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af777cd1 | 1 | /* Task credentials management - see Documentation/security/credentials.rst |
f1752eec DH |
2 | * |
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 | */ | |
9984de1a | 11 | #include <linux/export.h> |
f1752eec | 12 | #include <linux/cred.h> |
5a0e3ad6 | 13 | #include <linux/slab.h> |
f1752eec | 14 | #include <linux/sched.h> |
f7ccbae4 | 15 | #include <linux/sched/coredump.h> |
f1752eec DH |
16 | #include <linux/key.h> |
17 | #include <linux/keyctl.h> | |
18 | #include <linux/init_task.h> | |
19 | #include <linux/security.h> | |
40401530 | 20 | #include <linux/binfmts.h> |
d84f4f99 | 21 | #include <linux/cn_proc.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 IM |
38 | /* init to 2 - one for init_task, one to ensure it is never freed */ |
39 | struct group_info init_groups = { .usage = ATOMIC_INIT(2) }; | |
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 DH |
65 | .group_info = &init_groups, |
66 | }; | |
67 | ||
e0e81739 DH |
68 | static 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 | ||
75 | static 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 | ||
84 | static 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 | ||
f1752eec DH |
93 | /* |
94 | * The RCU callback to actually dispose of a set of credentials | |
95 | */ | |
96 | static void put_cred_rcu(struct rcu_head *rcu) | |
97 | { | |
98 | struct cred *cred = container_of(rcu, struct cred, rcu); | |
99 | ||
e0e81739 DH |
100 | 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 | |
d84f4f99 DH |
112 | if (atomic_read(&cred->usage) != 0) |
113 | panic("CRED: put_cred_rcu() sees %p with usage %d\n", | |
114 | cred, atomic_read(&cred->usage)); | |
e0e81739 | 115 | #endif |
f1752eec | 116 | |
d84f4f99 | 117 | security_cred_free(cred); |
3a50597d DH |
118 | key_put(cred->session_keyring); |
119 | key_put(cred->process_keyring); | |
f1752eec DH |
120 | key_put(cred->thread_keyring); |
121 | key_put(cred->request_key_auth); | |
4a5d6ba1 DH |
122 | if (cred->group_info) |
123 | put_group_info(cred->group_info); | |
f1752eec | 124 | free_uid(cred->user); |
0093ccb6 | 125 | put_user_ns(cred->user_ns); |
d84f4f99 | 126 | kmem_cache_free(cred_jar, cred); |
f1752eec DH |
127 | } |
128 | ||
129 | /** | |
130 | * __put_cred - Destroy a set of credentials | |
d84f4f99 | 131 | * @cred: The record to release |
f1752eec DH |
132 | * |
133 | * Destroy a set of credentials on which no references remain. | |
134 | */ | |
135 | void __put_cred(struct cred *cred) | |
136 | { | |
e0e81739 DH |
137 | kdebug("__put_cred(%p{%d,%d})", cred, |
138 | atomic_read(&cred->usage), | |
139 | read_cred_subscribers(cred)); | |
140 | ||
d84f4f99 | 141 | BUG_ON(atomic_read(&cred->usage) != 0); |
e0e81739 DH |
142 | #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); | |
d84f4f99 | 149 | |
84e96ba9 LT |
150 | if (cred->non_rcu) |
151 | put_cred_rcu(&cred->rcu); | |
152 | else | |
153 | call_rcu(&cred->rcu, put_cred_rcu); | |
f1752eec DH |
154 | } |
155 | EXPORT_SYMBOL(__put_cred); | |
156 | ||
e0e81739 DH |
157 | /* |
158 | * Clean up a task's credentials when it exits | |
159 | */ | |
160 | void 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); | |
ee18d64c DH |
179 | } |
180 | ||
de09a977 DH |
181 | /** |
182 | * get_task_cred - Get another task's objective credentials | |
183 | * @task: The task to query | |
184 | * | |
185 | * Get the objective credentials of a task, pinning them so that they can't go | |
186 | * away. Accessing a task's credentials directly is not permitted. | |
187 | * | |
188 | * The caller must also make sure task doesn't get deleted, either by holding a | |
