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1 : : // SPDX-License-Identifier: GPL-2.0-or-later
2 : : /* Task credentials management - see Documentation/security/credentials.rst
3 : : *
4 : : * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
5 : : * Written by David Howells (dhowells@redhat.com)
6 : : */
7 : : #include <linux/export.h>
8 : : #include <linux/cred.h>
9 : : #include <linux/slab.h>
10 : : #include <linux/sched.h>
11 : : #include <linux/sched/coredump.h>
12 : : #include <linux/key.h>
13 : : #include <linux/keyctl.h>
14 : : #include <linux/init_task.h>
15 : : #include <linux/security.h>
16 : : #include <linux/binfmts.h>
17 : : #include <linux/cn_proc.h>
18 : : #include <linux/uidgid.h>
19 : :
20 : : #if 0
21 : : #define kdebug(FMT, ...) \
22 : : printk("[%-5.5s%5u] " FMT "\n", \
23 : : current->comm, current->pid, ##__VA_ARGS__)
24 : : #else
25 : : #define kdebug(FMT, ...) \
26 : : do { \
27 : : if (0) \
28 : : no_printk("[%-5.5s%5u] " FMT "\n", \
29 : : current->comm, current->pid, ##__VA_ARGS__); \
30 : : } while (0)
31 : : #endif
32 : :
33 : : static struct kmem_cache *cred_jar;
34 : :
35 : : /* init to 2 - one for init_task, one to ensure it is never freed */
36 : : struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
37 : :
38 : : /*
39 : : * The initial credentials for the initial task
40 : : */
41 : : struct cred init_cred = {
42 : : .usage = ATOMIC_INIT(4),
43 : : #ifdef CONFIG_DEBUG_CREDENTIALS
44 : : .subscribers = ATOMIC_INIT(2),
45 : : .magic = CRED_MAGIC,
46 : : #endif
47 : : .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,
55 : : .securebits = SECUREBITS_DEFAULT,
56 : : .cap_inheritable = CAP_EMPTY_SET,
57 : : .cap_permitted = CAP_FULL_SET,
58 : : .cap_effective = CAP_FULL_SET,
59 : : .cap_bset = CAP_FULL_SET,
60 : : .user = INIT_USER,
61 : : .user_ns = &init_user_ns,
62 : : .group_info = &init_groups,
63 : : };
64 : :
65 : 108852 : static inline void set_cred_subscribers(struct cred *cred, int n)
66 : : {
67 : : #ifdef CONFIG_DEBUG_CREDENTIALS
68 : : atomic_set(&cred->subscribers, n);
69 : : #endif
70 : 108852 : }
71 : :
72 : : static inline int read_cred_subscribers(const struct cred *cred)
73 : : {
74 : : #ifdef CONFIG_DEBUG_CREDENTIALS
75 : : return atomic_read(&cred->subscribers);
76 : : #else
77 : : return 0;
78 : : #endif
79 : : }
80 : :
81 : 324833 : static inline void alter_cred_subscribers(const struct cred *_cred, int n)
82 : : {
83 : : #ifdef CONFIG_DEBUG_CREDENTIALS
84 : : struct cred *cred = (struct cred *) _cred;
85 : :
86 : : atomic_add(n, &cred->subscribers);
87 : : #endif
88 : 324833 : }
89 : :
90 : : /*
91 : : * The RCU callback to actually dispose of a set of credentials
92 : : */
93 : 106577 : static void put_cred_rcu(struct rcu_head *rcu)
94 : : {
95 : 106577 : struct cred *cred = container_of(rcu, struct cred, rcu);
96 : :
97 : 106577 : kdebug("put_cred_rcu(%p)", cred);
98 : :
99 : : #ifdef CONFIG_DEBUG_CREDENTIALS
100 : : if (cred->magic != CRED_MAGIC_DEAD ||
101 : : atomic_read(&cred->usage) != 0 ||
102 : : read_cred_subscribers(cred) != 0)
103 : : panic("CRED: put_cred_rcu() sees %p with"
104 : : " mag %x, put %p, usage %d, subscr %d\n",
105 : : cred, cred->magic, cred->put_addr,
106 : : atomic_read(&cred->usage),
107 : : read_cred_subscribers(cred));
108 : : #else
109 [ - + ]: 106577 : if (atomic_read(&cred->usage) != 0)
110 : 0 : panic("CRED: put_cred_rcu() sees %p with usage %d\n",
111 : : cred, atomic_read(&cred->usage));
112 : : #endif
113 : :
114 : 106577 : security_cred_free(cred);
115 : 106577 : key_put(cred->session_keyring);
116 : 106577 : key_put(cred->process_keyring);
117 : 106577 : key_put(cred->thread_keyring);
118 : 106577 : key_put(cred->request_key_auth);
119 [ + - ]: 106577 : if (cred->group_info)
120 [ + + ]: 106577 : put_group_info(cred->group_info);
121 : 106577 : free_uid(cred->user);
122 : 106577 : put_user_ns(cred->user_ns);
123 : 106577 : kmem_cache_free(cred_jar, cred);
124 : 106577 : }
125 : :
126 : : /**
127 : : * __put_cred - Destroy a set of credentials
128 : : * @cred: The record to release
129 : : *
130 : : * Destroy a set of credentials on which no references remain.
