Commit | Line | Data |
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b4d0d230 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
af777cd1 | 2 | /* Task credentials management - see Documentation/security/credentials.rst |
f1752eec DH |
3 | * |
4 | * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. | |
5 | * Written by David Howells (dhowells@redhat.com) | |
f1752eec | 6 | */ |
4099451a | 7 | |
8 | #define pr_fmt(fmt) "CRED: " fmt | |
9 | ||
9984de1a | 10 | #include <linux/export.h> |
f1752eec | 11 | #include <linux/cred.h> |
5a0e3ad6 | 12 | #include <linux/slab.h> |
f1752eec | 13 | #include <linux/sched.h> |
f7ccbae4 | 14 | #include <linux/sched/coredump.h> |
f1752eec DH |
15 | #include <linux/key.h> |
16 | #include <linux/keyctl.h> | |
17 | #include <linux/init_task.h> | |
18 | #include <linux/security.h> | |
40401530 | 19 | #include <linux/binfmts.h> |
d84f4f99 | 20 | #include <linux/cn_proc.h> |
d89b22d4 | 21 | #include <linux/uidgid.h> |
d84f4f99 | 22 | |
e0e81739 | 23 | #if 0 |
52aa8536 JP |
24 | #define kdebug(FMT, ...) \ |
25 | printk("[%-5.5s%5u] " FMT "\n", \ | |
26 | current->comm, current->pid, ##__VA_ARGS__) | |
e0e81739 | 27 | #else |
52aa8536 JP |
28 | #define kdebug(FMT, ...) \ |
29 | do { \ | |
30 | if (0) \ | |
31 | no_printk("[%-5.5s%5u] " FMT "\n", \ | |
32 | current->comm, current->pid, ##__VA_ARGS__); \ | |
33 | } while (0) | |
e0e81739 DH |
34 | #endif |
35 | ||
d84f4f99 | 36 | static struct kmem_cache *cred_jar; |
f1752eec | 37 | |
2813893f | 38 | /* init to 2 - one for init_task, one to ensure it is never freed */ |
d7700842 | 39 | static struct group_info init_groups = { .usage = REFCOUNT_INIT(2) }; |
2813893f | 40 | |
f1752eec DH |
41 | /* |
42 | * The initial credentials for the initial task | |
43 | */ | |
44 | struct cred init_cred = { | |
3b11a1de | 45 | .usage = ATOMIC_INIT(4), |
e0e81739 DH |
46 | #ifdef CONFIG_DEBUG_CREDENTIALS |
47 | .subscribers = ATOMIC_INIT(2), | |
48 | .magic = CRED_MAGIC, | |
49 | #endif | |
078de5f7 EB |
50 | .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, | |
f1752eec | 58 | .securebits = SECUREBITS_DEFAULT, |
a3232d2f | 59 | .cap_inheritable = CAP_EMPTY_SET, |
f1752eec | 60 | .cap_permitted = CAP_FULL_SET, |
a3232d2f EP |
61 | .cap_effective = CAP_FULL_SET, |
62 | .cap_bset = CAP_FULL_SET, | |
f1752eec | 63 | .user = INIT_USER, |
47a150ed | 64 | .user_ns = &init_user_ns, |
f1752eec | 65 | .group_info = &init_groups, |
905ae01c | 66 | .ucounts = &init_ucounts, |
f1752eec DH |
67 | }; |
68 | ||
e0e81739 DH |
69 | static inline void set_cred_subscribers(struct cred *cred, int n) |
70 | { | |
71 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
72 | atomic_set(&cred->subscribers, n); | |
73 | #endif | |
74 | } | |
75 | ||
76 | static inline int read_cred_subscribers(const struct cred *cred) | |
77 | { | |
78 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
79 | return atomic_read(&cred->subscribers); | |
80 | #else | |
81 | return 0; | |
82 | #endif | |
83 | } | |
84 | ||
85 | static inline void alter_cred_subscribers(const struct cred *_cred, int n) | |
86 | { | |
87 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
88 | struct cred *cred = (struct cred *) _cred; | |
89 | ||
90 | atomic_add(n, &cred->subscribers); | |
91 | #endif | |
92 | } | |
93 | ||
f1752eec DH |
94 | /* |
95 | * The RCU callback to actually dispose of a set of credentials | |
96 | */ | |
97 | static void put_cred_rcu(struct rcu_head *rcu) | |
98 | { | |
99 | struct cred *cred = container_of(rcu, struct cred, rcu); | |
100 | ||
e0e81739 DH |
101 | kdebug("put_cred_rcu(%p)", cred); |
102 | ||
103 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
104 | if (cred->magic != CRED_MAGIC_DEAD || | |
105 | atomic_read(&cred->usage) != 0 || | |
106 | read_cred_subscribers(cred) != 0) | |
107 | panic("CRED: put_cred_rcu() sees %p with" | |
108 | " mag %x, put %p, usage %d, subscr %d\n", | |
109 | cred, cred->magic, cred->put_addr, | |
110 | atomic_read(&cred->usage), | |
111 | read_cred_subscribers(cred)); | |
112 | #else | |
d84f4f99 DH |
113 | if (atomic_read(&cred->usage) != 0) |
114 | panic("CRED: put_cred_rcu() sees %p with usage %d\n", | |
115 | cred, atomic_read(&cred->usage)); | |
e0e81739 | 116 | #endif |
f1752eec | 117 | |
d84f4f99 | 118 | security_cred_free(cred); |
3a50597d DH |
119 | key_put(cred->session_keyring); |
120 | key_put(cred->process_keyring); | |
f1752eec DH |