189 | * ref on task or by holding tasklist_lock to prevent it from being unlinked. | |
190 | */ | |
191 | const struct cred *get_task_cred(struct task_struct *task) | |
192 | { | |
193 | const struct cred *cred; | |
194 | ||
195 | rcu_read_lock(); | |
196 | ||
197 | do { | |
198 | cred = __task_cred((task)); | |
199 | BUG_ON(!cred); | |
200 | } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage)); | |
201 | ||
202 | rcu_read_unlock(); | |
203 | return cred; | |
204 | } | |
205 | ||
ee18d64c DH |
206 | /* |
207 | * Allocate blank credentials, such that the credentials can be filled in at a | |
208 | * later date without risk of ENOMEM. | |
209 | */ | |
210 | struct cred *cred_alloc_blank(void) | |
211 | { | |
212 | struct cred *new; | |
213 | ||
214 | new = kmem_cache_zalloc(cred_jar, GFP_KERNEL); | |
215 | if (!new) | |
216 | return NULL; | |
217 | ||
ee18d64c | 218 | atomic_set(&new->usage, 1); |
2edeaa34 TH |
219 | #ifdef CONFIG_DEBUG_CREDENTIALS |
220 | new->magic = CRED_MAGIC; | |
221 | #endif | |
ee18d64c DH |
222 | |
223 | if (security_cred_alloc_blank(new, GFP_KERNEL) < 0) | |
224 | goto error; | |
225 | ||
ee18d64c DH |
226 | return new; |
227 | ||
228 | error: | |
229 | abort_creds(new); | |
230 | return NULL; | |
e0e81739 DH |
231 | } |
232 | ||
d84f4f99 DH |
233 | /** |
234 | * prepare_creds - Prepare a new set of credentials for modification | |
235 | * | |
236 | * Prepare a new set of task credentials for modification. A task's creds | |
237 | * shouldn't generally be modified directly, therefore this function is used to | |
238 | * prepare a new copy, which the caller then modifies and then commits by | |
239 | * calling commit_creds(). | |
240 | * | |
3b11a1de DH |
241 | * Preparation involves making a copy of the objective creds for modification. |
242 | * | |
d84f4f99 DH |
243 | * Returns a pointer to the new creds-to-be if successful, NULL otherwise. |
244 | * | |
245 | * Call commit_creds() or abort_creds() to clean up. | |
246 | */ | |
247 | struct cred *prepare_creds(void) | |
248 | { | |
249 | struct task_struct *task = current; | |
250 | const struct cred *old; | |
251 | struct cred *new; | |
252 | ||
e0e81739 | 253 | validate_process_creds(); |
d84f4f99 DH |
254 | |
255 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); | |
256 | if (!new) | |
257 | return NULL; | |
258 | ||
e0e81739 DH |
259 | kdebug("prepare_creds() alloc %p", new); |
260 | ||
d84f4f99 DH |
261 | old = task->cred; |
262 | memcpy(new, old, sizeof(struct cred)); | |
263 | ||
84e96ba9 | 264 | new->non_rcu = 0; |
d84f4f99 | 265 | atomic_set(&new->usage, 1); |
e0e81739 | 266 | set_cred_subscribers(new, 0); |
d84f4f99 DH |
267 | get_group_info(new->group_info); |
268 | get_uid(new->user); | |
0093ccb6 | 269 | get_user_ns(new->user_ns); |
d84f4f99 DH |
270 | |
271 | #ifdef CONFIG_KEYS | |
3a50597d DH |
272 | key_get(new->session_keyring); |
273 | key_get(new->process_keyring); | |
d84f4f99 DH |
274 | key_get(new->thread_keyring); |
275 | key_get(new->request_key_auth); | |
d84f4f99 DH |
276 | #endif |
277 | ||
278 | #ifdef CONFIG_SECURITY | |
279 | new->security = NULL; | |
280 | #endif | |
281 | ||
282 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) | |
283 | goto error; | |
e0e81739 | 284 | validate_creds(new); |
d84f4f99 DH |
285 | return new; |
286 | ||
287 | error: | |
288 | abort_creds(new); | |
289 | return NULL; | |
290 | } | |
291 | EXPORT_SYMBOL(prepare_creds); | |
292 | ||
a6f76f23 DH |
293 | /* |
294 | * Prepare credentials for current to perform an execve() | |
9b1bf12d | 295 | * - The caller must hold ->cred_guard_mutex |
a6f76f23 DH |
296 | */ |
297 | struct cred *prepare_exec_creds(void) | |
