5s%5u] " FMT "\n", \
32 current->comm, current->pid, ##__VA_ARGS__); \
33} while (0)
David Howellse0e81732009-09-02 09:13:40 +010034#endif
35
David Howellsd84f4f92008-11-14 10:39:23 +110036static struct kmem_cache *cred_jar;
David Howellsf1752ee2008-11-14 10:39:17 +110037
Iulia Manda28138932015-04-15 16:16:41 -070038/* init to 2 - one for init_task, one to ensure it is never freed */
39struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
40
David Howellsf1752ee2008-11-14 10:39:17 +110041/*
42 * The initial credentials for the initial task
43 */
44struct cred init_cred = {
David Howells3b11a1d2008-11-14 10:39:26 +110045 .usage = ATOMIC_INIT(4),
David Howellse0e81732009-09-02 09:13:40 +010046#ifdef CONFIG_DEBUG_CREDENTIALS
47 .subscribers = ATOMIC_INIT(2),
48 .magic = CRED_MAGIC,
49#endif
Eric W. Biederman078de5f2012-02-08 07:00:08 -080050 .uid = GLOBAL_ROOT_UID,
51 .gid = GLOBAL_ROOT_GID,
52 .suid = GLOBAL_ROOT_UID,
53 .sgid = GLOBAL_ROOT_GID,
54 .euid = GLOBAL_ROOT_UID,
55 .egid = GLOBAL_ROOT_GID,
56 .fsuid = GLOBAL_ROOT_UID,
57 .fsgid = GLOBAL_ROOT_GID,
David Howellsf1752ee2008-11-14 10:39:17 +110058 .securebits = SECUREBITS_DEFAULT,
Eric Parisa3232d22011-04-01 17:08:45 -040059 .cap_inheritable = CAP_EMPTY_SET,
David Howellsf1752ee2008-11-14 10:39:17 +110060 .cap_permitted = CAP_FULL_SET,
Eric Parisa3232d22011-04-01 17:08:45 -040061 .cap_effective = CAP_FULL_SET,
62 .cap_bset = CAP_FULL_SET,
David Howellsf1752ee2008-11-14 10:39:17 +110063 .user = INIT_USER,
Serge E. Hallyn47a150e2011-05-13 04:27:54 +010064 .user_ns = &init_user_ns,
David Howellsf1752ee2008-11-14 10:39:17 +110065 .group_info = &init_groups,
66};
67
David Howellse0e81732009-09-02 09:13:40 +010068static 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
75static 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
84static 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
David Howellsf1752ee2008-11-14 10:39:17 +110093/*
94 * The RCU callback to actually dispose of a set of credentials
95 */
96static void put_cred_rcu(struct rcu_head *rcu)
97{
98 struct cred *cred = container_of(rcu, struct cred, rcu);
99
David Howellse0e81732009-09-02 09:13:40 +0100100 kdebug("put_cred_rcu(%p)", cred);
101
102#ifdef CONFIG_DEBUG_CREDENTIALS
103 if (cred->magic != CRED_MAGIC_DEAD ||
104 atomic_read(&cred->usage) != 0 ||
105 read_cred_subscribers(cred) != 0)
106 panic("CRED: put_cred_rcu() sees %p with"
107 " mag %x, put %p, usage %d, subscr %d\n",
108 cred, cred->magic, cred->put_addr,
109 atomic_read(&cred->usage),
110 read_cred_subscribers(cred));
111#else
David Howellsd84f4f92008-11-14 10:39:23 +1100112 if (atomic_read(&cred->usage) != 0)
113 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
114 cred, atomic_read(&cred->usage));
David Howellse0e81732009-09-02 09:13:40 +0100115#endif
David Howellsf1752ee2008-11-14 10:39:17 +1100116
David Howellsd84f4f92008-11-14 10:39:23 +1100117 security_cred_free(cred);
David Howells3a505972012-10-02 19:24:29 +0100118 key_put(cred->session_keyring);
119 key_put(cred->process_keyring);
David Howellsf1752ee2008-11-14 10:39:17 +1100120 key_put(cred->thread_keyring);
121 key_put(cred->request_key_auth);
David Howells4a5d6ba2009-09-14 12:45:39 +0100122 if (cred->group_info)
123 put_group_info(cred->group_info);
David Howellsf1752ee2008-11-14 10:39:17 +1100124 free_uid(cred->user);
Eric W. Biederman0093ccb2011-11-16 21:52:53 -0800125 put_user_ns(cred->user_ns);
David Howellsd84f4f92008-11-14 10:39:23 +1100126 kmem_cache_free(cred_jar, cred);
David Howellsf1752ee2008-11-14 10:39:17 +1100127}
128
129/**
130 * __put_cred - Destroy a set of credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100131 * @cred: The record to release
David Howellsf1752ee2008-11-14 10:39:17 +1100132 *
133 * Destroy a set of credentials on which no references remain.