131 : : */
132 : 106766 : void __put_cred(struct cred *cred)
133 : : {
134 : 106766 : kdebug("__put_cred(%p{%d,%d})", cred,
135 : : atomic_read(&cred->usage),
136 : : read_cred_subscribers(cred));
137 : :
138 [ - + ]: 106766 : BUG_ON(atomic_read(&cred->usage) != 0);
139 : : #ifdef CONFIG_DEBUG_CREDENTIALS
140 : : BUG_ON(read_cred_subscribers(cred) != 0);
141 : : cred->magic = CRED_MAGIC_DEAD;
142 : : cred->put_addr = __builtin_return_address(0);
143 : : #endif
144 [ - + ]: 106766 : BUG_ON(cred == current->cred);
145 [ - + ]: 106766 : BUG_ON(cred == current->real_cred);
146 : :
147 [ + + ]: 106766 : if (cred->non_rcu)
148 : 66852 : put_cred_rcu(&cred->rcu);
149 : : else
150 : 39914 : call_rcu(&cred->rcu, put_cred_rcu);
151 : 106766 : }
152 : : EXPORT_SYMBOL(__put_cred);
153 : :
154 : : /*
155 : : * Clean up a task's credentials when it exits
156 : : */
157 : 10033 : void exit_creds(struct task_struct *tsk)
158 : : {
159 : 10033 : struct cred *cred;
160 : :
161 : 10033 : kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
162 : : atomic_read(&tsk->cred->usage),
163 : : read_cred_subscribers(tsk->cred));
164 : :
165 : 10033 : cred = (struct cred *) tsk->real_cred;
166 : 10033 : tsk->real_cred = NULL;
167 : 10033 : validate_creds(cred);
168 : 10033 : alter_cred_subscribers(cred, -1);
169 : 10033 : put_cred(cred);
170 : :
171 : 10033 : cred = (struct cred *) tsk->cred;
172 : 10033 : tsk->cred = NULL;
173 : 10033 : validate_creds(cred);
174 : 10033 : alter_cred_subscribers(cred, -1);
175 : 10033 : put_cred(cred);
176 : :
177 : : #ifdef CONFIG_KEYS_REQUEST_CACHE
178 : : key_put(tsk->cached_requested_key);
179 : : tsk->cached_requested_key = NULL;
180 : : #endif
181 : 10033 : }
182 : :
183 : : /**
184 : : * get_task_cred - Get another task's objective credentials
185 : : * @task: The task to query
186 : : *
187 : : * Get the objective credentials of a task, pinning them so that they can't go
188 : : * away. Accessing a task's credentials directly is not permitted.
189 : : *
190 : : * The caller must also make sure task doesn't get deleted, either by holding a
191 : : * ref on task or by holding tasklist_lock to prevent it from being unlinked.
