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Thomas Gleixnerb4d0d232019-05-20 19:08:01 +02001// SPDX-License-Identifier: GPL-2.0-or-later
Kees Cookaf777cd2017-05-13 04:51:40 -07002/* Task credentials management - see Documentation/security/credentials.rst
David Howellsf1752ee2008-11-14 10:39:17 +11003 *
4 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
David Howellsf1752ee2008-11-14 10:39:17 +11006 */
Paul Gortmaker9984de12011-05-23 14:51:41 -04007#include <linux/export.h>
David Howellsf1752ee2008-11-14 10:39:17 +11008#include <linux/cred.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +09009#include <linux/slab.h>
David Howellsf1752ee2008-11-14 10:39:17 +110010#include <linux/sched.h>
Ingo Molnarf7ccbae2017-02-08 18:51:30 +010011#include <linux/sched/coredump.h>
David Howellsf1752ee2008-11-14 10:39:17 +110012#include <linux/key.h>
13#include <linux/keyctl.h>
14#include <linux/init_task.h>
15#include <linux/security.h>
Al Viro40401532012-02-13 03:58:52 +000016#include <linux/binfmts.h>
David Howellsd84f4f92008-11-14 10:39:23 +110017#include <linux/cn_proc.h>
NeilBrownd89b22d2018-12-03 11:30:30 +110018#include <linux/uidgid.h>
David Howellsd84f4f92008-11-14 10:39:23 +110019
David Howellse0e81732009-09-02 09:13:40 +010020#if 0
Joe Perches52aa8532015-09-09 15:36:09 -070021#define kdebug(FMT, ...) \
22 printk("[%-5.5s%5u] " FMT "\n", \
23 current->comm, current->pid, ##__VA_ARGS__)
David Howellse0e81732009-09-02 09:13:40 +010024#else
Joe Perches52aa8532015-09-09 15:36:09 -070025#define kdebug(FMT, ...) \
26do { \
27 if (0) \
28 no_printk("[%-5.5s%5u] " FMT "\n", \
29 current->comm, current->pid, ##__VA_ARGS__); \
30} while (0)
David Howellse0e81732009-09-02 09:13:40 +010031#endif
32
David Howellsd84f4f92008-11-14 10:39:23 +110033static struct kmem_cache *cred_jar;
David Howellsf1752ee2008-11-14 10:39:17 +110034
Iulia Manda28138932015-04-15 16:16:41 -070035/* init to 2 - one for init_task, one to ensure it is never freed */
Rasmus Villemoes32c93972021-05-06 18:02:39 -070036static struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
Iulia Manda28138932015-04-15 16:16:41 -070037
David Howellsf1752ee2008-11-14 10:39:17 +110038/*
39 * The initial credentials for the initial task
40 */
41struct cred init_cred = {
David Howells3b11a1d2008-11-14 10:39:26 +110042 .usage = ATOMIC_INIT(4),
David Howellse0e81732009-09-02 09:13:40 +010043#ifdef CONFIG_DEBUG_CREDENTIALS
44 .subscribers = ATOMIC_INIT(2),
45 .magic = CRED_MAGIC,
46#endif
Eric W. Biederman078de5f2012-02-08 07:00:08 -080047 .uid = GLOBAL_ROOT_UID,
48 .gid = GLOBAL_ROOT_GID,
49 .suid = GLOBAL_ROOT_UID,
50 .sgid = GLOBAL_ROOT_GID,
51 .euid = GLOBAL_ROOT_UID,
52 .egid = GLOBAL_ROOT_GID,
53 .fsuid = GLOBAL_ROOT_UID,
54 .fsgid = GLOBAL_ROOT_GID,
David Howellsf1752ee2008-11-14 10:39:17 +110055 .securebits = SECUREBITS_DEFAULT,
Eric Parisa3232d22011-04-01 17:08:45 -040056 .cap_inheritable = CAP_EMPTY_SET,
David Howellsf1752ee2008-11-14 10:39:17 +110057 .cap_permitted = CAP_FULL_SET,
Eric Parisa3232d22011-04-01 17:08:45 -040058 .cap_effective = CAP_FULL_SET,
59 .cap_bset = CAP_FULL_SET,
David Howellsf1752ee2008-11-14 10:39:17 +110060 .user = INIT_USER,
Serge E. Hallyn47a150e2011-05-13 04:27:54 +010061 .user_ns = &init_user_ns,
David Howellsf1752ee2008-11-14 10:39:17 +110062 .group_info = &init_groups,
Alexey Gladkov905ae012021-04-22 14:27:09 +020063 .ucounts = &init_ucounts,
David Howellsf1752ee2008-11-14 10:39:17 +110064};
65
David Howellse0e81732009-09-02 09:13:40 +010066static inline void set_cred_subscribers(struct cred *cred, int n)
67{
68#ifdef CONFIG_DEBUG_CREDENTIALS
69 atomic_set(&cred->subscribers, n);
70#endif
71}
72
73static inline int read_cred_subscribers(const struct cred *cred)
74{
75#ifdef CONFIG_DEBUG_CREDENTIALS
76 return atomic_read(&cred->subscribers);
77#else
78 return 0;
79#endif
80}
81
82static inline void alter_cred_subscribers(const struct cred *_cred, int n)
83{
84#ifdef CONFIG_DEBUG_CREDENTIALS
85 struct cred *cred = (struct cred *) _cred;
86
87 atomic_add(n, &cred->subscribers);
88#endif
89}
90
David Howellsf1752ee2008-11-14 10:39:17 +110091/*
92 * The RCU callback to actually dispose of a set of credentials
93 */
94static void put_cred_rcu(struct rcu_head *rcu)
95{
96 struct cred *cred = container_of(rcu, struct cred, rcu);
97
David Howellse0e81732009-09-02 09:13:40 +010098 kdebug("put_cred_rcu(%p)", cred);
99
100#ifdef CONFIG_DEBUG_CREDENTIALS
101 if (cred->magic != CRED_MAGIC_DEAD ||
102 atomic_read(&cred->usage) != 0 ||
103 read_cred_subscribers(cred) != 0)