298 | { | |
a6f76f23 DH |
299 | struct cred *new; |
300 | ||
a6f76f23 | 301 | new = prepare_creds(); |
3a50597d | 302 | if (!new) |
a6f76f23 | 303 | return new; |
a6f76f23 DH |
304 | |
305 | #ifdef CONFIG_KEYS | |
306 | /* newly exec'd tasks don't get a thread keyring */ | |
307 | key_put(new->thread_keyring); | |
308 | new->thread_keyring = NULL; | |
309 | ||
a6f76f23 | 310 | /* inherit the session keyring; new process keyring */ |
3a50597d DH |
311 | key_put(new->process_keyring); |
312 | new->process_keyring = NULL; | |
a6f76f23 DH |
313 | #endif |
314 | ||
315 | return new; | |
316 | } | |
317 | ||
f1752eec DH |
318 | /* |
319 | * Copy credentials for the new process created by fork() | |
d84f4f99 DH |
320 | * |
321 | * We share if we can, but under some circumstances we have to generate a new | |
322 | * set. | |
3b11a1de DH |
323 | * |
324 | * The new process gets the current process's subjective credentials as its | |
325 | * objective and subjective credentials | |
f1752eec DH |
326 | */ |
327 | int copy_creds(struct task_struct *p, unsigned long clone_flags) | |
328 | { | |
d84f4f99 | 329 | struct cred *new; |
18b6e041 | 330 | int ret; |
d84f4f99 | 331 | |
d84f4f99 DH |
332 | if ( |
333 | #ifdef CONFIG_KEYS | |
334 | !p->cred->thread_keyring && | |
335 | #endif | |
336 | clone_flags & CLONE_THREAD | |
337 | ) { | |
3b11a1de | 338 | p->real_cred = get_cred(p->cred); |
d84f4f99 | 339 | get_cred(p->cred); |
e0e81739 DH |
340 | alter_cred_subscribers(p->cred, 2); |
341 | kdebug("share_creds(%p{%d,%d})", | |
342 | p->cred, atomic_read(&p->cred->usage), | |
343 | read_cred_subscribers(p->cred)); | |
d84f4f99 DH |
344 | atomic_inc(&p->cred->user->processes); |
345 | return 0; | |
346 | } | |
347 | ||
348 | new = prepare_creds(); | |
349 | if (!new) | |
f1752eec DH |
350 | return -ENOMEM; |
351 | ||
18b6e041 SH |
352 | if (clone_flags & CLONE_NEWUSER) { |
353 | ret = create_user_ns(new); | |
354 | if (ret < 0) | |
355 | goto error_put; | |
356 | } | |
357 | ||
bb952bb9 | 358 | #ifdef CONFIG_KEYS |
d84f4f99 DH |
359 | /* new threads get their own thread keyrings if their parent already |
360 | * had one */ | |
361 | if (new->thread_keyring) { | |
362 | key_put(new->thread_keyring); | |
363 | new->thread_keyring = NULL; | |
364 | if (clone_flags & CLONE_THREAD) | |
365 | install_thread_keyring_to_cred(new); | |
366 | } | |
367 | ||
3a50597d DH |
368 | /* The process keyring is only shared between the threads in a process; |
369 | * anything outside of those threads doesn't inherit. | |
370 | */ | |
d84f4f99 | 371 | if (!(clone_flags & CLONE_THREAD)) { |
3a50597d DH |
372 | key_put(new->process_keyring); |
373 | new->process_keyring = NULL; | |
bb952bb9 DH |
374 | } |
375 | #endif | |
376 | ||
d84f4f99 | 377 | atomic_inc(&new->user->processes); |
3b11a1de | 378 | p->cred = p->real_cred = get_cred(new); |
e0e81739 DH |
379 | alter_cred_subscribers(new, 2); |
380 | validate_creds(new); | |
d84f4f99 | 381 | return 0; |
18b6e041 SH |
382 | |
383 | error_put: | |
384 | put_cred(new); | |
385 | return ret; | |
d84f4f99 | 386 | } |
f1752eec | 387 | |
aa6d054e EB |
388 | static bool cred_cap_issubset(const struct cred *set, const struct cred *subset) |
389 | { | |
390 | const struct user_namespace *set_ns = set->user_ns; | |
391 | const struct user_namespace *subset_ns = subset->user_ns; | |
392 | ||
393 | /* If the two credentials are in the same user namespace see if | |
394 | * the capabilities of subset are a subset of set. | |
395 | */ | |
396 | if (set_ns == subset_ns) | |
397 | return cap_issubset(subset->cap_permitted, set->cap_permitted); | |
398 | ||
399 | /* The credentials are in a different user namespaces | |