192 : : */
193 : 3569 : const struct cred *get_task_cred(struct task_struct *task)
194 : : {
195 : 3569 : const struct cred *cred;
196 : :
197 : 3569 : rcu_read_lock();
198 : :
199 : 3569 : do {
200 [ - + ]: 3569 : cred = __task_cred((task));
201 [ - + ]: 3569 : BUG_ON(!cred);
202 [ - + ]: 3569 : } while (!get_cred_rcu(cred));
203 : :
204 : 3569 : rcu_read_unlock();
205 : 3569 : return cred;
206 : : }
207 : : EXPORT_SYMBOL(get_task_cred);
208 : :
209 : : /*
210 : : * Allocate blank credentials, such that the credentials can be filled in at a
211 : : * later date without risk of ENOMEM.
212 : : */
213 : 0 : struct cred *cred_alloc_blank(void)
214 : : {
215 : 0 : struct cred *new;
216 : :
217 : 0 : new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
218 [ # # ]: 0 : if (!new)
219 : : return NULL;
220 : :
221 : 0 : atomic_set(&new->usage, 1);
222 : : #ifdef CONFIG_DEBUG_CREDENTIALS
223 : : new->magic = CRED_MAGIC;
224 : : #endif
225 : :
226 [ # # ]: 0 : if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
227 : 0 : goto error;
228 : :
229 : : return new;
230 : :
231 : : error:
232 : 0 : abort_creds(new);
233 : 0 : return NULL;
234 : : }
235 : :
236 : : /**
237 : : * prepare_creds - Prepare a new set of credentials for modification
238 : : *
239 : : * Prepare a new set of task credentials for modification. A task's creds
240 : : * shouldn't generally be modified directly, therefore this function is used to
241 : : * prepare a new copy, which the caller then modifies and then commits by
242 : : * calling commit_creds().
243 : : *
244 : : * Preparation involves making a copy of the objective creds for modification.
245 : : *
246 : : * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
247 : : *
248 : : * Call commit_creds() or abort_creds() to clean up.
249 : : */
250 : 107508 : struct cred *prepare_creds(void)
251 : : {
252 : 107508 : struct task_struct *task = current;
253 : 107508 : const struct cred *old;
254 : 107508 : struct cred *new;
255 : :
256 : 107508 : validate_process_creds();
257 : :
258 : 107508 : new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
259 [ + - ]: 107508 : if (!new)
260 : : return NULL;
261 : :
262 : 107508 : kdebug("prepare_creds() alloc %p", new);
263 : :
264 : 107508 : old = task->cred;
265 : 107508 : memcpy(new, old, sizeof(struct cred));
266 : :
267 : 107508 : new->non_rcu = 0;
268 : 107508 : atomic_set(&new->usage, 1);
269 : 107508 : set_cred_subscribers(new, 0);
270 : 107508 : get_group_info(new->group_info);
271 : 107508 : get_uid(new->user);
272 [ + + ]: 107508 : get_user_ns(new->user_ns);
273 : :
274 : : #ifdef CONFIG_KEYS
275 [ + + ]: 107508 : key_get(new->session_keyring);
276 [ - + ]: 107508 : key_get(new->process_keyring);
277 [ - + ]: 107508 : key_get(new->thread_keyring);
278 [ - + ]: 107508 : key_get(new->request_key_auth);
279 : : #endif
280 : :
281 : : #ifdef CONFIG_SECURITY
282 : 107508 : new->security = NULL;
283 : : #endif
284 : :
285 [ - + ]: 107508 : if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
286 : 0 : goto error;
287 : : validate_creds(new);
288 : : return new;
289 : :
290 : : error:
291 : 0 : abort_creds(new);
292 : 0 : return NULL;
293 : : }
294 : : EXPORT_SYMBOL(prepare_creds);
295 : :
296 : : /*
297 : : * Prepare credentials for current to perform an execve()
298 : : * - The caller must hold ->cred_guard_mutex
299 : : */
300 : 26775 : struct cred *prepare_exec_creds(void)
301 : : {
302 : 26775 : struct cred *new;
303 : :
304 : 26775 : new = prepare_creds();
305 [ + - ]: 26775 : if (!new)
306 : : return new;
307 : :
308 : : #ifdef CONFIG_KEYS
309 : : /* newly exec'd tasks don't get a thread keyring */
310 : 26775 : key_put(new->thread_keyring);
311 : 26775 : new->thread_keyring = NULL;
312 : :
313 : : /* inherit the session keyring; new process keyring */
314 : 26775 : key_put(new->process_keyring);
315 : 26775 : new->process_keyring = NULL;
316 : : #endif
317 : :
318 : 26775 : return new;
319 : : }
320 : :
321 : : /*
322 : : * Copy credentials for the new process created by fork()
323 : : *
324 : : * We share if we can, but under some circumstances we have to generate a new
325 : : * set.