104 panic("CRED: put_cred_rcu() sees %p with"
105 " mag %x, put %p, usage %d, subscr %d\n",
106 cred, cred->magic, cred->put_addr,
107 atomic_read(&cred->usage),
108 read_cred_subscribers(cred));
109#else
David Howellsd84f4f92008-11-14 10:39:23 +1100110 if (atomic_read(&cred->usage) != 0)
111 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
112 cred, atomic_read(&cred->usage));
David Howellse0e81732009-09-02 09:13:40 +0100113#endif
David Howellsf1752ee2008-11-14 10:39:17 +1100114
David Howellsd84f4f92008-11-14 10:39:23 +1100115 security_cred_free(cred);
David Howells3a505972012-10-02 19:24:29 +0100116 key_put(cred->session_keyring);
117 key_put(cred->process_keyring);
David Howellsf1752ee2008-11-14 10:39:17 +1100118 key_put(cred->thread_keyring);
119 key_put(cred->request_key_auth);
David Howells4a5d6ba2009-09-14 12:45:39 +0100120 if (cred->group_info)
121 put_group_info(cred->group_info);
David Howellsf1752ee2008-11-14 10:39:17 +1100122 free_uid(cred->user);
Alexey Gladkov905ae012021-04-22 14:27:09 +0200123 if (cred->ucounts)
124 put_ucounts(cred->ucounts);
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
Linus Torvaldsd7852fb2019-07-11 09:54:40 -0700150 if (cred->non_rcu)
151 put_cred_rcu(&cred->rcu);
152 else
153 call_rcu(&cred->rcu, put_cred_rcu);
David Howellsf1752ee2008-11-14 10:39:17 +1100154}
155EXPORT_SYMBOL(__put_cred);
156
David Howellse0e81732009-09-02 09:13:40 +0100157/*
158 * Clean up a task's credentials when it exits
159 */
160void exit_creds(struct task_struct *tsk)
161{
162 struct cred *cred;
163
164 kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
165 atomic_read(&tsk->cred->usage),
166 read_cred_subscribers(tsk->cred));
167
168 cred = (struct cred *) tsk->real_cred;
169 tsk->real_cred = NULL;
170 validate_creds(cred);
171 alter_cred_subscribers(cred, -1);
172 put_cred(cred);
173
174 cred = (struct cred *) tsk->cred;
175 tsk->cred = NULL;
176 validate_creds(cred);
177 alter_cred_subscribers(cred, -1);
178 put_cred(cred);
David Howells7743c482019-06-19 16:10:15 +0100179
180#ifdef CONFIG_KEYS_REQUEST_CACHE
David Howells8379bb82020-01-14 16:06:14 +0000181 key_put(tsk->cached_requested_key);
182 tsk->cached_requested_key = NULL;
David Howells7743c482019-06-19 16:10:15 +0100183#endif
David Howellsee18d642009-09-02 09:14:21 +0100184}
185
David Howellsde09a972010-07-29 12:45:49 +0100186/**
187 * get_task_cred - Get another task's objective credentials
188 * @task: The task to query
189 *
190 * Get the objective credentials of a task, pinning them so that they can't go
191 * away. Accessing a task's credentials directly is not permitted.
192 *
193 * The caller must also make sure task doesn't get deleted, either by holding a
194 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
195 */
196const struct cred *get_task_cred(struct task_struct *task)
197{
198 const struct cred *cred;
199
200 rcu_read_lock();
201
202 do {
203 cred = __task_cred((task));
204 BUG_ON(!cred);
NeilBrown97d0fb22018-12-03 11:30:30 +1100205 } while (!get_cred_rcu(cred));
David Howellsde09a972010-07-29 12:45:49 +0100206
207 rcu_read_unlock();
208 return cred;
209}
NeilBrowna6d8e762018-12-03 11:30:30 +1100210EXPORT_SYMBOL(get_task_cred);
David Howellsde09a972010-07-29 12:45:49 +0100211
David Howellsee18d642009-09-02 09:14:21 +0100212/*
213 * Allocate blank credentials, such that the credentials can be filled in at a
214 * later date without risk of ENOMEM.
215 */
216struct cred *cred_alloc_blank(void)
217{
218 struct cred *new;
219
220 new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
221 if (!new)
222 return NULL;
223
David Howellsee18d642009-09-02 09:14:21 +0100224 atomic_set(&new->usage, 1);
Tetsuo Handa2edeaa32011-02-07 13:36:10 +0000225#ifdef CONFIG_DEBUG_CREDENTIALS
226 new->magic = CRED_MAGIC;
227#endif
Shakeel Butt84029fd2020-01-04 12:59:43 -0800228 if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
David Howellsee18d642009-09-02 09:14:21 +0100229 goto error;
230
David Howellsee18d642009-09-02 09:14:21 +0100231 return new;
232
233error:
234 abort_creds(new);
235 return NULL;
David Howellse0e81732009-09-02 09:13:40 +0100236}
237
David Howellsd84f4f92008-11-14 10:39:23 +1100238/**
239 * prepare_creds - Prepare a new set of credentials for modification
240 *
241 * Prepare a new set of task credentials for modification. A task's creds
242 * shouldn't generally be modified directly, therefore this function is used to
243 * prepare a new copy, which the caller then modifies and then commits by
244 * calling commit_creds().