134 */
135void __put_cred(struct cred *cred)
136{
David Howellse0e81732009-09-02 09:13:40 +0100137 kdebug("__put_cred(%p{%d,%d})", cred,
138 atomic_read(&cred->usage),
139 read_cred_subscribers(cred));
140
David Howellsd84f4f92008-11-14 10:39:23 +1100141 BUG_ON(atomic_read(&cred->usage) != 0);
David Howellse0e81732009-09-02 09:13:40 +0100142#ifdef CONFIG_DEBUG_CREDENTIALS
143 BUG_ON(read_cred_subscribers(cred) != 0);
144 cred->magic = CRED_MAGIC_DEAD;
145 cred->put_addr = __builtin_return_address(0);
146#endif
147 BUG_ON(cred == current->cred);
148 BUG_ON(cred == current->real_cred);
David Howellsd84f4f92008-11-14 10:39:23 +1100149
David Howellsf1752ee2008-11-14 10:39:17 +1100150 call_rcu(&cred->rcu, put_cred_rcu);
151}
152EXPORT_SYMBOL(__put_cred);
153
David Howellse0e81732009-09-02 09:13:40 +0100154/*
155 * Clean up a task's credentials when it exits
156 */
157void exit_creds(struct task_struct *tsk)
158{
159 struct cred *cred;
160
161 kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
162 atomic_read(&tsk->cred->usage),
163 read_cred_subscribers(tsk->cred));
164
165 cred = (struct cred *) tsk->real_cred;
166 tsk->real_cred = NULL;
167 validate_creds(cred);
168 alter_cred_subscribers(cred, -1);
169 put_cred(cred);
170
171 cred = (struct cred *) tsk->cred;
172 tsk->cred = NULL;
173 validate_creds(cred);
174 alter_cred_subscribers(cred, -1);
175 put_cred(cred);
David Howellsee18d642009-09-02 09:14:21 +0100176}
177
David Howellsde09a972010-07-29 12:45:49 +0100178/**
179 * get_task_cred - Get another task's objective credentials
180 * @task: The task to query
181 *
182 * Get the objective credentials of a task, pinning them so that they can't go
183 * away. Accessing a task's credentials directly is not permitted.
184 *
185 * The caller must also make sure task doesn't get deleted, either by holding a
186 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
187 */
188const struct cred *get_task_cred(struct task_struct *task)
189{
190 const struct cred *cred;
191
192 rcu_read_lock();
193
194 do {
195 cred = __task_cred((task));
196 BUG_ON(!cred);
197 } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
198
199 rcu_read_unlock();
200 return cred;
201}
202
David Howellsee18d642009-09-02 09:14:21 +0100203/*
204 * Allocate blank credentials, such that the credentials can be filled in at a
205 * later date without risk of ENOMEM.
206 */
207struct cred *cred_alloc_blank(void)
208{
209 struct cred *new;
210
211 new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
212 if (!new)
213 return NULL;
214
David Howellsee18d642009-09-02 09:14:21 +0100215 atomic_set(&new->usage, 1);
Tetsuo Handa2edeaa32011-02-07 13:36:10 +0000216#ifdef CONFIG_DEBUG_CREDENTIALS
217 new->magic = CRED_MAGIC;
218#endif
David Howellsee18d642009-09-02 09:14:21 +0100219
220 if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
221 goto error;
222
David Howellsee18d642009-09-02 09:14:21 +0100223 return new;
224
225error:
226 abort_creds(new);
227 return NULL;
David Howellse0e81732009-09-02 09:13:40 +0100228}
229
David Howellsd84f4f92008-11-14 10:39:23 +1100230/**
231 * prepare_creds - Prepare a new set of credentials for modification
232 *
233 * Prepare a new set of task credentials for modification. A task's creds
234 * shouldn't generally be modified directly, therefore this function is used to
235 * prepare a new copy, which the caller then modifies and then commits by
236 * calling commit_creds().
237 *
David Howells3b11a1d2008-11-14 10:39:26 +1100238 * Preparation involves making a copy of the objective creds for modification.