326 : : *
327 : : * The new process gets the current process's subjective credentials as its
328 : : * objective and subjective credentials
329 : : */
330 : 11613 : int copy_creds(struct task_struct *p, unsigned long clone_flags)
331 : : {
332 : 11613 : struct cred *new;
333 : 11613 : int ret;
334 : :
335 : : #ifdef CONFIG_KEYS_REQUEST_CACHE
336 : : p->cached_requested_key = NULL;
337 : : #endif
338 : :
339 : 11613 : if (
340 : : #ifdef CONFIG_KEYS
341 [ + - ]: 11613 : !p->cred->thread_keyring &&
342 : : #endif
343 [ + + ]: 11613 : clone_flags & CLONE_THREAD
344 : : ) {
345 [ + - ]: 84 : p->real_cred = get_cred(p->cred);
346 [ + - ]: 84 : get_cred(p->cred);
347 : 84 : alter_cred_subscribers(p->cred, 2);
348 : 84 : kdebug("share_creds(%p{%d,%d})",
349 : : p->cred, atomic_read(&p->cred->usage),
350 : : read_cred_subscribers(p->cred));
351 : 84 : atomic_inc(&p->cred->user->processes);
352 : 84 : return 0;
353 : : }
354 : :
355 : 11529 : new = prepare_creds();
356 [ + - ]: 11529 : if (!new)
357 : : return -ENOMEM;
358 : :
359 [ - + ]: 11529 : if (clone_flags & CLONE_NEWUSER) {
360 : 0 : ret = create_user_ns(new);
361 : 0 : if (ret < 0)
362 : 0 : goto error_put;
363 : : }
364 : :
365 : : #ifdef CONFIG_KEYS
366 : : /* new threads get their own thread keyrings if their parent already
367 : : * had one */
368 [ - + ]: 11529 : if (new->thread_keyring) {
369 : 0 : key_put(new->thread_keyring);
370 : 0 : new->thread_keyring = NULL;
371 [ # # ]: 0 : if (clone_flags & CLONE_THREAD)
372 : 0 : install_thread_keyring_to_cred(new);
373 : : }
374 : :
375 : : /* The process keyring is only shared between the threads in a process;
376 : : * anything outside of those threads doesn't inherit.
377 : : */
378 [ + - ]: 11529 : if (!(clone_flags & CLONE_THREAD)) {
379 : 11529 : key_put(new->process_keyring);
380 : 11529 : new->process_keyring = NULL;
381 : : }
382 : : #endif
383 : :
384 : 11529 : atomic_inc(&new->user->processes);
385 : 11529 : p->cred = p->real_cred = get_cred(new);
386 : 11529 : alter_cred_subscribers(new, 2);
387 : 11529 : validate_creds(new);
388 : 11529 : return 0;
389 : :
390 : : error_put:
391 : 0 : put_cred(new);
392 : 0 : return ret;
393 : : }
394 : :
395 : : static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
396 : : {
397 : : const struct user_namespace *set_ns = set->user_ns;
398 : : const struct user_namespace *subset_ns = subset->user_ns;
399 : :
400 : : /* If the two credentials are in the same user namespace see if
401 : : * the capabilities of subset are a subset of set.
402 : : */
403 : : if (set_ns == subset_ns)
404 : : return cap_issubset(subset->cap_permitted, set->cap_permitted);
405 : :
406 : : /* The credentials are in a different user namespaces
407 : : * therefore one is a subset of the other only if a set is an
408 : : * ancestor of subset and set->euid is owner of subset or one
409 : : * of subsets ancestors.