400 | * therefore one is a subset of the other only if a set is an | |
401 | * ancestor of subset and set->euid is owner of subset or one | |
402 | * of subsets ancestors. | |
403 | */ | |
404 | for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) { | |
405 | if ((set_ns == subset_ns->parent) && | |
406 | uid_eq(subset_ns->owner, set->euid)) | |
407 | return true; | |
408 | } | |
409 | ||
410 | return false; | |
411 | } | |
412 | ||
d84f4f99 DH |
413 | /** |
414 | * commit_creds - Install new credentials upon the current task | |
415 | * @new: The credentials to be assigned | |
416 | * | |
417 | * Install a new set of credentials to the current task, using RCU to replace | |
3b11a1de DH |
418 | * the old set. Both the objective and the subjective credentials pointers are |
419 | * updated. This function may not be called if the subjective credentials are | |
420 | * in an overridden state. | |
d84f4f99 DH |
421 | * |
422 | * This function eats the caller's reference to the new credentials. | |
423 | * | |
424 | * Always returns 0 thus allowing this function to be tail-called at the end | |
425 | * of, say, sys_setgid(). | |
426 | */ | |
427 | int commit_creds(struct cred *new) | |
428 | { | |
429 | struct task_struct *task = current; | |
e0e81739 | 430 | const struct cred *old = task->real_cred; |
d84f4f99 | 431 | |
e0e81739 DH |
432 | kdebug("commit_creds(%p{%d,%d})", new, |
433 | atomic_read(&new->usage), | |
434 | read_cred_subscribers(new)); | |
435 | ||
436 | BUG_ON(task->cred != old); | |
437 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
438 | BUG_ON(read_cred_subscribers(old) < 2); | |
439 | validate_creds(old); | |
440 | validate_creds(new); | |
441 | #endif | |
d84f4f99 | 442 | BUG_ON(atomic_read(&new->usage) < 1); |
d84f4f99 | 443 | |
3b11a1de DH |
444 | get_cred(new); /* we will require a ref for the subj creds too */ |
445 | ||
d84f4f99 | 446 | /* dumpability changes */ |
078de5f7 EB |
447 | if (!uid_eq(old->euid, new->euid) || |
448 | !gid_eq(old->egid, new->egid) || | |
449 | !uid_eq(old->fsuid, new->fsuid) || | |
450 | !gid_eq(old->fsgid, new->fsgid) || | |
aa6d054e | 451 | !cred_cap_issubset(old, new)) { |
b9456371 DH |
452 | if (task->mm) |
453 | set_dumpable(task->mm, suid_dumpable); | |
d84f4f99 | 454 | task->pdeath_signal = 0; |
c3acb19a JH |
455 | /* |
456 | * If a task drops privileges and becomes nondumpable, | |
457 | * the dumpability change must become visible before | |
458 | * the credential change; otherwise, a __ptrace_may_access() | |
459 | * racing with this change may be able to attach to a task it | |
460 | * shouldn't be able to attach to (as if the task had dropped | |
461 | * privileges without becoming nondumpable). | |
462 | * Pairs with a read barrier in __ptrace_may_access(). | |
463 | */ | |
d84f4f99 | 464 | smp_wmb(); |
f1752eec DH |
465 | } |
466 | ||
d84f4f99 | 467 | /* alter the thread keyring */ |
078de5f7 | 468 | if (!uid_eq(new->fsuid, old->fsuid)) |
d84f4f99 | 469 | key_fsuid_changed(task); |
078de5f7 | 470 | if (!gid_eq(new->fsgid, old->fsgid)) |
d84f4f99 DH |
471 | key_fsgid_changed(task); |
472 | ||
473 | /* do it | |
72fa5997 VK |
474 | * RLIMIT_NPROC limits on user->processes have already been checked |
475 | * in set_user(). | |
d84f4f99 | 476 | */ |
e0e81739 | 477 | alter_cred_subscribers(new, 2); |
d84f4f99 DH |
478 | if (new->user != old->user) |
479 | atomic_inc(&new->user->processes); | |
3b11a1de | 480 | rcu_assign_pointer(task->real_cred, new); |
d84f4f99 DH |
481 | rcu_assign_pointer(task->cred, new); |
482 | if (new->user != old->user) | |
483 | atomic_dec(&old->user->processes); | |
e0e81739 | 484 | alter_cred_subscribers(old, -2); |