245 *
David Howells3b11a1d2008-11-14 10:39:26 +1100246 * Preparation involves making a copy of the objective creds for modification.
247 *
David Howellsd84f4f92008-11-14 10:39:23 +1100248 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
249 *
250 * Call commit_creds() or abort_creds() to clean up.
David Howellsf1752ee2008-11-14 10:39:17 +1100251 */
David Howellsd84f4f92008-11-14 10:39:23 +1100252struct cred *prepare_creds(void)
David Howellsf1752ee2008-11-14 10:39:17 +1100253{
David Howellsd84f4f92008-11-14 10:39:23 +1100254 struct task_struct *task = current;
255 const struct cred *old;
256 struct cred *new;
David Howellsf1752ee2008-11-14 10:39:17 +1100257
David Howellse0e81732009-09-02 09:13:40 +0100258 validate_process_creds();
David Howellsd84f4f92008-11-14 10:39:23 +1100259
260 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
261 if (!new)
262 return NULL;
263
David Howellse0e81732009-09-02 09:13:40 +0100264 kdebug("prepare_creds() alloc %p", new);
265
David Howellsd84f4f92008-11-14 10:39:23 +1100266 old = task->cred;
267 memcpy(new, old, sizeof(struct cred));
268
Linus Torvaldsd7852fb2019-07-11 09:54:40 -0700269 new->non_rcu = 0;
David Howellsd84f4f92008-11-14 10:39:23 +1100270 atomic_set(&new->usage, 1);
David Howellse0e81732009-09-02 09:13:40 +0100271 set_cred_subscribers(new, 0);
David Howellsd84f4f92008-11-14 10:39:23 +1100272 get_group_info(new->group_info);
273 get_uid(new->user);
Eric W. Biederman0093ccb2011-11-16 21:52:53 -0800274 get_user_ns(new->user_ns);
David Howellsf1752ee2008-11-14 10:39:17 +1100275
David Howellsbb952bb2008-11-14 10:39:20 +1100276#ifdef CONFIG_KEYS
David Howells3a505972012-10-02 19:24:29 +0100277 key_get(new->session_keyring);
278 key_get(new->process_keyring);
David Howellsd84f4f92008-11-14 10:39:23 +1100279 key_get(new->thread_keyring);
280 key_get(new->request_key_auth);
David Howellsbb952bb2008-11-14 10:39:20 +1100281#endif
282
David Howellsf1752ee2008-11-14 10:39:17 +1100283#ifdef CONFIG_SECURITY
David Howellsd84f4f92008-11-14 10:39:23 +1100284 new->security = NULL;
David Howellsf1752ee2008-11-14 10:39:17 +1100285#endif
286
Alexey Gladkov905ae012021-04-22 14:27:09 +0200287 new->ucounts = get_ucounts(new->ucounts);
288 if (!new->ucounts)
289 goto error;
290
Alexey Gladkovbbb6d0f2021-08-23 18:16:33 +0200291 if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
292 goto error;
293
David Howellse0e81732009-09-02 09:13:40 +0100294 validate_creds(new);
David Howellsd84f4f92008-11-14 10:39:23 +1100295 return new;
296
297error:
298 abort_creds(new);
299 return NULL;
300}
301EXPORT_SYMBOL(prepare_creds);
302
303/*
David Howellsa6f76f22008-11-14 10:39:24 +1100304 * Prepare credentials for current to perform an execve()
KOSAKI Motohiro9b1bf122010-10-27 15:34:08 -0700305 * - The caller must hold ->cred_guard_mutex
David Howellsa6f76f22008-11-14 10:39:24 +1100306 */
307struct cred *prepare_exec_creds(void)
308{
David Howellsa6f76f22008-11-14 10:39:24 +1100309 struct cred *new;
310
David Howellsa6f76f22008-11-14 10:39:24 +1100311 new = prepare_creds();
David Howells3a505972012-10-02 19:24:29 +0100312 if (!new)
David Howellsa6f76f22008-11-14 10:39:24 +1100313 return new;
David Howellsa6f76f22008-11-14 10:39:24 +1100314
315#ifdef CONFIG_KEYS
316 /* newly exec'd tasks don't get a thread keyring */
317 key_put(new->thread_keyring);
318 new->thread_keyring = NULL;
319
David Howellsa6f76f22008-11-14 10:39:24 +1100320 /* inherit the session keyring; new process keyring */
David Howells3a505972012-10-02 19:24:29 +0100321 key_put(new->process_keyring);
322 new->process_keyring = NULL;
David Howellsa6f76f22008-11-14 10:39:24 +1100323#endif
324
Eric W. Biederman87b047d2020-03-16 12:21:12 -0500325 new->suid = new->fsuid = new->euid;
326 new->sgid = new->fsgid = new->egid;
327
David Howellsa6f76f22008-11-14 10:39:24 +1100328 return new;
329}
330
331/*
David Howellsd84f4f92008-11-14 10:39:23 +1100332 * Copy credentials for the new process created by fork()
333 *
334 * We share if we can, but under some circumstances we have to generate a new
335 * set.