410 : : */
411 : : for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
412 : : if ((set_ns == subset_ns->parent) &&
413 : : uid_eq(subset_ns->owner, set->euid))
414 : : return true;
415 : : }
416 : :
417 : : return false;
418 : : }
419 : :
420 : : /**
421 : : * commit_creds - Install new credentials upon the current task
422 : : * @new: The credentials to be assigned
423 : : *
424 : : * Install a new set of credentials to the current task, using RCU to replace
425 : : * the old set. Both the objective and the subjective credentials pointers are
426 : : * updated. This function may not be called if the subjective credentials are
427 : : * in an overridden state.
428 : : *
429 : : * This function eats the caller's reference to the new credentials.
430 : : *
431 : : * Always returns 0 thus allowing this function to be tail-called at the end
432 : : * of, say, sys_setgid().
433 : : */
434 : 12873 : int commit_creds(struct cred *new)
435 : : {
436 [ - + ]: 12873 : struct task_struct *task = current;
437 : 12873 : const struct cred *old = task->real_cred;
438 : :
439 : 12873 : kdebug("commit_creds(%p{%d,%d})", new,
440 : : atomic_read(&new->usage),
441 : : read_cred_subscribers(new));
442 : :
443 [ - + ]: 12873 : BUG_ON(task->cred != old);
444 : : #ifdef CONFIG_DEBUG_CREDENTIALS
445 : : BUG_ON(read_cred_subscribers(old) < 2);
446 : : validate_creds(old);
447 : : validate_creds(new);
448 : : #endif
449 [ - + ]: 12873 : BUG_ON(atomic_read(&new->usage) < 1);
450 : :
451 [ + - ]: 12873 : get_cred(new); /* we will require a ref for the subj creds too */
452 : :
453 : : /* dumpability changes */
454 [ + + + + ]: 12873 : if (!uid_eq(old->euid, new->euid) ||
455 [ + - ]: 12747 : !gid_eq(old->egid, new->egid) ||
456 [ + - ]: 12747 : !uid_eq(old->fsuid, new->fsuid) ||
457 [ - + ]: 12747 : !gid_eq(old->fsgid, new->fsgid) ||
458 : 12747 : !cred_cap_issubset(old, new)) {
459 [ + - ]: 126 : if (task->mm)
460 : 126 : set_dumpable(task->mm, suid_dumpable);
461 : 126 : task->pdeath_signal = 0;
462 : : /*
463 : : * If a task drops privileges and becomes nondumpable,
464 : : * the dumpability change must become visible before
465 : : * the credential change; otherwise, a __ptrace_may_access()
466 : : * racing with this change may be able to attach to a task it
467 : : * shouldn't be able to attach to (as if the task had dropped
468 : : * privileges without becoming nondumpable).
469 : : * Pairs with a read barrier in __ptrace_may_access().
470 : : */
471 : 126 : smp_wmb();
472 : : }
473 : :
474 : : /* alter the thread keyring */
475 [ + + ]: 12873 : if (!uid_eq(new->fsuid, old->fsuid))
476 : 63 : key_fsuid_changed(new);
477 [ + + ]: 12873 : if (!gid_eq(new->fsgid, old->fsgid))
478 : 63 : key_fsgid_changed(new);
479 : :
480 : : /* do it
481 : : * RLIMIT_NPROC limits on user->processes have already been checked
482 : : * in set_user().