121 | key_put(cred->thread_keyring); |
122 | key_put(cred->request_key_auth); | |
4a5d6ba1 DH |
123 | if (cred->group_info) |
124 | put_group_info(cred->group_info); | |
f1752eec | 125 | free_uid(cred->user); |
905ae01c AG |
126 | if (cred->ucounts) |
127 | put_ucounts(cred->ucounts); | |
0093ccb6 | 128 | put_user_ns(cred->user_ns); |
d84f4f99 | 129 | kmem_cache_free(cred_jar, cred); |
f1752eec DH |
130 | } |
131 | ||
132 | /** | |
133 | * __put_cred - Destroy a set of credentials | |
d84f4f99 | 134 | * @cred: The record to release |
f1752eec DH |
135 | * |
136 | * Destroy a set of credentials on which no references remain. | |
137 | */ | |
138 | void __put_cred(struct cred *cred) | |
139 | { | |
e0e81739 DH |
140 | kdebug("__put_cred(%p{%d,%d})", cred, |
141 | atomic_read(&cred->usage), | |
142 | read_cred_subscribers(cred)); | |
143 | ||
d84f4f99 | 144 | BUG_ON(atomic_read(&cred->usage) != 0); |
e0e81739 DH |
145 | #ifdef CONFIG_DEBUG_CREDENTIALS |
146 | BUG_ON(read_cred_subscribers(cred) != 0); | |
147 | cred->magic = CRED_MAGIC_DEAD; | |
148 | cred->put_addr = __builtin_return_address(0); | |
149 | #endif | |
150 | BUG_ON(cred == current->cred); | |
151 | BUG_ON(cred == current->real_cred); | |
d84f4f99 | 152 | |
d7852fbd LT |
153 | if (cred->non_rcu) |
154 | put_cred_rcu(&cred->rcu); | |
155 | else | |
156 | call_rcu(&cred->rcu, put_cred_rcu); | |
f1752eec DH |
157 | } |
158 | EXPORT_SYMBOL(__put_cred); | |
159 | ||
e0e81739 DH |
160 | /* |
161 | * Clean up a task's credentials when it exits | |
162 | */ | |
163 | void exit_creds(struct task_struct *tsk) | |
164 | { | |
41e84562 | 165 | struct cred *real_cred, *cred; |
e0e81739 DH |
166 | |
167 | kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred, | |
168 | atomic_read(&tsk->cred->usage), | |
169 | read_cred_subscribers(tsk->cred)); | |
170 | ||
41e84562 | 171 | real_cred = (struct cred *) tsk->real_cred; |
e0e81739 | 172 | tsk->real_cred = NULL; |
e0e81739 DH |
173 | |
174 | cred = (struct cred *) tsk->cred; | |
175 | tsk->cred = NULL; | |
41e84562 | 176 | |
e0e81739 | 177 | validate_creds(cred); |
41e84562 MG |
178 | if (real_cred == cred) { |
179 | alter_cred_subscribers(cred, -2); | |
180 | put_cred_many(cred, 2); | |
181 | } else { | |
182 | validate_creds(real_cred); | |
183 | alter_cred_subscribers(real_cred, -1); | |
184 | put_cred(real_cred); | |
185 | alter_cred_subscribers(cred, -1); | |
186 | put_cred(cred); | |
187 | } | |
7743c48e DH |
188 | |
189 | #ifdef CONFIG_KEYS_REQUEST_CACHE | |
8379bb84 DH |
190 | key_put(tsk->cached_requested_key); |
191 | tsk->cached_requested_key = NULL; | |
7743c48e | 192 | #endif |
ee18d64c DH |
193 | } |
194 | ||
de09a977 DH |
195 | /** |
196 | * get_task_cred - Get another task's objective credentials | |
197 | * @task: The task to query | |
198 | * | |
199 | * Get the objective credentials of a task, pinning them so that they can't go | |
200 | * away. Accessing a task's credentials directly is not permitted. | |
201 | * | |
202 | * The caller must also make sure task doesn't get deleted, either by holding a | |
203 | * ref on task or by holding tasklist_lock to prevent it from being unlinked. | |
204 | */ | |
205 | const struct cred *get_task_cred(struct task_struct *task) | |
206 | { | |
207 | const struct cred *cred; | |
208 | ||
209 | rcu_read_lock(); | |
210 | ||
211 | do { | |
212 | cred = __task_cred((task)); | |
213 | BUG_ON(!cred); | |
97d0fb23 | 214 | } while (!get_cred_rcu(cred)); |
de09a977 DH |
215 | |
216 | rcu_read_unlock(); | |
217 | return cred; | |
218 | } | |
a6d8e763 | 219 | EXPORT_SYMBOL(get_task_cred); |
de09a977 | 220 | |
ee18d64c DH |
221 | /* |
222 | * Allocate blank credentials, such that the credentials can be filled in at a | |
223 | * later date without risk of ENOMEM. | |
224 | */ | |
225 | struct cred *cred_alloc_blank(void) | |
226 | { | |
227 | struct cred *new; | |
228 | ||
229 | new = kmem_cache_zalloc(cred_jar, GFP_KERNEL); | |
230 | if (!new) | |
231 | return NULL; | |
232 | ||
ee18d64c | 233 | atomic_set(&new->usage, 1); |
2edeaa34 TH |
234 | #ifdef CONFIG_DEBUG_CREDENTIALS |
235 | new->magic = CRED_MAGIC; | |
236 | #endif | |
84029fd0 | 237 | if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0) |
ee18d64c DH |
238 | goto error; |
239 | ||
ee18d64c DH |
240 | return new; |
241 | ||
242 | error: | |
243 | abort_creds(new); | |
244 | return NULL; | |
e0e81739 DH |
245 | } |
246 | ||
d84f4f99 DH |
247 | /** |