239 *
David Howellsd84f4f92008-11-14 10:39:23 +1100240 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
241 *
242 * Call commit_creds() or abort_creds() to clean up.
David Howellsf1752ee2008-11-14 10:39:17 +1100243 */
David Howellsd84f4f92008-11-14 10:39:23 +1100244struct cred *prepare_creds(void)
David Howellsf1752ee2008-11-14 10:39:17 +1100245{
David Howellsd84f4f92008-11-14 10:39:23 +1100246 struct task_struct *task = current;
247 const struct cred *old;
248 struct cred *new;
David Howellsf1752ee2008-11-14 10:39:17 +1100249
David Howellse0e81732009-09-02 09:13:40 +0100250 validate_process_creds();
David Howellsd84f4f92008-11-14 10:39:23 +1100251
252 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
253 if (!new)
254 return NULL;
255
David Howellse0e81732009-09-02 09:13:40 +0100256 kdebug("prepare_creds() alloc %p", new);
257
David Howellsd84f4f92008-11-14 10:39:23 +1100258 old = task->cred;
259 memcpy(new, old, sizeof(struct cred));
260
261 atomic_set(&new->usage, 1);
David Howellse0e81732009-09-02 09:13:40 +0100262 set_cred_subscribers(new, 0);
David Howellsd84f4f92008-11-14 10:39:23 +1100263 get_group_info(new->group_info);
264 get_uid(new->user);
Eric W. Biederman0093ccb2011-11-16 21:52:53 -0800265 get_user_ns(new->user_ns);
David Howellsf1752ee2008-11-14 10:39:17 +1100266
David Howellsbb952bb2008-11-14 10:39:20 +1100267#ifdef CONFIG_KEYS
David Howells3a505972012-10-02 19:24:29 +0100268 key_get(new->session_keyring);
269 key_get(new->process_keyring);
David Howellsd84f4f92008-11-14 10:39:23 +1100270 key_get(new->thread_keyring);
271 key_get(new->request_key_auth);
David Howellsbb952bb2008-11-14 10:39:20 +1100272#endif
273
David Howellsf1752ee2008-11-14 10:39:17 +1100274#ifdef CONFIG_SECURITY
David Howellsd84f4f92008-11-14 10:39:23 +1100275 new->security = NULL;
David Howellsf1752ee2008-11-14 10:39:17 +1100276#endif
277
David Howellsd84f4f92008-11-14 10:39:23 +1100278 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
279 goto error;
David Howellse0e81732009-09-02 09:13:40 +0100280 validate_creds(new);
David Howellsd84f4f92008-11-14 10:39:23 +1100281 return new;
282
283error:
284 abort_creds(new);
285 return NULL;
286}
287EXPORT_SYMBOL(prepare_creds);
288
289/*
David Howellsa6f76f22008-11-14 10:39:24 +1100290 * Prepare credentials for current to perform an execve()
KOSAKI Motohiro9b1bf122010-10-27 15:34:08 -0700291 * - The caller must hold ->cred_guard_mutex
David Howellsa6f76f22008-11-14 10:39:24 +1100292 */
293struct cred *prepare_exec_creds(void)
294{
David Howellsa6f76f22008-11-14 10:39:24 +1100295 struct cred *new;
296
David Howellsa6f76f22008-11-14 10:39:24 +1100297 new = prepare_creds();
David Howells3a505972012-10-02 19:24:29 +0100298 if (!new)
David Howellsa6f76f22008-11-14 10:39:24 +1100299 return new;
David Howellsa6f76f22008-11-14 10:39:24 +1100300
301#ifdef CONFIG_KEYS
302 /* newly exec'd tasks don't get a thread keyring */
303 key_put(new->thread_keyring);
304 new->thread_keyring = NULL;
305
David Howellsa6f76f22008-11-14 10:39:24 +1100306 /* inherit the session keyring; new process keyring */
David Howells3a505972012-10-02 19:24:29 +0100307 key_put(new->process_keyring);
308 new->process_keyring = NULL;
David Howellsa6f76f22008-11-14 10:39:24 +1100309#endif
310
311 return new;
312}
313
314/*
David Howellsd84f4f92008-11-14 10:39:23 +1100315 * Copy credentials for the new process created by fork()
316 *
317 * We share if we can, but under some circumstances we have to generate a new
318 * set.