483 : : */
484 : 12873 : alter_cred_subscribers(new, 2);
485 [ + + ]: 12873 : if (new->user != old->user)
486 : 63 : atomic_inc(&new->user->processes);
487 : 12873 : rcu_assign_pointer(task->real_cred, new);
488 [ + + ]: 12873 : rcu_assign_pointer(task->cred, new);
489 [ + + ]: 12873 : if (new->user != old->user)
490 : 63 : atomic_dec(&old->user->processes);
491 : 12873 : alter_cred_subscribers(old, -2);
492 : :
493 : : /* send notifications */
494 [ + + + + ]: 12873 : if (!uid_eq(new->uid, old->uid) ||
495 [ + - ]: 12768 : !uid_eq(new->euid, old->euid) ||
496 [ - + ]: 12768 : !uid_eq(new->suid, old->suid) ||
497 : : !uid_eq(new->fsuid, old->fsuid))
498 : 105 : proc_id_connector(task, PROC_EVENT_UID);
499 : :
500 [ + + + + ]: 12873 : if (!gid_eq(new->gid, old->gid) ||
501 [ + - ]: 12768 : !gid_eq(new->egid, old->egid) ||
502 [ - + ]: 12768 : !gid_eq(new->sgid, old->sgid) ||
503 : : !gid_eq(new->fsgid, old->fsgid))
504 : 105 : proc_id_connector(task, PROC_EVENT_GID);
505 : :
506 : : /* release the old obj and subj refs both */
507 : 12873 : put_cred(old);
508 : 12873 : put_cred(old);
509 : 12873 : return 0;
510 : : }
511 : : EXPORT_SYMBOL(commit_creds);
512 : :
513 : : /**
514 : : * abort_creds - Discard a set of credentials and unlock the current task
515 : : * @new: The credentials that were going to be applied
516 : : *
517 : : * Discard a set of credentials that were under construction and unlock the
518 : : * current task.
519 : : */
520 : 17556 : void abort_creds(struct cred *new)
521 : : {
522 : 17556 : kdebug("abort_creds(%p{%d,%d})", new,
523 : : atomic_read(&new->usage),
524 : : read_cred_subscribers(new));
525 : :
526 : : #ifdef CONFIG_DEBUG_CREDENTIALS
527 : : BUG_ON(read_cred_subscribers(new) != 0);
528 : : #endif
529 [ - + ]: 17556 : BUG_ON(atomic_read(&new->usage) < 1);
530 : 17556 : put_cred(new);
531 : 17556 : }
532 : : EXPORT_SYMBOL(abort_creds);
533 : :
534 : : /**
535 : : * override_creds - Override the current process's subjective credentials
536 : : * @new: The credentials to be assigned
537 : : *
538 : : * Install a set of temporary override subjective credentials on the current
539 : : * process, returning the old set for later reversion.
540 : : */
541 : 66852 : const struct cred *override_creds(const struct cred *new)
542 : : {
543 : 66852 : const struct cred *old = current->cred;
544 : :
545 : 66852 : kdebug("override_creds(%p{%d,%d})", new,
546 : : atomic_read(&new->usage),
547 : : read_cred_subscribers(new));
548 : :
549 : 66852 : validate_creds(old);
550 : 66852 : validate_creds(new);
551 : :
552 : : /*
553 : : * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
554 : : *
555 : : * That means that we do not clear the 'non_rcu' flag, since
556 : : * we are only installing the cred into the thread-synchronous
557 : : * '->cred' pointer, not the '->real_cred' pointer that is
558 : : * visible to other threads under RCU.
559 : : *
560 : : * Also note that we did validate_creds() manually, not depending
561 : : * on the validation in 'get_cred()'.
562 : : */
563 : 66852 : get_new_cred((struct cred *)new);
564 : 66852 : alter_cred_subscribers(new, 1);
565 : 66852 : rcu_assign_pointer(current->cred, new);
566 : 66852 : alter_cred_subscribers(old, -1);
567 : :
568 : 66852 : kdebug("override_creds() = %p{%d,%d}", old,
569 : : atomic_read(&old->usage),
570 : : read_cred_subscribers(old));
571 : 66852 : return old;
572 : : }
573 : : EXPORT_SYMBOL(override_creds);
574 : :
575 : : /**
576 : : * revert_creds - Revert a temporary subjective credentials override
577 : : * @old: The credentials to be restored
578 : : *
579 : : * Revert a temporary set of override subjective credentials to an old set,
580 : : * discarding the override set.
581 : : */
582 : 66852 : void revert_creds(const struct cred *old)
583 : : {
584 : 66852 : const struct cred *override = current->cred;
585 : :
586 : 66852 : kdebug("revert_creds(%p{%d,%d})", old,
587 : : atomic_read(&old->usage),
588 : : read_cred_subscribers(old));
589 : :
590 : 66852 : validate_creds(old);
591 : 66852 : validate_creds(override);
592 : 66852 : alter_cred_subscribers(old, 1);
593 : 66852 : rcu_assign_pointer(current->cred, old);
594 : 66852 : alter_cred_subscribers(override, -1);
595 : 66852 : put_cred(override);
596 : 66852 : }
597 : : EXPORT_SYMBOL(revert_creds);
598 : :
599 : : /**
600 : : * cred_fscmp - Compare two credentials with respect to filesystem access.