248 | * prepare_creds - Prepare a new set of credentials for modification | |
249 | * | |
250 | * Prepare a new set of task credentials for modification. A task's creds | |
251 | * shouldn't generally be modified directly, therefore this function is used to | |
252 | * prepare a new copy, which the caller then modifies and then commits by | |
253 | * calling commit_creds(). | |
254 | * | |
3b11a1de DH |
255 | * Preparation involves making a copy of the objective creds for modification. |
256 | * | |
d84f4f99 DH |
257 | * Returns a pointer to the new creds-to-be if successful, NULL otherwise. |
258 | * | |
259 | * Call commit_creds() or abort_creds() to clean up. | |
260 | */ | |
261 | struct cred *prepare_creds(void) | |
262 | { | |
263 | struct task_struct *task = current; | |
264 | const struct cred *old; | |
265 | struct cred *new; | |
266 | ||
e0e81739 | 267 | validate_process_creds(); |
d84f4f99 DH |
268 | |
269 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); | |
270 | if (!new) | |
271 | return NULL; | |
272 | ||
e0e81739 DH |
273 | kdebug("prepare_creds() alloc %p", new); |
274 | ||
d84f4f99 DH |
275 | old = task->cred; |
276 | memcpy(new, old, sizeof(struct cred)); | |
277 | ||
d7852fbd | 278 | new->non_rcu = 0; |
d84f4f99 | 279 | atomic_set(&new->usage, 1); |
e0e81739 | 280 | set_cred_subscribers(new, 0); |
d84f4f99 DH |
281 | get_group_info(new->group_info); |
282 | get_uid(new->user); | |
0093ccb6 | 283 | get_user_ns(new->user_ns); |
d84f4f99 DH |
284 | |
285 | #ifdef CONFIG_KEYS | |
3a50597d DH |
286 | key_get(new->session_keyring); |
287 | key_get(new->process_keyring); | |
d84f4f99 DH |
288 | key_get(new->thread_keyring); |
289 | key_get(new->request_key_auth); | |
d84f4f99 DH |
290 | #endif |
291 | ||
292 | #ifdef CONFIG_SECURITY | |
293 | new->security = NULL; | |
294 | #endif | |
295 | ||
905ae01c AG |
296 | new->ucounts = get_ucounts(new->ucounts); |
297 | if (!new->ucounts) | |
298 | goto error; | |
299 | ||
bbb6d0f3 AG |
300 | if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) |
301 | goto error; | |
302 | ||
e0e81739 | 303 | validate_creds(new); |
d84f4f99 DH |
304 | return new; |
305 | ||
306 | error: | |
307 | abort_creds(new); | |
308 | return NULL; | |
309 | } | |
310 | EXPORT_SYMBOL(prepare_creds); | |
311 | ||
a6f76f23 DH |
312 | /* |
313 | * Prepare credentials for current to perform an execve() | |
9b1bf12d | 314 | * - The caller must hold ->cred_guard_mutex |
a6f76f23 DH |
315 | */ |
316 | struct cred *prepare_exec_creds(void) | |
317 | { | |
a6f76f23 DH |
318 | struct cred *new; |
319 | ||
a6f76f23 | 320 | new = prepare_creds(); |
3a50597d | 321 | if (!new) |
a6f76f23 | 322 | return new; |
a6f76f23 DH |
323 | |
324 | #ifdef CONFIG_KEYS | |
325 | /* newly exec'd tasks don't get a thread keyring */ | |
326 | key_put(new->thread_keyring); | |
327 | new->thread_keyring = NULL; | |
328 | ||
a6f76f23 | 329 | /* inherit the session keyring; new process keyring */ |
3a50597d DH |
330 | key_put(new->process_keyring); |
331 | new->process_keyring = NULL; | |
a6f76f23 DH |
332 | #endif |
333 | ||
87b047d2 EB |
334 | new->suid = new->fsuid = new->euid; |
335 | new->sgid = new->fsgid = new->egid; | |
336 | ||
a6f76f23 DH |
337 | return new; |
338 | } | |
339 | ||
f1752eec DH |
340 | /* |
341 | * Copy credentials for the new process created by fork() | |
d84f4f99 DH |
342 | * |
343 | * We share if we can, but under some circumstances we have to generate a new | |
344 | * set. | |
3b11a1de DH |
345 | * |
346 | * The new process gets the current process's subjective credentials as its | |
347 | * objective and subjective credentials | |
f1752eec DH |
348 | */ |
349 | int copy_creds(struct task_struct *p, unsigned long clone_flags) | |
350 | { | |
d84f4f99 | 351 | struct cred *new; |
18b6e041 | 352 | int ret; |
d84f4f99 | 353 | |
7743c48e DH |
354 | #ifdef CONFIG_KEYS_REQUEST_CACHE |
355 | p->cached_requested_key = NULL; | |
356 | #endif | |
357 | ||
d84f4f99 DH |
358 | if ( |
359 | #ifdef CONFIG_KEYS | |
360 | !p->cred->thread_keyring && | |
361 | #endif | |
362 | clone_flags & CLONE_THREAD | |
363 | ) { | |
41e84562 | 364 | p->real_cred = get_cred_many(p->cred, 2); |
e0e81739 DH |
365 | alter_cred_subscribers(p->cred, 2); |
366 | kdebug("share_creds(%p{%d,%d})", | |
367 | p->cred, atomic_read(&p->cred->usage), | |
368 | read_cred_subscribers(p->cred)); | |
21d1c5e3 | 369 | inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); |