David Howells3b11a1d2008-11-14 10:39:26 +1100336 *
337 * The new process gets the current process's subjective credentials as its
338 * objective and subjective credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100339 */
340int copy_creds(struct task_struct *p, unsigned long clone_flags)
341{
David Howellsd84f4f92008-11-14 10:39:23 +1100342 struct cred *new;
Serge Hallyn18b6e042008-10-15 16:38:45 -0500343 int ret;
David Howellsd84f4f92008-11-14 10:39:23 +1100344
David Howells7743c482019-06-19 16:10:15 +0100345#ifdef CONFIG_KEYS_REQUEST_CACHE
346 p->cached_requested_key = NULL;
347#endif
348
David Howellsd84f4f92008-11-14 10:39:23 +1100349 if (
350#ifdef CONFIG_KEYS
351 !p->cred->thread_keyring &&
352#endif
353 clone_flags & CLONE_THREAD
354 ) {
David Howells3b11a1d2008-11-14 10:39:26 +1100355 p->real_cred = get_cred(p->cred);
David Howellsd84f4f92008-11-14 10:39:23 +1100356 get_cred(p->cred);
David Howellse0e81732009-09-02 09:13:40 +0100357 alter_cred_subscribers(p->cred, 2);
358 kdebug("share_creds(%p{%d,%d})",
359 p->cred, atomic_read(&p->cred->usage),
360 read_cred_subscribers(p->cred));
Alexey Gladkov21d1c5e2021-04-22 14:27:11 +0200361 inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
David Howellsd84f4f92008-11-14 10:39:23 +1100362 return 0;
David Howellsf1752ee2008-11-14 10:39:17 +1100363 }
364
David Howellsd84f4f92008-11-14 10:39:23 +1100365 new = prepare_creds();
366 if (!new)
367 return -ENOMEM;
David Howellsf1752ee2008-11-14 10:39:17 +1100368
Serge Hallyn18b6e042008-10-15 16:38:45 -0500369 if (clone_flags & CLONE_NEWUSER) {
370 ret = create_user_ns(new);
371 if (ret < 0)
372 goto error_put;
Yang Yingliang5e6b8a52021-05-26 22:38:05 +0800373 ret = set_cred_ucounts(new);
374 if (ret < 0)
Alexey Gladkov905ae012021-04-22 14:27:09 +0200375 goto error_put;
Serge Hallyn18b6e042008-10-15 16:38:45 -0500376 }
377
David Howellsd84f4f92008-11-14 10:39:23 +1100378#ifdef CONFIG_KEYS
379 /* new threads get their own thread keyrings if their parent already
380 * had one */
381 if (new->thread_keyring) {
382 key_put(new->thread_keyring);
383 new->thread_keyring = NULL;
384 if (clone_flags & CLONE_THREAD)
385 install_thread_keyring_to_cred(new);
386 }
David Howellsf1752ee2008-11-14 10:39:17 +1100387
David Howells3a505972012-10-02 19:24:29 +0100388 /* The process keyring is only shared between the threads in a process;
389 * anything outside of those threads doesn't inherit.
390 */
David Howellsd84f4f92008-11-14 10:39:23 +1100391 if (!(clone_flags & CLONE_THREAD)) {
David Howells3a505972012-10-02 19:24:29 +0100392 key_put(new->process_keyring);
393 new->process_keyring = NULL;
David Howellsd84f4f92008-11-14 10:39:23 +1100394 }
395#endif
396
David Howells3b11a1d2008-11-14 10:39:26 +1100397 p->cred = p->real_cred = get_cred(new);
Alexey Gladkov21d1c5e2021-04-22 14:27:11 +0200398 inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
David Howellse0e81732009-09-02 09:13:40 +0100399 alter_cred_subscribers(new, 2);
400 validate_creds(new);
David Howellsf1752ee2008-11-14 10:39:17 +1100401 return 0;
Serge Hallyn18b6e042008-10-15 16:38:45 -0500402
403error_put:
404 put_cred(new);
405 return ret;
David Howellsf1752ee2008-11-14 10:39:17 +1100406}
David Howellsd84f4f92008-11-14 10:39:23 +1100407
Eric W. Biedermanaa6d0542012-12-14 08:50:54 -0800408static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
409{
410 const struct user_namespace *set_ns = set->user_ns;
411 const struct user_namespace *subset_ns = subset->user_ns;
412
413 /* If the two credentials are in the same user namespace see if
414 * the capabilities of subset are a subset of set.
415 */
416 if (set_ns == subset_ns)
417 return cap_issubset(subset->cap_permitted, set->cap_permitted);
418
419 /* The credentials are in a different user namespaces
420 * therefore one is a subset of the other only if a set is an
421 * ancestor of subset and set->euid is owner of subset or one
422 * of subsets ancestors.
423 */
424 for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
425 if ((set_ns == subset_ns->parent) &&
426 uid_eq(subset_ns->owner, set->euid))
427 return true;
428 }
429
430 return false;
431}
432
David Howellsd84f4f92008-11-14 10:39:23 +1100433/**
434 * commit_creds - Install new credentials upon the current task
435 * @new: The credentials to be assigned
436 *
437 * Install a new set of credentials to the current task, using RCU to replace
David Howells3b11a1d2008-11-14 10:39:26 +1100438 * the old set. Both the objective and the subjective credentials pointers are
439 * updated. This function may not be called if the subjective credentials are
440 * in an overridden state.
David Howellsd84f4f92008-11-14 10:39:23 +1100441 *
442 * This function eats the caller's reference to the new credentials.
443 *
444 * Always returns 0 thus allowing this function to be tail-called at the end
445 * of, say, sys_setgid().