601 : : * @a: The first credential
602 : : * @b: The second credential
603 : : *
604 : : * cred_cmp() will return zero if both credentials have the same
605 : : * fsuid, fsgid, and supplementary groups. That is, if they will both
606 : : * provide the same access to files based on mode/uid/gid.
607 : : * If the credentials are different, then either -1 or 1 will
608 : : * be returned depending on whether @a comes before or after @b
609 : : * respectively in an arbitrary, but stable, ordering of credentials.
610 : : *
611 : : * Return: -1, 0, or 1 depending on comparison
612 : : */
613 : 0 : int cred_fscmp(const struct cred *a, const struct cred *b)
614 : : {
615 : 0 : struct group_info *ga, *gb;
616 : 0 : int g;
617 : :
618 [ # # ]: 0 : if (a == b)
619 : : return 0;
620 [ # # ]: 0 : if (uid_lt(a->fsuid, b->fsuid))
621 : : return -1;
622 [ # # ]: 0 : if (uid_gt(a->fsuid, b->fsuid))
623 : : return 1;
624 : :
625 [ # # ]: 0 : if (gid_lt(a->fsgid, b->fsgid))
626 : : return -1;
627 [ # # ]: 0 : if (gid_gt(a->fsgid, b->fsgid))
628 : : return 1;
629 : :
630 : 0 : ga = a->group_info;
631 : 0 : gb = b->group_info;
632 [ # # ]: 0 : if (ga == gb)
633 : : return 0;
634 [ # # ]: 0 : if (ga == NULL)
635 : : return -1;
636 [ # # ]: 0 : if (gb == NULL)
637 : : return 1;
638 [ # # ]: 0 : if (ga->ngroups < gb->ngroups)
639 : : return -1;
640 [ # # ]: 0 : if (ga->ngroups > gb->ngroups)
641 : : return 1;
642 : :
643 [ # # ]: 0 : for (g = 0; g < ga->ngroups; g++) {
644 [ # # ]: 0 : if (gid_lt(ga->gid[g], gb->gid[g]))
645 : : return -1;
646 [ # # ]: 0 : if (gid_gt(ga->gid[g], gb->gid[g]))
647 : : return 1;
648 : : }
649 : : return 0;
650 : : }
651 : : EXPORT_SYMBOL(cred_fscmp);
652 : :
653 : : /*
654 : : * initialise the credentials stuff
655 : : */
656 : 21 : void __init cred_init(void)
657 : : {
658 : : /* allocate a slab in which we can store credentials */
659 : 21 : cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
660 : : SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
661 : 21 : }
662 : :
663 : : /**
664 : : * prepare_kernel_cred - Prepare a set of credentials for a kernel service
665 : : * @daemon: A userspace daemon to be used as a reference
666 : : *
667 : : * Prepare a set of credentials for a kernel service. This can then be used to
668 : : * override a task's own credentials so that work can be done on behalf of that
669 : : * task that requires a different subjective context.
670 : : *
671 : : * @daemon is used to provide a base for the security record, but can be NULL.
672 : : * If @daemon is supplied, then the security data will be derived from that;
673 : : * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
674 : : *
675 : : * The caller may change these controls afterwards if desired.
676 : : *
677 : : * Returns the new credentials or NULL if out of memory.
678 : : *
679 : : * Does not take, and does not return holding current->cred_replace_mutex.