David Howells3b11a1d2008-11-14 10:39:26 +1100319 *
320 * The new process gets the current process's subjective credentials as its
321 * objective and subjective credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100322 */
323int copy_creds(struct task_struct *p, unsigned long clone_flags)
324{
David Howellsd84f4f92008-11-14 10:39:23 +1100325 struct cred *new;
Serge Hallyn18b6e042008-10-15 16:38:45 -0500326 int ret;
David Howellsd84f4f92008-11-14 10:39:23 +1100327
David Howellsd84f4f92008-11-14 10:39:23 +1100328 if (
329#ifdef CONFIG_KEYS
330 !p->cred->thread_keyring &&
331#endif
332 clone_flags & CLONE_THREAD
333 ) {
David Howells3b11a1d2008-11-14 10:39:26 +1100334 p->real_cred = get_cred(p->cred);
David Howellsd84f4f92008-11-14 10:39:23 +1100335 get_cred(p->cred);
David Howellse0e81732009-09-02 09:13:40 +0100336 alter_cred_subscribers(p->cred, 2);
337 kdebug("share_creds(%p{%d,%d})",
338 p->cred, atomic_read(&p->cred->usage),
339 read_cred_subscribers(p->cred));
David Howellsd84f4f92008-11-14 10:39:23 +1100340 atomic_inc(&p->cred->user->processes);
341 return 0;
David Howellsf1752ee2008-11-14 10:39:17 +1100342 }
343
David Howellsd84f4f92008-11-14 10:39:23 +1100344 new = prepare_creds();
345 if (!new)
346 return -ENOMEM;
David Howellsf1752ee2008-11-14 10:39:17 +1100347
Serge Hallyn18b6e042008-10-15 16:38:45 -0500348 if (clone_flags & CLONE_NEWUSER) {
349 ret = create_user_ns(new);
350 if (ret < 0)
351 goto error_put;
352 }
353
David Howellsd84f4f92008-11-14 10:39:23 +1100354#ifdef CONFIG_KEYS
355 /* new threads get their own thread keyrings if their parent already
356 * had one */
357 if (new->thread_keyring) {
358 key_put(new->thread_keyring);
359 new->thread_keyring = NULL;
360 if (clone_flags & CLONE_THREAD)
361 install_thread_keyring_to_cred(new);
362 }
David Howellsf1752ee2008-11-14 10:39:17 +1100363
David Howells3a505972012-10-02 19:24:29 +0100364 /* The process keyring is only shared between the threads in a process;
365 * anything outside of those threads doesn't inherit.
366 */
David Howellsd84f4f92008-11-14 10:39:23 +1100367 if (!(clone_flags & CLONE_THREAD)) {
David Howells3a505972012-10-02 19:24:29 +0100368 key_put(new->process_keyring);
369 new->process_keyring = NULL;
David Howellsd84f4f92008-11-14 10:39:23 +1100370 }
371#endif
372
373 atomic_inc(&new->user->processes);
David Howells3b11a1d2008-11-14 10:39:26 +1100374 p->cred = p->real_cred = get_cred(new);
David Howellse0e81732009-09-02 09:13:40 +0100375 alter_cred_subscribers(new, 2);
376 validate_creds(new);
David Howellsf1752ee2008-11-14 10:39:17 +1100377 return 0;
Serge Hallyn18b6e042008-10-15 16:38:45 -0500378
379error_put:
380 put_cred(new);
381 return ret;
David Howellsf1752ee2008-11-14 10:39:17 +1100382}
David Howellsd84f4f92008-11-14 10:39:23 +1100383
Eric W. Biedermanaa6d0542012-12-14 08:50:54 -0800384static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
385{
386 const struct user_namespace *set_ns = set->user_ns;
387 const struct user_namespace *subset_ns = subset->user_ns;
388
389 /* If the two credentials are in the same user namespace see if
390 * the capabilities of subset are a subset of set.
391 */
392 if (set_ns == subset_ns)
393 return cap_issubset(subset->cap_permitted, set->cap_permitted);
394
395 /* The credentials are in a different user namespaces
396 * therefore one is a subset of the other only if a set is an
397 * ancestor of subset and set->euid is owner of subset or one
398 * of subsets ancestors.
399 */
400 for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
401 if ((set_ns == subset_ns->parent) &&
402 uid_eq(subset_ns->owner, set->euid))
403 return true;
404 }
405
406 return false;
407}
408
David Howellsd84f4f92008-11-14 10:39:23 +1100409/**
410 * commit_creds - Install new credentials upon the current task
411 * @new: The credentials to be assigned
412 *
413 * Install a new set of credentials to the current task, using RCU to replace
David Howells3b11a1d2008-11-14 10:39:26 +1100414 * the old set. Both the objective and the subjective credentials pointers are
415 * updated. This function may not be called if the subjective credentials are
416 * in an overridden state.