d84f4f99 | 485 | |
d84f4f99 | 486 | /* send notifications */ |
078de5f7 EB |
487 | if (!uid_eq(new->uid, old->uid) || |
488 | !uid_eq(new->euid, old->euid) || | |
489 | !uid_eq(new->suid, old->suid) || | |
490 | !uid_eq(new->fsuid, old->fsuid)) | |
d84f4f99 | 491 | proc_id_connector(task, PROC_EVENT_UID); |
f1752eec | 492 | |
078de5f7 EB |
493 | if (!gid_eq(new->gid, old->gid) || |
494 | !gid_eq(new->egid, old->egid) || | |
495 | !gid_eq(new->sgid, old->sgid) || | |
496 | !gid_eq(new->fsgid, old->fsgid)) | |
d84f4f99 | 497 | proc_id_connector(task, PROC_EVENT_GID); |
f1752eec | 498 | |
3b11a1de DH |
499 | /* release the old obj and subj refs both */ |
500 | put_cred(old); | |
d84f4f99 | 501 | put_cred(old); |
f1752eec DH |
502 | return 0; |
503 | } | |
d84f4f99 DH |
504 | EXPORT_SYMBOL(commit_creds); |
505 | ||
506 | /** | |
507 | * abort_creds - Discard a set of credentials and unlock the current task | |
508 | * @new: The credentials that were going to be applied | |
509 | * | |
510 | * Discard a set of credentials that were under construction and unlock the | |
511 | * current task. | |
512 | */ | |
513 | void abort_creds(struct cred *new) | |
514 | { | |
e0e81739 DH |
515 | kdebug("abort_creds(%p{%d,%d})", new, |
516 | atomic_read(&new->usage), | |
517 | read_cred_subscribers(new)); | |
518 | ||
519 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
520 | BUG_ON(read_cred_subscribers(new) != 0); | |
521 | #endif | |
d84f4f99 DH |
522 | BUG_ON(atomic_read(&new->usage) < 1); |
523 | put_cred(new); | |
524 | } | |
525 | EXPORT_SYMBOL(abort_creds); | |
526 | ||
527 | /** | |
3b11a1de | 528 | * override_creds - Override the current process's subjective credentials |
d84f4f99 DH |
529 | * @new: The credentials to be assigned |
530 | * | |
3b11a1de DH |
531 | * Install a set of temporary override subjective credentials on the current |
532 | * process, returning the old set for later reversion. | |
d84f4f99 DH |
533 | */ |
534 | const struct cred *override_creds(const struct cred *new) | |
535 | { | |
536 | const struct cred *old = current->cred; | |
537 | ||
e0e81739 DH |
538 | kdebug("override_creds(%p{%d,%d})", new, |
539 | atomic_read(&new->usage), | |
540 | read_cred_subscribers(new)); | |
541 | ||
542 | validate_creds(old); | |
543 | validate_creds(new); | |
84e96ba9 LT |
544 | |
545 | /* | |
546 | * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'. | |
547 | * | |
548 | * That means that we do not clear the 'non_rcu' flag, since | |
549 | * we are only installing the cred into the thread-synchronous | |
550 | * '->cred' pointer, not the '->real_cred' pointer that is | |
551 | * visible to other threads under RCU. | |
552 | * | |
553 | * Also note that we did validate_creds() manually, not depending | |
554 | * on the validation in 'get_cred()'. | |
555 | */ | |
556 | get_new_cred((struct cred *)new); | |
e0e81739 DH |
557 | alter_cred_subscribers(new, 1); |
558 | rcu_assign_pointer(current->cred, new); | |
559 | alter_cred_subscribers(old, -1); | |
560 | ||
561 | kdebug("override_creds() = %p{%d,%d}", old, | |
562 | atomic_read(&old->usage), | |
563 | read_cred_subscribers(old)); | |
d84f4f99 DH |
564 | return old; |
565 | } | |
566 | EXPORT_SYMBOL(override_creds); | |
567 | ||
568 | /** | |
3b11a1de | 569 | * revert_creds - Revert a temporary subjective credentials override |
d84f4f99 DH |
570 | * @old: The credentials to be restored |
571 | * | |
3b11a1de DH |
572 | * Revert a temporary set of override subjective credentials to an old set, |
573 | * discarding the override set. | |
d84f4f99 DH |
574 | */ |
575 | void revert_creds(const struct cred *old) | |
576 | { | |