d84f4f99 DH |
370 | return 0; |
371 | } | |
372 | ||
373 | new = prepare_creds(); | |
374 | if (!new) | |
f1752eec DH |
375 | return -ENOMEM; |
376 | ||
18b6e041 SH |
377 | if (clone_flags & CLONE_NEWUSER) { |
378 | ret = create_user_ns(new); | |
379 | if (ret < 0) | |
380 | goto error_put; | |
5e6b8a50 YY |
381 | ret = set_cred_ucounts(new); |
382 | if (ret < 0) | |
905ae01c | 383 | goto error_put; |
18b6e041 SH |
384 | } |
385 | ||
bb952bb9 | 386 | #ifdef CONFIG_KEYS |
d84f4f99 DH |
387 | /* new threads get their own thread keyrings if their parent already |
388 | * had one */ | |
389 | if (new->thread_keyring) { | |
390 | key_put(new->thread_keyring); | |
391 | new->thread_keyring = NULL; | |
392 | if (clone_flags & CLONE_THREAD) | |
393 | install_thread_keyring_to_cred(new); | |
394 | } | |
395 | ||
3a50597d DH |
396 | /* The process keyring is only shared between the threads in a process; |
397 | * anything outside of those threads doesn't inherit. | |
398 | */ | |
d84f4f99 | 399 | if (!(clone_flags & CLONE_THREAD)) { |
3a50597d DH |
400 | key_put(new->process_keyring); |
401 | new->process_keyring = NULL; | |
bb952bb9 DH |
402 | } |
403 | #endif | |
404 | ||
3b11a1de | 405 | p->cred = p->real_cred = get_cred(new); |
21d1c5e3 | 406 | inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); |
e0e81739 DH |
407 | alter_cred_subscribers(new, 2); |
408 | validate_creds(new); | |
d84f4f99 | 409 | return 0; |
18b6e041 SH |
410 | |
411 | error_put: | |
412 | put_cred(new); | |
413 | return ret; | |
d84f4f99 | 414 | } |
f1752eec | 415 | |
aa6d054e EB |
416 | static bool cred_cap_issubset(const struct cred *set, const struct cred *subset) |
417 | { | |
418 | const struct user_namespace *set_ns = set->user_ns; | |
419 | const struct user_namespace *subset_ns = subset->user_ns; | |
420 | ||
421 | /* If the two credentials are in the same user namespace see if | |
422 | * the capabilities of subset are a subset of set. | |
423 | */ | |
424 | if (set_ns == subset_ns) | |
425 | return cap_issubset(subset->cap_permitted, set->cap_permitted); | |
426 | ||
427 | /* The credentials are in a different user namespaces | |
428 | * therefore one is a subset of the other only if a set is an | |
429 | * ancestor of subset and set->euid is owner of subset or one | |
430 | * of subsets ancestors. | |
431 | */ | |
432 | for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) { | |
433 | if ((set_ns == subset_ns->parent) && | |
434 | uid_eq(subset_ns->owner, set->euid)) | |
435 | return true; | |
436 | } | |
437 | ||
438 | return false; | |
439 | } | |
440 | ||
d84f4f99 DH |
441 | /** |
442 | * commit_creds - Install new credentials upon the current task | |
443 | * @new: The credentials to be assigned | |
444 | * | |
445 | * Install a new set of credentials to the current task, using RCU to replace | |
3b11a1de DH |
446 | * the old set. Both the objective and the subjective credentials pointers are |
447 | * updated. This function may not be called if the subjective credentials are | |
448 | * in an overridden state. | |
d84f4f99 DH |
449 | * |
450 | * This function eats the caller's reference to the new credentials. | |
451 | * | |
452 | * Always returns 0 thus allowing this function to be tail-called at the end | |
453 | * of, say, sys_setgid(). | |
454 | */ | |
455 | int commit_creds(struct cred *new) | |
456 | { | |
457 | struct task_struct *task = current; | |
e0e81739 | 458 | const struct cred *old = task->real_cred; |
d84f4f99 | 459 | |
e0e81739 DH |
460 | kdebug("commit_creds(%p{%d,%d})", new, |
461 | atomic_read(&new->usage), | |
462 | read_cred_subscribers(new)); | |
463 | ||
464 | BUG_ON(task->cred != old); | |
465 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
466 | BUG_ON(read_cred_subscribers(old) < 2); | |
467 | validate_creds(old); | |
468 | validate_creds(new); | |
469 | #endif | |
d84f4f99 | 470 | BUG_ON(atomic_read(&new->usage) < 1); |
d84f4f99 | 471 | |
3b11a1de DH |
472 | get_cred(new); /* we will require a ref for the subj creds too */ |
473 | ||
d84f4f99 | 474 | /* dumpability changes */ |
078de5f7 EB |
475 | if (!uid_eq(old->euid, new->euid) || |
476 | !gid_eq(old->egid, new->egid) || | |
477 | !uid_eq(old->fsuid, new->fsuid) || | |
478 | !gid_eq(old->fsgid, new->fsgid) || | |
aa6d054e | 479 | !cred_cap_issubset(old, new)) { |
b9456371 DH |
480 | if (task->mm) |
481 | set_dumpable(task->mm, suid_dumpable); | |
d84f4f99 | 482 | task->pdeath_signal = 0; |