David Howellsd84f4f92008-11-14 10:39:23 +1100417 *
418 * This function eats the caller's reference to the new credentials.
419 *
420 * Always returns 0 thus allowing this function to be tail-called at the end
421 * of, say, sys_setgid().
422 */
423int commit_creds(struct cred *new)
424{
425 struct task_struct *task = current;
David Howellse0e81732009-09-02 09:13:40 +0100426 const struct cred *old = task->real_cred;
David Howellsd84f4f92008-11-14 10:39:23 +1100427
David Howellse0e81732009-09-02 09:13:40 +0100428 kdebug("commit_creds(%p{%d,%d})", new,
429 atomic_read(&new->usage),
430 read_cred_subscribers(new));
431
432 BUG_ON(task->cred != old);
433#ifdef CONFIG_DEBUG_CREDENTIALS
434 BUG_ON(read_cred_subscribers(old) < 2);
435 validate_creds(old);
436 validate_creds(new);
437#endif
David Howellsd84f4f92008-11-14 10:39:23 +1100438 BUG_ON(atomic_read(&new->usage) < 1);
David Howellsd84f4f92008-11-14 10:39:23 +1100439
David Howells3b11a1d2008-11-14 10:39:26 +1100440 get_cred(new); /* we will require a ref for the subj creds too */
441
David Howellsd84f4f92008-11-14 10:39:23 +1100442 /* dumpability changes */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800443 if (!uid_eq(old->euid, new->euid) ||
444 !gid_eq(old->egid, new->egid) ||
445 !uid_eq(old->fsuid, new->fsuid) ||
446 !gid_eq(old->fsgid, new->fsgid) ||
Eric W. Biedermanaa6d0542012-12-14 08:50:54 -0800447 !cred_cap_issubset(old, new)) {
David Howellsb9456372009-01-08 11:18:31 +0000448 if (task->mm)
449 set_dumpable(task->mm, suid_dumpable);
David Howellsd84f4f92008-11-14 10:39:23 +1100450 task->pdeath_signal = 0;
451 smp_wmb();
452 }
453
454 /* alter the thread keyring */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800455 if (!uid_eq(new->fsuid, old->fsuid))
David Howellsd84f4f92008-11-14 10:39:23 +1100456 key_fsuid_changed(task);
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800457 if (!gid_eq(new->fsgid, old->fsgid))
David Howellsd84f4f92008-11-14 10:39:23 +1100458 key_fsgid_changed(task);
459
460 /* do it
Vasiliy Kulikov72fa5992011-08-08 19:02:04 +0400461 * RLIMIT_NPROC limits on user->processes have already been checked
462 * in set_user().
David Howellsd84f4f92008-11-14 10:39:23 +1100463 */
David Howellse0e81732009-09-02 09:13:40 +0100464 alter_cred_subscribers(new, 2);
David Howellsd84f4f92008-11-14 10:39:23 +1100465 if (new->user != old->user)
466 atomic_inc(&new->user->processes);
David Howells3b11a1d2008-11-14 10:39:26 +1100467 rcu_assign_pointer(task->real_cred, new);
David Howellsd84f4f92008-11-14 10:39:23 +1100468 rcu_assign_pointer(task->cred, new);
469 if (new->user != old->user)
470 atomic_dec(&old->user->processes);
David Howellse0e81732009-09-02 09:13:40 +0100471 alter_cred_subscribers(old, -2);
David Howellsd84f4f92008-11-14 10:39:23 +1100472
David Howellsd84f4f92008-11-14 10:39:23 +1100473 /* send notifications */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800474 if (!uid_eq(new->uid, old->uid) ||
475 !uid_eq(new->euid, old->euid) ||
476 !uid_eq(new->suid, old->suid) ||
477 !uid_eq(new->fsuid, old->fsuid))
David Howellsd84f4f92008-11-14 10:39:23 +1100478 proc_id_connector(task, PROC_EVENT_UID);
479
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800480 if (!gid_eq(new->gid, old->gid) ||
481 !gid_eq(new->egid, old->egid) ||
482 !gid_eq(new->sgid, old->sgid) ||
483 !gid_eq(new->fsgid, old->fsgid))
David Howellsd84f4f92008-11-14 10:39:23 +1100484 proc_id_connector(task, PROC_EVENT_GID);
485
David Howells3b11a1d2008-11-14 10:39:26 +1100486 /* release the old obj and subj refs both */
487 put_cred(old);
David Howellsd84f4f92008-11-14 10:39:23 +1100488 put_cred(old);
489 return 0;
490}
491EXPORT_SYMBOL(commit_creds);
492
493/**
494 * abort_creds - Discard a set of credentials and unlock the current task
495 * @new: The credentials that were going to be applied
496 *
497 * Discard a set of credentials that were under construction and unlock the
498 * current task.