446 */
447int commit_creds(struct cred *new)
448{
449 struct task_struct *task = current;
David Howellse0e81732009-09-02 09:13:40 +0100450 const struct cred *old = task->real_cred;
David Howellsd84f4f92008-11-14 10:39:23 +1100451
David Howellse0e81732009-09-02 09:13:40 +0100452 kdebug("commit_creds(%p{%d,%d})", new,
453 atomic_read(&new->usage),
454 read_cred_subscribers(new));
455
456 BUG_ON(task->cred != old);
457#ifdef CONFIG_DEBUG_CREDENTIALS
458 BUG_ON(read_cred_subscribers(old) < 2);
459 validate_creds(old);
460 validate_creds(new);
461#endif
David Howellsd84f4f92008-11-14 10:39:23 +1100462 BUG_ON(atomic_read(&new->usage) < 1);
David Howellsd84f4f92008-11-14 10:39:23 +1100463
David Howells3b11a1d2008-11-14 10:39:26 +1100464 get_cred(new); /* we will require a ref for the subj creds too */
465
David Howellsd84f4f92008-11-14 10:39:23 +1100466 /* dumpability changes */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800467 if (!uid_eq(old->euid, new->euid) ||
468 !gid_eq(old->egid, new->egid) ||
469 !uid_eq(old->fsuid, new->fsuid) ||
470 !gid_eq(old->fsgid, new->fsgid) ||
Eric W. Biedermanaa6d0542012-12-14 08:50:54 -0800471 !cred_cap_issubset(old, new)) {
David Howellsb9456372009-01-08 11:18:31 +0000472 if (task->mm)
473 set_dumpable(task->mm, suid_dumpable);
David Howellsd84f4f92008-11-14 10:39:23 +1100474 task->pdeath_signal = 0;
Jann Hornf6581f5b2019-05-29 13:31:57 +0200475 /*
476 * If a task drops privileges and becomes nondumpable,
477 * the dumpability change must become visible before
478 * the credential change; otherwise, a __ptrace_may_access()
479 * racing with this change may be able to attach to a task it
480 * shouldn't be able to attach to (as if the task had dropped
481 * privileges without becoming nondumpable).
482 * Pairs with a read barrier in __ptrace_may_access().
483 */
David Howellsd84f4f92008-11-14 10:39:23 +1100484 smp_wmb();
485 }
486
487 /* alter the thread keyring */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800488 if (!uid_eq(new->fsuid, old->fsuid))
David Howells2e218652019-05-22 14:06:51 +0100489 key_fsuid_changed(new);
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800490 if (!gid_eq(new->fsgid, old->fsgid))
David Howells2e218652019-05-22 14:06:51 +0100491 key_fsgid_changed(new);
David Howellsd84f4f92008-11-14 10:39:23 +1100492
493 /* do it
Vasiliy Kulikov72fa5992011-08-08 19:02:04 +0400494 * RLIMIT_NPROC limits on user->processes have already been checked
495 * in set_user().
David Howellsd84f4f92008-11-14 10:39:23 +1100496 */
David Howellse0e81732009-09-02 09:13:40 +0100497 alter_cred_subscribers(new, 2);
Alexey Gladkov21d1c5e2021-04-22 14:27:11 +0200498 if (new->user != old->user || new->user_ns != old->user_ns)
499 inc_rlimit_ucounts(new->ucounts, UCOUNT_RLIMIT_NPROC, 1);
David Howells3b11a1d2008-11-14 10:39:26 +1100500 rcu_assign_pointer(task->real_cred, new);
David Howellsd84f4f92008-11-14 10:39:23 +1100501 rcu_assign_pointer(task->cred, new);
Eric W. Biederman629715a2021-10-16 12:30:00 -0500502 if (new->user != old->user || new->user_ns != old->user_ns)
Alexey Gladkov21d1c5e2021-04-22 14:27:11 +0200503 dec_rlimit_ucounts(old->ucounts, UCOUNT_RLIMIT_NPROC, 1);
David Howellse0e81732009-09-02 09:13:40 +0100504 alter_cred_subscribers(old, -2);
David Howellsd84f4f92008-11-14 10:39:23 +1100505
David Howellsd84f4f92008-11-14 10:39:23 +1100506 /* send notifications */
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800507 if (!uid_eq(new->uid, old->uid) ||
508 !uid_eq(new->euid, old->euid) ||
509 !uid_eq(new->suid, old->suid) ||
510 !uid_eq(new->fsuid, old->fsuid))
David Howellsd84f4f92008-11-14 10:39:23 +1100511 proc_id_connector(task, PROC_EVENT_UID);
512
Eric W. Biederman078de5f2012-02-08 07:00:08 -0800513 if (!gid_eq(new->gid, old->gid) ||
514 !gid_eq(new->egid, old->egid) ||
515 !gid_eq(new->sgid, old->sgid) ||
516 !gid_eq(new->fsgid, old->fsgid))
David Howellsd84f4f92008-11-14 10:39:23 +1100517 proc_id_connector(task, PROC_EVENT_GID);
518
David Howells3b11a1d2008-11-14 10:39:26 +1100519 /* release the old obj and subj refs both */
520 put_cred(old);
David Howellsd84f4f92008-11-14 10:39:23 +1100521 put_cred(old);
522 return 0;
523}
524EXPORT_SYMBOL(commit_creds);
525
526/**
527 * abort_creds - Discard a set of credentials and unlock the current task
528 * @new: The credentials that were going to be applied
529 *
530 * Discard a set of credentials that were under construction and unlock the
531 * current task.