f6581f5b JH |
483 | /* |
484 | * If a task drops privileges and becomes nondumpable, | |
485 | * the dumpability change must become visible before | |
486 | * the credential change; otherwise, a __ptrace_may_access() | |
487 | * racing with this change may be able to attach to a task it | |
488 | * shouldn't be able to attach to (as if the task had dropped | |
489 | * privileges without becoming nondumpable). | |
490 | * Pairs with a read barrier in __ptrace_may_access(). | |
491 | */ | |
d84f4f99 | 492 | smp_wmb(); |
f1752eec DH |
493 | } |
494 | ||
d84f4f99 | 495 | /* alter the thread keyring */ |
078de5f7 | 496 | if (!uid_eq(new->fsuid, old->fsuid)) |
2e21865f | 497 | key_fsuid_changed(new); |
078de5f7 | 498 | if (!gid_eq(new->fsgid, old->fsgid)) |
2e21865f | 499 | key_fsgid_changed(new); |
d84f4f99 DH |
500 | |
501 | /* do it | |
72fa5997 VK |
502 | * RLIMIT_NPROC limits on user->processes have already been checked |
503 | * in set_user(). | |
d84f4f99 | 504 | */ |
e0e81739 | 505 | alter_cred_subscribers(new, 2); |
21d1c5e3 AG |
506 | if (new->user != old->user || new->user_ns != old->user_ns) |
507 | inc_rlimit_ucounts(new->ucounts, UCOUNT_RLIMIT_NPROC, 1); | |
3b11a1de | 508 | rcu_assign_pointer(task->real_cred, new); |
d84f4f99 | 509 | rcu_assign_pointer(task->cred, new); |
629715ad | 510 | if (new->user != old->user || new->user_ns != old->user_ns) |
21d1c5e3 | 511 | dec_rlimit_ucounts(old->ucounts, UCOUNT_RLIMIT_NPROC, 1); |
e0e81739 | 512 | alter_cred_subscribers(old, -2); |
d84f4f99 | 513 | |
d84f4f99 | 514 | /* send notifications */ |
078de5f7 EB |
515 | if (!uid_eq(new->uid, old->uid) || |
516 | !uid_eq(new->euid, old->euid) || | |
517 | !uid_eq(new->suid, old->suid) || | |
518 | !uid_eq(new->fsuid, old->fsuid)) | |
d84f4f99 | 519 | proc_id_connector(task, PROC_EVENT_UID); |
f1752eec | 520 | |
078de5f7 EB |
521 | if (!gid_eq(new->gid, old->gid) || |
522 | !gid_eq(new->egid, old->egid) || | |
523 | !gid_eq(new->sgid, old->sgid) || | |
524 | !gid_eq(new->fsgid, old->fsgid)) | |
d84f4f99 | 525 | proc_id_connector(task, PROC_EVENT_GID); |
f1752eec | 526 | |
3b11a1de | 527 | /* release the old obj and subj refs both */ |
41e84562 | 528 | put_cred_many(old, 2); |
f1752eec DH |
529 | return 0; |
530 | } | |
d84f4f99 DH |
531 | EXPORT_SYMBOL(commit_creds); |
532 | ||
533 | /** | |
534 | * abort_creds - Discard a set of credentials and unlock the current task | |
535 | * @new: The credentials that were going to be applied | |
536 | * | |
537 | * Discard a set of credentials that were under construction and unlock the | |
538 | * current task. | |
539 | */ | |
540 | void abort_creds(struct cred *new) | |
541 | { | |
e0e81739 DH |
542 | kdebug("abort_creds(%p{%d,%d})", new, |
543 | atomic_read(&new->usage), | |
544 | read_cred_subscribers(new)); | |
545 | ||
546 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
547 | BUG_ON(read_cred_subscribers(new) != 0); | |
548 | #endif | |
d84f4f99 DH |
549 | BUG_ON(atomic_read(&new->usage) < 1); |
550 | put_cred(new); | |
551 | } | |
552 | EXPORT_SYMBOL(abort_creds); | |
553 | ||
554 | /** | |
3b11a1de | 555 | * override_creds - Override the current process's subjective credentials |
d84f4f99 DH |
556 | * @new: The credentials to be assigned |
557 | * | |
3b11a1de DH |
558 | * Install a set of temporary override subjective credentials on the current |
559 | * process, returning the old set for later reversion. | |
d84f4f99 DH |
560 | */ |
561 | const struct cred *override_creds(const struct cred *new) | |
562 | { | |
563 | const struct cred *old = current->cred; | |
564 | ||
e0e81739 DH |
565 | kdebug("override_creds(%p{%d,%d})", new, |
566 | atomic_read(&new->usage), | |
567 | read_cred_subscribers(new)); | |
568 | ||
569 | validate_creds(old); | |
570 | validate_creds(new); | |
d7852fbd LT |
571 | |
572 | /* | |
573 | * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'. | |
574 | * | |
575 | * That means that we do not clear the 'non_rcu' flag, since | |
576 | * we are only installing the cred into the thread-synchronous | |
577 | * '->cred' pointer, not the '->real_cred' pointer that is | |
578 | * visible to other threads under RCU. | |
579 | * | |
580 | * Also note that we did validate_creds() manually, not depending | |
581 | * on the validation in 'get_cred()'. | |
582 | */ | |
583 | get_new_cred((struct cred *)new); | |
e0e81739 DH |
584 | alter_cred_subscribers(new, 1); |