499 */
500void abort_creds(struct cred *new)
501{
David Howellse0e81732009-09-02 09:13:40 +0100502 kdebug("abort_creds(%p{%d,%d})", new,
503 atomic_read(&new->usage),
504 read_cred_subscribers(new));
505
506#ifdef CONFIG_DEBUG_CREDENTIALS
507 BUG_ON(read_cred_subscribers(new) != 0);
508#endif
David Howellsd84f4f92008-11-14 10:39:23 +1100509 BUG_ON(atomic_read(&new->usage) < 1);
510 put_cred(new);
511}
512EXPORT_SYMBOL(abort_creds);
513
514/**
David Howells3b11a1d2008-11-14 10:39:26 +1100515 * override_creds - Override the current process's subjective credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100516 * @new: The credentials to be assigned
517 *
David Howells3b11a1d2008-11-14 10:39:26 +1100518 * Install a set of temporary override subjective credentials on the current
519 * process, returning the old set for later reversion.
David Howellsd84f4f92008-11-14 10:39:23 +1100520 */
521const struct cred *override_creds(const struct cred *new)
522{
523 const struct cred *old = current->cred;
524
David Howellse0e81732009-09-02 09:13:40 +0100525 kdebug("override_creds(%p{%d,%d})", new,
526 atomic_read(&new->usage),
527 read_cred_subscribers(new));
528
529 validate_creds(old);
530 validate_creds(new);
531 get_cred(new);
532 alter_cred_subscribers(new, 1);
533 rcu_assign_pointer(current->cred, new);
534 alter_cred_subscribers(old, -1);
535
536 kdebug("override_creds() = %p{%d,%d}", old,
537 atomic_read(&old->usage),
538 read_cred_subscribers(old));
David Howellsd84f4f92008-11-14 10:39:23 +1100539 return old;
540}
541EXPORT_SYMBOL(override_creds);
542
543/**
David Howells3b11a1d2008-11-14 10:39:26 +1100544 * revert_creds - Revert a temporary subjective credentials override
David Howellsd84f4f92008-11-14 10:39:23 +1100545 * @old: The credentials to be restored
546 *
David Howells3b11a1d2008-11-14 10:39:26 +1100547 * Revert a temporary set of override subjective credentials to an old set,
548 * discarding the override set.
David Howellsd84f4f92008-11-14 10:39:23 +1100549 */
550void revert_creds(const struct cred *old)
551{
552 const struct cred *override = current->cred;
553
David Howellse0e81732009-09-02 09:13:40 +0100554 kdebug("revert_creds(%p{%d,%d})", old,
555 atomic_read(&old->usage),
556 read_cred_subscribers(old));
557
558 validate_creds(old);
559 validate_creds(override);
560 alter_cred_subscribers(old, 1);
David Howellsd84f4f92008-11-14 10:39:23 +1100561 rcu_assign_pointer(current->cred, old);
David Howellse0e81732009-09-02 09:13:40 +0100562 alter_cred_subscribers(override, -1);
David Howellsd84f4f92008-11-14 10:39:23 +1100563 put_cred(override);
564}
565EXPORT_SYMBOL(revert_creds);
566
567/*
568 * initialise the credentials stuff
569 */
570void __init cred_init(void)
571{
572 /* allocate a slab in which we can store credentials */
Vladimir Davydov5d097052016-01-14 15:18:21 -0800573 cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
574 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
David Howellsd84f4f92008-11-14 10:39:23 +1100575}
David Howells3a3b7ce2008-11-14 10:39:28 +1100576
577/**
578 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
579 * @daemon: A userspace daemon to be used as a reference
580 *
581 * Prepare a set of credentials for a kernel service. This can then be used to
582 * override a task's own credentials so that work can be done on behalf of that
583 * task that requires a different subjective context.
584 *
585 * @daemon is used to provide a base for the security record, but can be NULL.
586 * If @daemon is supplied, then the security data will be derived from that;
587 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
588 *
589 * The caller may change these controls afterwards if desired.
590 *
591 * Returns the new credentials or NULL if out of memory.
592 *
593 * Does not take, and does not return holding current->cred_replace_mutex.