577 | const struct cred *override = current->cred; | |
578 | ||
e0e81739 DH |
579 | kdebug("revert_creds(%p{%d,%d})", old, |
580 | atomic_read(&old->usage), | |
581 | read_cred_subscribers(old)); | |
582 | ||
583 | validate_creds(old); | |
584 | validate_creds(override); | |
585 | alter_cred_subscribers(old, 1); | |
d84f4f99 | 586 | rcu_assign_pointer(current->cred, old); |
e0e81739 | 587 | alter_cred_subscribers(override, -1); |
d84f4f99 DH |
588 | put_cred(override); |
589 | } | |
590 | EXPORT_SYMBOL(revert_creds); | |
591 | ||
592 | /* | |
593 | * initialise the credentials stuff | |
594 | */ | |
595 | void __init cred_init(void) | |
596 | { | |
597 | /* allocate a slab in which we can store credentials */ | |
5d097056 VD |
598 | cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0, |
599 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); | |
d84f4f99 | 600 | } |
3a3b7ce9 DH |
601 | |
602 | /** | |
750ab83b SF |
603 | * clone_cred - Create a new copy of a set of credentials |
604 | * @old: Credentials to be copied | |
3a3b7ce9 | 605 | * |
750ab83b SF |
606 | * Prepare a new set of credentials that is an exact copy of @old. This can |
607 | * optionally be modified and used to override a task's own credentials so | |
608 | * that work can be done on behalf of that task that requires a different | |
609 | * subjective context. | |
3a3b7ce9 | 610 | * |
750ab83b | 611 | * Returns the new credentials or NULL if @old is NULL or if out of memory. |
3a3b7ce9 DH |
612 | * |
613 | * Does not take, and does not return holding current->cred_replace_mutex. | |
614 | */ | |
750ab83b | 615 | struct cred *clone_cred(const struct cred *old) |
3a3b7ce9 | 616 | { |
3a3b7ce9 DH |
617 | struct cred *new; |
618 | ||
750ab83b SF |
619 | if (!old) |
620 | return NULL; | |
621 | ||
3a3b7ce9 DH |
622 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); |
623 | if (!new) | |
624 | return NULL; | |
625 | ||
750ab83b | 626 | kdebug("clone_cred() alloc %p", new); |
3a3b7ce9 | 627 | |
e0e81739 DH |
628 | validate_creds(old); |
629 | ||
43529c97 | 630 | *new = *old; |
84e96ba9 | 631 | new->non_rcu = 0; |
fb2b2a1d TH |
632 | atomic_set(&new->usage, 1); |
633 | set_cred_subscribers(new, 0); | |
3a3b7ce9 | 634 | get_uid(new->user); |
0093ccb6 | 635 | get_user_ns(new->user_ns); |
3a3b7ce9 DH |
636 | get_group_info(new->group_info); |
637 | ||
638 | #ifdef CONFIG_KEYS | |
3a50597d DH |
639 | new->session_keyring = NULL; |
640 | new->process_keyring = NULL; | |
3a3b7ce9 | 641 | new->thread_keyring = NULL; |
3a50597d | 642 | new->request_key_auth = NULL; |
3a3b7ce9 DH |
643 | new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; |
644 | #endif | |
645 | ||
646 | #ifdef CONFIG_SECURITY | |
647 | new->security = NULL; | |
648 | #endif | |
649 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) | |
650 | goto error; | |
651 | ||
e0e81739 | 652 | validate_creds(new); |
3a3b7ce9 DH |
653 | return new; |
654 | ||
655 | error: | |
656 | put_cred(new); | |
657 | return NULL; | |
658 | } | |
750ab83b SF |
659 | EXPORT_SYMBOL(clone_cred); |
660 | ||
661 | /** | |
662 | * prepare_kernel_cred - Prepare a set of credentials for a kernel service | |
663 | * @daemon: A userspace daemon to be used as a reference | |
664 | * | |
665 | * Prepare a set of credentials for a kernel service. This can then be used to | |
666 | * override a task's own credentials so that work can be done on behalf of that | |
667 | * task that requires a different subjective context. | |
668 | * | |
669 | * @daemon is used to provide a base for the security record, but can be NULL. | |
670 | * If @daemon is supplied, then the security data will be derived from that; | |