585 | rcu_assign_pointer(current->cred, new); | |
586 | alter_cred_subscribers(old, -1); | |
587 | ||
588 | kdebug("override_creds() = %p{%d,%d}", old, | |
589 | atomic_read(&old->usage), | |
590 | read_cred_subscribers(old)); | |
d84f4f99 DH |
591 | return old; |
592 | } | |
593 | EXPORT_SYMBOL(override_creds); | |
594 | ||
595 | /** | |
3b11a1de | 596 | * revert_creds - Revert a temporary subjective credentials override |
d84f4f99 DH |
597 | * @old: The credentials to be restored |
598 | * | |
3b11a1de DH |
599 | * Revert a temporary set of override subjective credentials to an old set, |
600 | * discarding the override set. | |
d84f4f99 DH |
601 | */ |
602 | void revert_creds(const struct cred *old) | |
603 | { | |
604 | const struct cred *override = current->cred; | |
605 | ||
e0e81739 DH |
606 | kdebug("revert_creds(%p{%d,%d})", old, |
607 | atomic_read(&old->usage), | |
608 | read_cred_subscribers(old)); | |
609 | ||
610 | validate_creds(old); | |
611 | validate_creds(override); | |
612 | alter_cred_subscribers(old, 1); | |
d84f4f99 | 613 | rcu_assign_pointer(current->cred, old); |
e0e81739 | 614 | alter_cred_subscribers(override, -1); |
d84f4f99 DH |
615 | put_cred(override); |
616 | } | |
617 | EXPORT_SYMBOL(revert_creds); | |
618 | ||
d89b22d4 N |
619 | /** |
620 | * cred_fscmp - Compare two credentials with respect to filesystem access. | |
621 | * @a: The first credential | |
622 | * @b: The second credential | |
623 | * | |
624 | * cred_cmp() will return zero if both credentials have the same | |
625 | * fsuid, fsgid, and supplementary groups. That is, if they will both | |
626 | * provide the same access to files based on mode/uid/gid. | |
627 | * If the credentials are different, then either -1 or 1 will | |
628 | * be returned depending on whether @a comes before or after @b | |
629 | * respectively in an arbitrary, but stable, ordering of credentials. | |
630 | * | |
631 | * Return: -1, 0, or 1 depending on comparison | |
632 | */ | |
633 | int cred_fscmp(const struct cred *a, const struct cred *b) | |
634 | { | |
635 | struct group_info *ga, *gb; | |
636 | int g; | |
637 | ||
638 | if (a == b) | |
639 | return 0; | |
640 | if (uid_lt(a->fsuid, b->fsuid)) | |
641 | return -1; | |
642 | if (uid_gt(a->fsuid, b->fsuid)) | |
643 | return 1; | |
644 | ||
645 | if (gid_lt(a->fsgid, b->fsgid)) | |
646 | return -1; | |
647 | if (gid_gt(a->fsgid, b->fsgid)) | |
648 | return 1; | |
649 | ||
650 | ga = a->group_info; | |
651 | gb = b->group_info; | |
652 | if (ga == gb) | |
653 | return 0; | |
654 | if (ga == NULL) | |
655 | return -1; | |
656 | if (gb == NULL) | |
657 | return 1; | |
658 | if (ga->ngroups < gb->ngroups) | |
659 | return -1; | |
660 | if (ga->ngroups > gb->ngroups) | |
661 | return 1; | |
662 | ||
663 | for (g = 0; g < ga->ngroups; g++) { | |
664 | if (gid_lt(ga->gid[g], gb->gid[g])) | |
665 | return -1; | |
666 | if (gid_gt(ga->gid[g], gb->gid[g])) | |
667 | return 1; | |
668 | } | |
669 | return 0; | |
670 | } | |
671 | EXPORT_SYMBOL(cred_fscmp); | |
672 | ||
905ae01c AG |
673 | int set_cred_ucounts(struct cred *new) |
674 | { | |
34dc2fd6 | 675 | struct ucounts *new_ucounts, *old_ucounts = new->ucounts; |
905ae01c | 676 | |
905ae01c AG |
677 | /* |
678 | * This optimization is needed because alloc_ucounts() uses locks | |
679 | * for table lookups. | |
680 | */ | |
a55d0729 | 681 | if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->uid)) |
905ae01c AG |
682 | return 0; |
683 | ||
a55d0729 | 684 | if (!(new_ucounts = alloc_ucounts(new->user_ns, new->uid))) |
905ae01c AG |
685 | return -EAGAIN; |
686 | ||
34dc2fd6 | 687 | new->ucounts = new_ucounts; |
99c31f9f | 688 | put_ucounts(old_ucounts); |
905ae01c AG |
689 | |
690 | return 0; | |
691 | } | |
692 | ||
d84f4f99 DH |
693 | /* |
694 | * initialise the credentials stuff | |
695 | */ | |
696 | void __init cred_init(void) | |
697 | { | |
698 | /* allocate a slab in which we can store credentials */ | |
5d097056 VD |
699 | cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0, |
700 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); | |
d84f4f99 | 701 | } |
3a3b7ce9 DH |
702 | |
703 | /** | |
704 | * prepare_kernel_cred - Prepare a set of credentials for a kernel service | |
705 | * @daemon: A userspace daemon to be used as a reference | |
706 | * | |
707 | * Prepare a set of credentials for a kernel service. This can then be used to | |