532 */
533void abort_creds(struct cred *new)
534{
David Howellse0e81732009-09-02 09:13:40 +0100535 kdebug("abort_creds(%p{%d,%d})", new,
536 atomic_read(&new->usage),
537 read_cred_subscribers(new));
538
539#ifdef CONFIG_DEBUG_CREDENTIALS
540 BUG_ON(read_cred_subscribers(new) != 0);
541#endif
David Howellsd84f4f92008-11-14 10:39:23 +1100542 BUG_ON(atomic_read(&new->usage) < 1);
543 put_cred(new);
544}
545EXPORT_SYMBOL(abort_creds);
546
547/**
David Howells3b11a1d2008-11-14 10:39:26 +1100548 * override_creds - Override the current process's subjective credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100549 * @new: The credentials to be assigned
550 *
David Howells3b11a1d2008-11-14 10:39:26 +1100551 * Install a set of temporary override subjective credentials on the current
552 * process, returning the old set for later reversion.
David Howellsd84f4f92008-11-14 10:39:23 +1100553 */
554const struct cred *override_creds(const struct cred *new)
555{
556 const struct cred *old = current->cred;
557
David Howellse0e81732009-09-02 09:13:40 +0100558 kdebug("override_creds(%p{%d,%d})", new,
559 atomic_read(&new->usage),
560 read_cred_subscribers(new));
561
562 validate_creds(old);
563 validate_creds(new);
Linus Torvaldsd7852fb2019-07-11 09:54:40 -0700564
565 /*
566 * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
567 *
568 * That means that we do not clear the 'non_rcu' flag, since
569 * we are only installing the cred into the thread-synchronous
570 * '->cred' pointer, not the '->real_cred' pointer that is
571 * visible to other threads under RCU.
572 *
573 * Also note that we did validate_creds() manually, not depending
574 * on the validation in 'get_cred()'.
575 */
576 get_new_cred((struct cred *)new);
David Howellse0e81732009-09-02 09:13:40 +0100577 alter_cred_subscribers(new, 1);
578 rcu_assign_pointer(current->cred, new);
579 alter_cred_subscribers(old, -1);
580
581 kdebug("override_creds() = %p{%d,%d}", old,
582 atomic_read(&old->usage),
583 read_cred_subscribers(old));
David Howellsd84f4f92008-11-14 10:39:23 +1100584 return old;
585}
586EXPORT_SYMBOL(override_creds);
587
588/**
David Howells3b11a1d2008-11-14 10:39:26 +1100589 * revert_creds - Revert a temporary subjective credentials override
David Howellsd84f4f92008-11-14 10:39:23 +1100590 * @old: The credentials to be restored
591 *
David Howells3b11a1d2008-11-14 10:39:26 +1100592 * Revert a temporary set of override subjective credentials to an old set,
593 * discarding the override set.
David Howellsd84f4f92008-11-14 10:39:23 +1100594 */
595void revert_creds(const struct cred *old)
596{
597 const struct cred *override = current->cred;
598
David Howellse0e81732009-09-02 09:13:40 +0100599 kdebug("revert_creds(%p{%d,%d})", old,
600 atomic_read(&old->usage),
601 read_cred_subscribers(old));
602
603 validate_creds(old);
604 validate_creds(override);
605 alter_cred_subscribers(old, 1);
David Howellsd84f4f92008-11-14 10:39:23 +1100606 rcu_assign_pointer(current->cred, old);
David Howellse0e81732009-09-02 09:13:40 +0100607 alter_cred_subscribers(override, -1);
David Howellsd84f4f92008-11-14 10:39:23 +1100608 put_cred(override);
609}
610EXPORT_SYMBOL(revert_creds);
611
NeilBrownd89b22d2018-12-03 11:30:30 +1100612/**
613 * cred_fscmp - Compare two credentials with respect to filesystem access.
614 * @a: The first credential
615 * @b: The second credential
616 *
617 * cred_cmp() will return zero if both credentials have the same
618 * fsuid, fsgid, and supplementary groups. That is, if they will both
619 * provide the same access to files based on mode/uid/gid.
620 * If the credentials are different, then either -1 or 1 will
621 * be returned depending on whether @a comes before or after @b
622 * respectively in an arbitrary, but stable, ordering of credentials.
623 *
624 * Return: -1, 0, or 1 depending on comparison
625 */
626int cred_fscmp(const struct cred *a, const struct cred *b)
627{
628 struct group_info *ga, *gb;
629 int g;
630
631 if (a == b)
632 return 0;
633 if (uid_lt(a->fsuid, b->fsuid))
634 return -1;
635 if (uid_gt(a->fsuid, b->fsuid))
636 return 1;
637
638 if (gid_lt(a->fsgid, b->fsgid))
639 return -1;
640 if (gid_gt(a->fsgid, b->fsgid))
641 return 1;
642
643 ga = a->group_info;
644 gb = b->group_info;
645 if (ga == gb)
646 return 0;
647 if (ga == NULL)
648 return -1;
649 if (gb == NULL)
650 return 1;
651 if (ga->ngroups < gb->ngroups)
652 return -1;
653 if (ga->ngroups > gb->ngroups)
654 return 1;
655
656 for (g = 0; g < ga->ngroups; g++) {
657 if (gid_lt(ga->gid[g], gb->gid[g]))
658 return -1;
659 if (gid_gt(ga->gid[g], gb->gid[g]))
660 return 1;
661 }
662 return 0;
663}
664EXPORT_SYMBOL(cred_fscmp);
665
Alexey Gladkov905ae012021-04-22 14:27:09 +0200666int set_cred_ucounts(struct cred *new)
667{
Eric W. Biederman34dc2fd2021-10-16 12:47:51 -0500668 struct ucounts *new_ucounts, *old_ucounts = new->ucounts;
Alexey Gladkov905ae012021-04-22 14:27:09 +0200669
Alexey Gladkov905ae012021-04-22 14:27:09 +0200670 /*
671 * This optimization is needed because alloc_ucounts() uses locks
672 * for table lookups.