671 | * otherwise they'll be set to 0 and no groups, full capabilities and no keys. | |
672 | * | |
673 | * The caller may change these controls afterwards if desired. | |
674 | * | |
675 | * Returns the new credentials or NULL if out of memory. | |
676 | * | |
677 | * Does not take, and does not return holding current->cred_replace_mutex. | |
678 | */ | |
679 | struct cred *prepare_kernel_cred(struct task_struct *daemon) | |
680 | { | |
681 | const struct cred *old; | |
682 | struct cred *new; | |
683 | ||
684 | if (daemon) | |
685 | old = get_task_cred(daemon); | |
686 | else | |
687 | old = get_cred(&init_cred); | |
688 | ||
689 | new = clone_cred(old); | |
690 | put_cred(old); | |
691 | return new; | |
692 | } | |
3a3b7ce9 DH |
693 | EXPORT_SYMBOL(prepare_kernel_cred); |
694 | ||
695 | /** | |
696 | * set_security_override - Set the security ID in a set of credentials | |
697 | * @new: The credentials to alter | |
698 | * @secid: The LSM security ID to set | |
699 | * | |
700 | * Set the LSM security ID in a set of credentials so that the subjective | |
701 | * security is overridden when an alternative set of credentials is used. | |
702 | */ | |
703 | int set_security_override(struct cred *new, u32 secid) | |
704 | { | |
705 | return security_kernel_act_as(new, secid); | |
706 | } | |
707 | EXPORT_SYMBOL(set_security_override); | |
708 | ||
709 | /** | |
710 | * set_security_override_from_ctx - Set the security ID in a set of credentials | |
711 | * @new: The credentials to alter | |
712 | * @secctx: The LSM security context to generate the security ID from. | |
713 | * | |
714 | * Set the LSM security ID in a set of credentials so that the subjective | |
715 | * security is overridden when an alternative set of credentials is used. The | |
716 | * security ID is specified in string form as a security context to be | |
717 | * interpreted by the LSM. | |
718 | */ | |
719 | int set_security_override_from_ctx(struct cred *new, const char *secctx) | |
720 | { | |
721 | u32 secid; | |
722 | int ret; | |
723 | ||
724 | ret = security_secctx_to_secid(secctx, strlen(secctx), &secid); | |
725 | if (ret < 0) | |
726 | return ret; | |
727 | ||
728 | return set_security_override(new, secid); | |
729 | } | |
730 | EXPORT_SYMBOL(set_security_override_from_ctx); | |
731 | ||
732 | /** | |
733 | * set_create_files_as - Set the LSM file create context in a set of credentials | |
734 | * @new: The credentials to alter | |
735 | * @inode: The inode to take the context from | |
736 | * | |
737 | * Change the LSM file creation context in a set of credentials to be the same | |
738 | * as the object context of the specified inode, so that the new inodes have | |
739 | * the same MAC context as that inode. | |
740 | */ | |
741 | int set_create_files_as(struct cred *new, struct inode *inode) | |
742 | { | |
5f65e5ca SF |
743 | if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid)) |
744 | return -EINVAL; | |
3a3b7ce9 DH |
745 | new->fsuid = inode->i_uid; |
746 | new->fsgid = inode->i_gid; | |
747 | return security_kernel_create_files_as(new, inode); | |
748 | } | |
749 | EXPORT_SYMBOL(set_create_files_as); | |
e0e81739 DH |
750 | |
751 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
752 | ||
74908a00 AM |
753 | bool creds_are_invalid(const struct cred *cred) |
754 | { | |
755 | if (cred->magic != CRED_MAGIC) | |
756 | return true; | |
74908a00 AM |
757 | return false; |
758 | } | |
764db03f | 759 | EXPORT_SYMBOL(creds_are_invalid); |
74908a00 | 760 | |
e0e81739 DH |
761 | /* |
762 | * dump invalid credentials | |
763 | */ | |
764 | static void dump_invalid_creds(const struct cred *cred, const char *label, | |
765 | const struct task_struct *tsk) | |