594 */
595struct cred *prepare_kernel_cred(struct task_struct *daemon)
596{
597 const struct cred *old;
598 struct cred *new;
599
600 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
601 if (!new)
602 return NULL;
603
David Howellse0e81732009-09-02 09:13:40 +0100604 kdebug("prepare_kernel_cred() alloc %p", new);
605
David Howells3a3b7ce2008-11-14 10:39:28 +1100606 if (daemon)
607 old = get_task_cred(daemon);
608 else
609 old = get_cred(&init_cred);
610
David Howellse0e81732009-09-02 09:13:40 +0100611 validate_creds(old);
612
David Howells43529c92009-01-09 16:13:46 +0000613 *new = *old;
Tetsuo Handafb2b2a12011-02-07 13:36:16 +0000614 atomic_set(&new->usage, 1);
615 set_cred_subscribers(new, 0);
David Howells3a3b7ce2008-11-14 10:39:28 +1100616 get_uid(new->user);
Eric W. Biederman0093ccb2011-11-16 21:52:53 -0800617 get_user_ns(new->user_ns);
David Howells3a3b7ce2008-11-14 10:39:28 +1100618 get_group_info(new->group_info);
619
620#ifdef CONFIG_KEYS
David Howells3a505972012-10-02 19:24:29 +0100621 new->session_keyring = NULL;
622 new->process_keyring = NULL;
David Howells3a3b7ce2008-11-14 10:39:28 +1100623 new->thread_keyring = NULL;
David Howells3a505972012-10-02 19:24:29 +0100624 new->request_key_auth = NULL;
David Howells3a3b7ce2008-11-14 10:39:28 +1100625 new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
626#endif
627
628#ifdef CONFIG_SECURITY
629 new->security = NULL;
630#endif
631 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
632 goto error;
633
David Howells3a3b7ce2008-11-14 10:39:28 +1100634 put_cred(old);
David Howellse0e81732009-09-02 09:13:40 +0100635 validate_creds(new);
David Howells3a3b7ce2008-11-14 10:39:28 +1100636 return new;
637
638error:
639 put_cred(new);
David Howells0de33682009-01-09 16:13:41 +0000640 put_cred(old);
David Howells3a3b7ce2008-11-14 10:39:28 +1100641 return NULL;
642}
643EXPORT_SYMBOL(prepare_kernel_cred);
644
645/**
646 * set_security_override - Set the security ID in a set of credentials
647 * @new: The credentials to alter
648 * @secid: The LSM security ID to set
649 *
650 * Set the LSM security ID in a set of credentials so that the subjective
651 * security is overridden when an alternative set of credentials is used.
652 */
653int set_security_override(struct cred *new, u32 secid)
654{
655 return security_kernel_act_as(new, secid);
656}
657EXPORT_SYMBOL(set_security_override);
658
659/**
660 * set_security_override_from_ctx - Set the security ID in a set of credentials
661 * @new: The credentials to alter
662 * @secctx: The LSM security context to generate the security ID from.
663 *
664 * Set the LSM security ID in a set of credentials so that the subjective
665 * security is overridden when an alternative set of credentials is used. The
666 * security ID is specified in string form as a security context to be
667 * interpreted by the LSM.
668 */
669int set_security_override_from_ctx(struct cred *new, const char *secctx)
670{
671 u32 secid;
672 int ret;
673
674 ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
675 if (ret < 0)
676 return ret;
677
678 return set_security_override(new, secid);
679}
680EXPORT_SYMBOL(set_security_override_from_ctx);
681
682/**
683 * set_create_files_as - Set the LSM file create context in a set of credentials
684 * @new: The credentials to alter
685 * @inode: The inode to take the context from
686 *
687 * Change the LSM file creation context in a set of credentials to be the same
688 * as the object context of the specified inode, so that the new inodes have
689 * the same MAC context as that inode.
690 */
691int set_create_files_as(struct cred *new, struct inode *inode)
692{
Seth Forshee5f65e5c2016-04-26 14:36:24 -0500693 if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
694 return -EINVAL;
David Howells3a3b7ce2008-11-14 10:39:28 +1100695 new->fsuid = inode->i_uid;
696 new->fsgid = inode->i_gid;
697 return security_kernel_create_files_as(new, inode);
698}
699EXPORT_SYMBOL(set_create_files_as);
David Howellse0e81732009-09-02 09:13:40 +0100700
701#ifdef CONFIG_DEBUG_CREDENTIALS
702
Andrew Morton74908a02009-09-17 17:47:12 -0700703bool creds_are_invalid(const struct cred *cred)
704{
705 if (cred->magic != CRED_MAGIC)
706 return true;
Andrew Morton74908a02009-09-17 17:47:12 -0700707#ifdef CONFIG_SECURITY_SELINUX
Tetsuo Handa2edeaa32011-02-07 13:36:10 +0000708 /*
709 * cred->security == NULL if security_cred_alloc_blank() or
710 * security_prepare_creds() returned an error.