673 */
Eric W. Biedermana55d0722022-02-09 16:22:20 -0600674 if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->uid))
Alexey Gladkov905ae012021-04-22 14:27:09 +0200675 return 0;
676
Eric W. Biedermana55d0722022-02-09 16:22:20 -0600677 if (!(new_ucounts = alloc_ucounts(new->user_ns, new->uid)))
Alexey Gladkov905ae012021-04-22 14:27:09 +0200678 return -EAGAIN;
679
Eric W. Biederman34dc2fd2021-10-16 12:47:51 -0500680 new->ucounts = new_ucounts;
Eric W. Biederman99c31f92021-10-16 12:51:58 -0500681 put_ucounts(old_ucounts);
Alexey Gladkov905ae012021-04-22 14:27:09 +0200682
683 return 0;
684}
685
David Howellsd84f4f92008-11-14 10:39:23 +1100686/*
687 * initialise the credentials stuff
688 */
689void __init cred_init(void)
690{
691 /* allocate a slab in which we can store credentials */
Vladimir Davydov5d097052016-01-14 15:18:21 -0800692 cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
693 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
David Howellsd84f4f92008-11-14 10:39:23 +1100694}
David Howells3a3b7ce2008-11-14 10:39:28 +1100695
696/**
697 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
698 * @daemon: A userspace daemon to be used as a reference
699 *
700 * Prepare a set of credentials for a kernel service. This can then be used to
701 * override a task's own credentials so that work can be done on behalf of that
702 * task that requires a different subjective context.
703 *
Kees Cook5a17f042022-10-26 16:31:11 -0700704 * @daemon is used to provide a base cred, with the security data derived from
705 * that; if this is "&init_task", they'll be set to 0, no groups, full
706 * capabilities, and no keys.
David Howells3a3b7ce2008-11-14 10:39:28 +1100707 *
708 * The caller may change these controls afterwards if desired.
709 *
710 * Returns the new credentials or NULL if out of memory.
David Howells3a3b7ce2008-11-14 10:39:28 +1100711 */
712struct cred *prepare_kernel_cred(struct task_struct *daemon)
713{
714 const struct cred *old;
715 struct cred *new;
716
Kees Cook5a17f042022-10-26 16:31:11 -0700717 if (WARN_ON_ONCE(!daemon))
718 return NULL;
719
David Howells3a3b7ce2008-11-14 10:39:28 +1100720 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
721 if (!new)
722 return NULL;
723
David Howellse0e81732009-09-02 09:13:40 +0100724 kdebug("prepare_kernel_cred() alloc %p", new);
725
Kees Cook5a17f042022-10-26 16:31:11 -0700726 old = get_task_cred(daemon);
David Howellse0e81732009-09-02 09:13:40 +0100727 validate_creds(old);
728
David Howells43529c92009-01-09 16:13:46 +0000729 *new = *old;
Linus Torvaldsd7852fb2019-07-11 09:54:40 -0700730 new->non_rcu = 0;
Tetsuo Handafb2b2a12011-02-07 13:36:16 +0000731 atomic_set(&new->usage, 1);
732 set_cred_subscribers(new, 0);
David Howells3a3b7ce2008-11-14 10:39:28 +1100733 get_uid(new->user);
Eric W. Biederman0093ccb2011-11-16 21:52:53 -0800734 get_user_ns(new->user_ns);
David Howells3a3b7ce2008-11-14 10:39:28 +1100735 get_group_info(new->group_info);
736
737#ifdef CONFIG_KEYS
David Howells3a505972012-10-02 19:24:29 +0100738 new->session_keyring = NULL;
739 new->process_keyring = NULL;
David Howells3a3b7ce2008-11-14 10:39:28 +1100740 new->thread_keyring = NULL;
David Howells3a505972012-10-02 19:24:29 +0100741 new->request_key_auth = NULL;
David Howells3a3b7ce2008-11-14 10:39:28 +1100742 new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
743#endif
744
745#ifdef CONFIG_SECURITY
746 new->security = NULL;
747#endif
Alexey Gladkov905ae012021-04-22 14:27:09 +0200748 new->ucounts = get_ucounts(new->ucounts);
749 if (!new->ucounts)
750 goto error;
751
Alexey Gladkovbbb6d0f2021-08-23 18:16:33 +0200752 if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
753 goto error;
754
David Howells3a3b7ce2008-11-14 10:39:28 +1100755 put_cred(old);
David Howellse0e81732009-09-02 09:13:40 +0100756 validate_creds(new);
David Howells3a3b7ce2008-11-14 10:39:28 +1100757 return new;
758
759error:
760 put_cred(new);
David Howells0de33682009-01-09 16:13:41 +0000761 put_cred(old);
David Howells3a3b7ce2008-11-14 10:39:28 +1100762 return NULL;
763}
764EXPORT_SYMBOL(prepare_kernel_cred);
765
766/**
767 * set_security_override - Set the security ID in a set of credentials
768 * @new: The credentials to alter
769 * @secid: The LSM security ID to set
770 *
771 * Set the LSM security ID in a set of credentials so that the subjective
772 * security is overridden when an alternative set of credentials is used.
773 */
774int set_security_override(struct cred *new, u32 secid)
775{
776 return security_kernel_act_as(new, secid);
777}
778EXPORT_SYMBOL(set_security_override);
779
780/**
781 * set_security_override_from_ctx - Set the security ID in a set of credentials
782 * @new: The credentials to alter
783 * @secctx: The LSM security context to generate the security ID from.