708 | * override a task's own credentials so that work can be done on behalf of that | |
709 | * task that requires a different subjective context. | |
710 | * | |
5a17f040 KC |
711 | * @daemon is used to provide a base cred, with the security data derived from |
712 | * that; if this is "&init_task", they'll be set to 0, no groups, full | |
713 | * capabilities, and no keys. | |
3a3b7ce9 DH |
714 | * |
715 | * The caller may change these controls afterwards if desired. | |
716 | * | |
717 | * Returns the new credentials or NULL if out of memory. | |
3a3b7ce9 DH |
718 | */ |
719 | struct cred *prepare_kernel_cred(struct task_struct *daemon) | |
720 | { | |
721 | const struct cred *old; | |
722 | struct cred *new; | |
723 | ||
5a17f040 KC |
724 | if (WARN_ON_ONCE(!daemon)) |
725 | return NULL; | |
726 | ||
3a3b7ce9 DH |
727 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); |
728 | if (!new) | |
729 | return NULL; | |
730 | ||
e0e81739 DH |
731 | kdebug("prepare_kernel_cred() alloc %p", new); |
732 | ||
5a17f040 | 733 | old = get_task_cred(daemon); |
e0e81739 DH |
734 | validate_creds(old); |
735 | ||
43529c97 | 736 | *new = *old; |
d7852fbd | 737 | new->non_rcu = 0; |
fb2b2a1d TH |
738 | atomic_set(&new->usage, 1); |
739 | set_cred_subscribers(new, 0); | |
3a3b7ce9 | 740 | get_uid(new->user); |
0093ccb6 | 741 | get_user_ns(new->user_ns); |
3a3b7ce9 DH |
742 | get_group_info(new->group_info); |
743 | ||
744 | #ifdef CONFIG_KEYS | |
3a50597d DH |
745 | new->session_keyring = NULL; |
746 | new->process_keyring = NULL; | |
3a3b7ce9 | 747 | new->thread_keyring = NULL; |
3a50597d | 748 | new->request_key_auth = NULL; |
3a3b7ce9 DH |
749 | new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; |
750 | #endif | |
751 | ||
752 | #ifdef CONFIG_SECURITY | |
753 | new->security = NULL; | |
754 | #endif | |
905ae01c AG |
755 | new->ucounts = get_ucounts(new->ucounts); |
756 | if (!new->ucounts) | |
757 | goto error; | |
758 | ||
bbb6d0f3 AG |
759 | if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) |
760 | goto error; | |
761 | ||
3a3b7ce9 | 762 | put_cred(old); |
e0e81739 | 763 | validate_creds(new); |
3a3b7ce9 DH |
764 | return new; |
765 | ||
766 | error: | |
767 | put_cred(new); | |
0de33681 | 768 | put_cred(old); |
3a3b7ce9 DH |
769 | return NULL; |
770 | } | |
771 | EXPORT_SYMBOL(prepare_kernel_cred); | |
772 | ||
773 | /** | |
774 | * set_security_override - Set the security ID in a set of credentials | |
775 | * @new: The credentials to alter | |
776 | * @secid: The LSM security ID to set | |
777 | * | |
778 | * Set the LSM security ID in a set of credentials so that the subjective | |
779 | * security is overridden when an alternative set of credentials is used. | |
780 | */ | |
781 | int set_security_override(struct cred *new, u32 secid) | |
782 | { | |
783 | return security_kernel_act_as(new, secid); | |
784 | } | |
785 | EXPORT_SYMBOL(set_security_override); | |
786 | ||
787 | /** | |
788 | * set_security_override_from_ctx - Set the security ID in a set of credentials | |
789 | * @new: The credentials to alter | |
790 | * @secctx: The LSM security context to generate the security ID from. | |
791 | * | |
792 | * Set the LSM security ID in a set of credentials so that the subjective | |
793 | * security is overridden when an alternative set of credentials is used. The | |
794 | * security ID is specified in string form as a security context to be | |
795 | * interpreted by the LSM. | |
796 | */ | |
797 | int set_security_override_from_ctx(struct cred *new, const char *secctx) | |
798 | { | |
799 | u32 secid; | |
800 | int ret; | |
801 | ||
802 | ret = security_secctx_to_secid(secctx, strlen(secctx), &secid); | |
803 | if (ret < 0) | |
804 | return ret; | |
805 | ||
806 | return set_security_override(new, secid); | |
807 | } | |
808 | EXPORT_SYMBOL(set_security_override_from_ctx); | |
809 | ||
810 | /** | |
811 | * set_create_files_as - Set the LSM file create context in a set of credentials | |
812 | * @new: The credentials to alter | |
813 | * @inode: The inode to take the context from | |
814 | * | |
815 | * Change the LSM file creation context in a set of credentials to be the same | |
816 | * as the object context of the specified inode, so that the new inodes have | |
817 | * the same MAC context as that inode. | |
818 | */ | |
819 | int set_create_files_as(struct cred *new, struct inode *inode) | |
820 | { | |
5f65e5ca SF |
821 | if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid)) |