766 | { | |
767 | printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n", | |
768 | label, cred, | |
769 | cred == &init_cred ? "[init]" : "", | |
770 | cred == tsk->real_cred ? "[real]" : "", | |
771 | cred == tsk->cred ? "[eff]" : ""); | |
772 | printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n", | |
773 | cred->magic, cred->put_addr); | |
774 | printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n", | |
775 | atomic_read(&cred->usage), | |
776 | read_cred_subscribers(cred)); | |
777 | printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n", | |
c9235f48 EB |
778 | from_kuid_munged(&init_user_ns, cred->uid), |
779 | from_kuid_munged(&init_user_ns, cred->euid), | |
780 | from_kuid_munged(&init_user_ns, cred->suid), | |
781 | from_kuid_munged(&init_user_ns, cred->fsuid)); | |
e0e81739 | 782 | printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n", |
c9235f48 EB |
783 | from_kgid_munged(&init_user_ns, cred->gid), |
784 | from_kgid_munged(&init_user_ns, cred->egid), | |
785 | from_kgid_munged(&init_user_ns, cred->sgid), | |
786 | from_kgid_munged(&init_user_ns, cred->fsgid)); | |
e0e81739 DH |
787 | #ifdef CONFIG_SECURITY |
788 | printk(KERN_ERR "CRED: ->security is %p\n", cred->security); | |
789 | if ((unsigned long) cred->security >= PAGE_SIZE && | |
790 | (((unsigned long) cred->security & 0xffffff00) != | |
791 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))) | |
792 | printk(KERN_ERR "CRED: ->security {%x, %x}\n", | |
793 | ((u32*)cred->security)[0], | |
794 | ((u32*)cred->security)[1]); | |
795 | #endif | |
796 | } | |
797 | ||
798 | /* | |
799 | * report use of invalid credentials | |
800 | */ | |
801 | void __invalid_creds(const struct cred *cred, const char *file, unsigned line) | |
802 | { | |
803 | printk(KERN_ERR "CRED: Invalid credentials\n"); | |
804 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); | |
805 | dump_invalid_creds(cred, "Specified", current); | |
806 | BUG(); | |
807 | } | |
808 | EXPORT_SYMBOL(__invalid_creds); | |
809 | ||
810 | /* | |
811 | * check the credentials on a process | |
812 | */ | |
813 | void __validate_process_creds(struct task_struct *tsk, | |
814 | const char *file, unsigned line) | |
815 | { | |
816 | if (tsk->cred == tsk->real_cred) { | |
817 | if (unlikely(read_cred_subscribers(tsk->cred) < 2 || | |
818 | creds_are_invalid(tsk->cred))) | |
819 | goto invalid_creds; | |
820 | } else { | |
821 | if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 || | |
822 | read_cred_subscribers(tsk->cred) < 1 || | |
823 | creds_are_invalid(tsk->real_cred) || | |
824 | creds_are_invalid(tsk->cred))) | |
825 | goto invalid_creds; | |
826 | } | |
827 | return; | |
828 | ||
829 | invalid_creds: | |
830 | printk(KERN_ERR "CRED: Invalid process credentials\n"); | |
831 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); | |
832 | ||
833 | dump_invalid_creds(tsk->real_cred, "Real", tsk); | |
834 | if (tsk->cred != tsk->real_cred) | |
835 | dump_invalid_creds(tsk->cred, "Effective", tsk); | |
836 | else | |
837 | printk(KERN_ERR "CRED: Effective creds == Real creds\n"); | |
838 | BUG(); | |
839 | } | |
840 | EXPORT_SYMBOL(__validate_process_creds); | |
841 | ||
842 | /* | |
843 | * check creds for do_exit() | |
844 | */ | |
845 | void validate_creds_for_do_exit(struct task_struct *tsk) | |
846 | { | |
847 | kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})", | |
848 | tsk->real_cred, tsk->cred, | |
849 | atomic_read(&tsk->cred->usage), | |
850 | read_cred_subscribers(tsk->cred)); | |
851 | ||
852 | __validate_process_creds(tsk, __FILE__, __LINE__); | |
853 | } | |
854 | ||
855 | #endif /* CONFIG_DEBUG_CREDENTIALS */ |