784 *
785 * Set the LSM security ID in a set of credentials so that the subjective
786 * security is overridden when an alternative set of credentials is used. The
787 * security ID is specified in string form as a security context to be
788 * interpreted by the LSM.
789 */
790int set_security_override_from_ctx(struct cred *new, const char *secctx)
791{
792 u32 secid;
793 int ret;
794
795 ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
796 if (ret < 0)
797 return ret;
798
799 return set_security_override(new, secid);
800}
801EXPORT_SYMBOL(set_security_override_from_ctx);
802
803/**
804 * set_create_files_as - Set the LSM file create context in a set of credentials
805 * @new: The credentials to alter
806 * @inode: The inode to take the context from
807 *
808 * Change the LSM file creation context in a set of credentials to be the same
809 * as the object context of the specified inode, so that the new inodes have
810 * the same MAC context as that inode.
811 */
812int set_create_files_as(struct cred *new, struct inode *inode)
813{
Seth Forshee5f65e5c2016-04-26 14:36:24 -0500814 if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
815 return -EINVAL;
David Howells3a3b7ce2008-11-14 10:39:28 +1100816 new->fsuid = inode->i_uid;
817 new->fsgid = inode->i_gid;
818 return security_kernel_create_files_as(new, inode);
819}
820EXPORT_SYMBOL(set_create_files_as);
David Howellse0e81732009-09-02 09:13:40 +0100821
822#ifdef CONFIG_DEBUG_CREDENTIALS
823
Andrew Morton74908a02009-09-17 17:47:12 -0700824bool creds_are_invalid(const struct cred *cred)
825{
826 if (cred->magic != CRED_MAGIC)
827 return true;
Andrew Morton74908a02009-09-17 17:47:12 -0700828 return false;
829}
Randy Dunlap764db032009-09-18 11:06:47 -0700830EXPORT_SYMBOL(creds_are_invalid);
Andrew Morton74908a02009-09-17 17:47:12 -0700831
David Howellse0e81732009-09-02 09:13:40 +0100832/*
833 * dump invalid credentials
834 */
835static void dump_invalid_creds(const struct cred *cred, const char *label,
836 const struct task_struct *tsk)
837{
838 printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
839 label, cred,
840 cred == &init_cred ? "[init]" : "",
841 cred == tsk->real_cred ? "[real]" : "",
842 cred == tsk->cred ? "[eff]" : "");
843 printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
844 cred->magic, cred->put_addr);
845 printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
846 atomic_read(&cred->usage),
847 read_cred_subscribers(cred));
848 printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
Eric W. Biedermanc9235f42012-04-23 17:06:34 -0700849 from_kuid_munged(&init_user_ns, cred->uid),
850 from_kuid_munged(&init_user_ns, cred->euid),
851 from_kuid_munged(&init_user_ns, cred->suid),
852 from_kuid_munged(&init_user_ns, cred->fsuid));
David Howellse0e81732009-09-02 09:13:40 +0100853 printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
Eric W. Biedermanc9235f42012-04-23 17:06:34 -0700854 from_kgid_munged(&init_user_ns, cred->gid),
855 from_kgid_munged(&init_user_ns, cred->egid),
856 from_kgid_munged(&init_user_ns, cred->sgid),
857 from_kgid_munged(&init_user_ns, cred->fsgid));
David Howellse0e81732009-09-02 09:13:40 +0100858#ifdef CONFIG_SECURITY
859 printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
860 if ((unsigned long) cred->security >= PAGE_SIZE &&
861 (((unsigned long) cred->security & 0xffffff00) !=
862 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
863 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
864 ((u32*)cred->security)[0],
865 ((u32*)cred->security)[1]);
866#endif
867}
868
869/*
870 * report use of invalid credentials
871 */
Peter Zijlstra105cd682022-03-14 17:58:35 +0100872void __noreturn __invalid_creds(const struct cred *cred, const char *file, unsigned line)
David Howellse0e81732009-09-02 09:13:40 +0100873{
874 printk(KERN_ERR "CRED: Invalid credentials\n");
875 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
876 dump_invalid_creds(cred, "Specified", current);
877 BUG();
878}
879EXPORT_SYMBOL(__invalid_creds);
880
881/*
882 * check the credentials on a process
883 */
884void __validate_process_creds(struct task_struct *tsk,
885 const char *file, unsigned line)
886{
887 if (tsk->cred == tsk->real_cred) {
888 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
889 creds_are_invalid(tsk->cred)))
890 goto invalid_creds;
891 } else {
892 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
893 read_cred_subscribers(tsk->cred) < 1 ||
894 creds_are_invalid(tsk->real_cred) ||
895 creds_are_invalid(tsk->cred)))
896 goto invalid_creds;
897 }
898 return;
899
900invalid_creds:
901 printk(KERN_ERR "CRED: Invalid process credentials\n");
902 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
903
904 dump_invalid_creds(tsk->real_cred, "Real", tsk);
905 if (tsk->cred != tsk->real_cred)
906 dump_invalid_creds(tsk->cred, "Effective", tsk);
907 else
908 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
909 BUG();
910}
911EXPORT_SYMBOL(__validate_process_creds);
912
913/*
914 * check creds for do_exit()
915 */
916void validate_creds_for_do_exit(struct task_struct *tsk)
917{
918 kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
919 tsk->real_cred, tsk->cred,
920 atomic_read(&tsk->cred->usage),
921 read_cred_subscribers(tsk->cred));
922
923 __validate_process_creds(tsk, __FILE__, __LINE__);
924}
925
926#endif /* CONFIG_DEBUG_CREDENTIALS */