711 */
712 if (selinux_is_enabled() && cred->security) {
Andrew Morton74908a02009-09-17 17:47:12 -0700713 if ((unsigned long) cred->security < PAGE_SIZE)
714 return true;
715 if ((*(u32 *)cred->security & 0xffffff00) ==
716 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
717 return true;
718 }
719#endif
720 return false;
721}
Randy Dunlap764db032009-09-18 11:06:47 -0700722EXPORT_SYMBOL(creds_are_invalid);
Andrew Morton74908a02009-09-17 17:47:12 -0700723
David Howellse0e81732009-09-02 09:13:40 +0100724/*
725 * dump invalid credentials
726 */
727static void dump_invalid_creds(const struct cred *cred, const char *label,
728 const struct task_struct *tsk)
729{
730 printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
731 label, cred,
732 cred == &init_cred ? "[init]" : "",
733 cred == tsk->real_cred ? "[real]" : "",
734 cred == tsk->cred ? "[eff]" : "");
735 printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
736 cred->magic, cred->put_addr);
737 printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
738 atomic_read(&cred->usage),
739 read_cred_subscribers(cred));
740 printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
Eric W. Biedermanc9235f42012-04-23 17:06:34 -0700741 from_kuid_munged(&init_user_ns, cred->uid),
742 from_kuid_munged(&init_user_ns, cred->euid),
743 from_kuid_munged(&init_user_ns, cred->suid),
744 from_kuid_munged(&init_user_ns, cred->fsuid));
David Howellse0e81732009-09-02 09:13:40 +0100745 printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
Eric W. Biedermanc9235f42012-04-23 17:06:34 -0700746 from_kgid_munged(&init_user_ns, cred->gid),
747 from_kgid_munged(&init_user_ns, cred->egid),
748 from_kgid_munged(&init_user_ns, cred->sgid),
749 from_kgid_munged(&init_user_ns, cred->fsgid));
David Howellse0e81732009-09-02 09:13:40 +0100750#ifdef CONFIG_SECURITY
751 printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
752 if ((unsigned long) cred->security >= PAGE_SIZE &&
753 (((unsigned long) cred->security & 0xffffff00) !=
754 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
755 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
756 ((u32*)cred->security)[0],
757 ((u32*)cred->security)[1]);
758#endif
759}
760
761/*
762 * report use of invalid credentials
763 */
764void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
765{
766 printk(KERN_ERR "CRED: Invalid credentials\n");
767 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
768 dump_invalid_creds(cred, "Specified", current);
769 BUG();
770}
771EXPORT_SYMBOL(__invalid_creds);
772
773/*
774 * check the credentials on a process
775 */
776void __validate_process_creds(struct task_struct *tsk,
777 const char *file, unsigned line)
778{
779 if (tsk->cred == tsk->real_cred) {
780 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
781 creds_are_invalid(tsk->cred)))
782 goto invalid_creds;
783 } else {
784 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
785 read_cred_subscribers(tsk->cred) < 1 ||
786 creds_are_invalid(tsk->real_cred) ||
787 creds_are_invalid(tsk->cred)))
788 goto invalid_creds;
789 }
790 return;
791
792invalid_creds:
793 printk(KERN_ERR "CRED: Invalid process credentials\n");
794 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
795
796 dump_invalid_creds(tsk->real_cred, "Real", tsk);
797 if (tsk->cred != tsk->real_cred)
798 dump_invalid_creds(tsk->cred, "Effective", tsk);
799 else
800 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
801 BUG();
802}
803EXPORT_SYMBOL(__validate_process_creds);
804
805/*
806 * check creds for do_exit()
807 */
808void validate_creds_for_do_exit(struct task_struct *tsk)
809{
810 kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
811 tsk->real_cred, tsk->cred,
812 atomic_read(&tsk->cred->usage),
813 read_cred_subscribers(tsk->cred));
814
815 __validate_process_creds(tsk, __FILE__, __LINE__);
816}
817
818#endif /* CONFIG_DEBUG_CREDENTIALS */