822 | return -EINVAL; | |
3a3b7ce9 DH |
823 | new->fsuid = inode->i_uid; |
824 | new->fsgid = inode->i_gid; | |
825 | return security_kernel_create_files_as(new, inode); | |
826 | } | |
827 | EXPORT_SYMBOL(set_create_files_as); | |
e0e81739 DH |
828 | |
829 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
830 | ||
74908a00 AM |
831 | bool creds_are_invalid(const struct cred *cred) |
832 | { | |
833 | if (cred->magic != CRED_MAGIC) | |
834 | return true; | |
74908a00 AM |
835 | return false; |
836 | } | |
764db03f | 837 | EXPORT_SYMBOL(creds_are_invalid); |
74908a00 | 838 | |
e0e81739 DH |
839 | /* |
840 | * dump invalid credentials | |
841 | */ | |
842 | static void dump_invalid_creds(const struct cred *cred, const char *label, | |
843 | const struct task_struct *tsk) | |
844 | { | |
4099451a | 845 | pr_err("%s credentials: %p %s%s%s\n", |
e0e81739 DH |
846 | label, cred, |
847 | cred == &init_cred ? "[init]" : "", | |
848 | cred == tsk->real_cred ? "[real]" : "", | |
849 | cred == tsk->cred ? "[eff]" : ""); | |
4099451a | 850 | pr_err("->magic=%x, put_addr=%p\n", |
e0e81739 | 851 | cred->magic, cred->put_addr); |
4099451a | 852 | pr_err("->usage=%d, subscr=%d\n", |
e0e81739 DH |
853 | atomic_read(&cred->usage), |
854 | read_cred_subscribers(cred)); | |
4099451a | 855 | pr_err("->*uid = { %d,%d,%d,%d }\n", |
c9235f48 EB |
856 | from_kuid_munged(&init_user_ns, cred->uid), |
857 | from_kuid_munged(&init_user_ns, cred->euid), | |
858 | from_kuid_munged(&init_user_ns, cred->suid), | |
859 | from_kuid_munged(&init_user_ns, cred->fsuid)); | |
4099451a | 860 | pr_err("->*gid = { %d,%d,%d,%d }\n", |
c9235f48 EB |
861 | from_kgid_munged(&init_user_ns, cred->gid), |
862 | from_kgid_munged(&init_user_ns, cred->egid), | |
863 | from_kgid_munged(&init_user_ns, cred->sgid), | |
864 | from_kgid_munged(&init_user_ns, cred->fsgid)); | |
e0e81739 | 865 | #ifdef CONFIG_SECURITY |
4099451a | 866 | pr_err("->security is %p\n", cred->security); |
e0e81739 DH |
867 | if ((unsigned long) cred->security >= PAGE_SIZE && |
868 | (((unsigned long) cred->security & 0xffffff00) != | |
869 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))) | |
4099451a | 870 | pr_err("->security {%x, %x}\n", |
e0e81739 DH |
871 | ((u32*)cred->security)[0], |
872 | ((u32*)cred->security)[1]); | |
873 | #endif | |
874 | } | |
875 | ||
876 | /* | |
877 | * report use of invalid credentials | |
878 | */ | |
105cd685 | 879 | void __noreturn __invalid_creds(const struct cred *cred, const char *file, unsigned line) |
e0e81739 | 880 | { |
4099451a | 881 | pr_err("Invalid credentials\n"); |
882 | pr_err("At %s:%u\n", file, line); | |
e0e81739 DH |
883 | dump_invalid_creds(cred, "Specified", current); |
884 | BUG(); | |
885 | } | |
886 | EXPORT_SYMBOL(__invalid_creds); | |
887 | ||
888 | /* | |
889 | * check the credentials on a process | |
890 | */ | |
891 | void __validate_process_creds(struct task_struct *tsk, | |
892 | const char *file, unsigned line) | |
893 | { | |
894 | if (tsk->cred == tsk->real_cred) { | |
895 | if (unlikely(read_cred_subscribers(tsk->cred) < 2 || | |
896 | creds_are_invalid(tsk->cred))) | |
897 | goto invalid_creds; | |
898 | } else { | |
899 | if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 || | |
900 | read_cred_subscribers(tsk->cred) < 1 || | |
901 | creds_are_invalid(tsk->real_cred) || | |
902 | creds_are_invalid(tsk->cred))) | |
903 | goto invalid_creds; | |
904 | } | |
905 | return; | |
906 | ||
907 | invalid_creds: | |
4099451a | 908 | pr_err("Invalid process credentials\n"); |
909 | pr_err("At %s:%u\n", file, line); | |
e0e81739 DH |
910 | |
911 | dump_invalid_creds(tsk->real_cred, "Real", tsk); | |
912 | if (tsk->cred != tsk->real_cred) | |
913 | dump_invalid_creds(tsk->cred, "Effective", tsk); | |
914 | else | |
4099451a | 915 | pr_err("Effective creds == Real creds\n"); |
e0e81739 DH |
916 | BUG(); |
917 | } | |
918 | EXPORT_SYMBOL(__validate_process_creds); | |
919 | ||
920 | /* | |
921 | * check creds for do_exit() | |
922 | */ | |
923 | void validate_creds_for_do_exit(struct task_struct *tsk) | |
924 | { | |
925 | kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})", | |
926 | tsk->real_cred, tsk->cred, | |
927 | atomic_read(&tsk->cred->usage), | |
928 | read_cred_subscribers(tsk->cred)); | |
929 | ||
930 | __validate_process_creds(tsk, __FILE__, __LINE__); | |
931 | } | |
932 | ||
933 | #endif /* CONFIG_DEBUG_CREDENTIALS */ |