680 : : */
681 : 1344 : struct cred *prepare_kernel_cred(struct task_struct *daemon)
682 : : {
683 : 1344 : const struct cred *old;
684 : 1344 : struct cred *new;
685 : :
686 : 1344 : new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
687 [ + - ]: 1344 : if (!new)
688 : : return NULL;
689 : :
690 : 1344 : kdebug("prepare_kernel_cred() alloc %p", new);
691 : :
692 [ + + ]: 1344 : if (daemon)
693 : 1302 : old = get_task_cred(daemon);
694 : : else
695 : 42 : old = get_cred(&init_cred);
696 : :
697 : 1344 : validate_creds(old);
698 : :
699 : 1344 : *new = *old;
700 : 1344 : new->non_rcu = 0;
701 : 1344 : atomic_set(&new->usage, 1);
702 : 1344 : set_cred_subscribers(new, 0);
703 : 1344 : get_uid(new->user);
704 : 1344 : get_user_ns(new->user_ns);
705 : 1344 : get_group_info(new->group_info);
706 : :
707 : : #ifdef CONFIG_KEYS
708 : 1344 : new->session_keyring = NULL;
709 : 1344 : new->process_keyring = NULL;
710 : 1344 : new->thread_keyring = NULL;
711 : 1344 : new->request_key_auth = NULL;
712 : 1344 : new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
713 : : #endif
714 : :
715 : : #ifdef CONFIG_SECURITY
716 : 1344 : new->security = NULL;
717 : : #endif
718 [ - + ]: 1344 : if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
719 : 0 : goto error;
720 : :
721 : 1344 : put_cred(old);
722 : 1344 : validate_creds(new);
723 : 1344 : return new;
724 : :
725 : : error:
726 : 0 : put_cred(new);
727 : 0 : put_cred(old);
728 : 0 : return NULL;
729 : : }
730 : : EXPORT_SYMBOL(prepare_kernel_cred);
731 : :
732 : : /**
733 : : * set_security_override - Set the security ID in a set of credentials
734 : : * @new: The credentials to alter
735 : : * @secid: The LSM security ID to set
736 : : *
737 : : * Set the LSM security ID in a set of credentials so that the subjective
738 : : * security is overridden when an alternative set of credentials is used.
739 : : */
740 : 0 : int set_security_override(struct cred *new, u32 secid)
741 : : {
742 : 0 : return security_kernel_act_as(new, secid);
743 : : }
744 : : EXPORT_SYMBOL(set_security_override);
745 : :
746 : : /**
747 : : * set_security_override_from_ctx - Set the security ID in a set of credentials
748 : : * @new: The credentials to alter
749 : : * @secctx: The LSM security context to generate the security ID from.
750 : : *
751 : : * Set the LSM security ID in a set of credentials so that the subjective
752 : : * security is overridden when an alternative set of credentials is used. The
753 : : * security ID is specified in string form as a security context to be
754 : : * interpreted by the LSM.
755 : : */
756 : 0 : int set_security_override_from_ctx(struct cred *new, const char *secctx)
757 : : {
758 : 0 : u32 secid;
759 : 0 : int ret;
760 : :
761 : 0 : ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
762 [ # # ]: 0 : if (ret < 0)
763 : : return ret;
764 : :
765 : 0 : return set_security_override(new, secid);
766 : : }
767 : : EXPORT_SYMBOL(set_security_override_from_ctx);
768 : :
769 : : /**
770 : : * set_create_files_as - Set the LSM file create context in a set of credentials
771 : : * @new: The credentials to alter
772 : : * @inode: The inode to take the context from
773 : : *
774 : : * Change the LSM file creation context in a set of credentials to be the same
775 : : * as the object context of the specified inode, so that the new inodes have
776 : : * the same MAC context as that inode.
777 : : */
778 : 0 : int set_create_files_as(struct cred *new, struct inode *inode)
779 : : {
780 [ # # # # ]: 0 : if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
781 : : return -EINVAL;
782 : 0 : new->fsuid = inode->i_uid;
783 : 0 : new->fsgid = inode->i_gid;
784 : 0 : return security_kernel_create_files_as(new, inode);
785 : : }
786 : : EXPORT_SYMBOL(set_create_files_as);
787 : :
788 : : #ifdef CONFIG_DEBUG_CREDENTIALS
789 : :
790 : : bool creds_are_invalid(const struct cred *cred)
791 : : {
792 : : if (cred->magic != CRED_MAGIC)
793 : : return true;
794 : : return false;
795 : : }
796 : : EXPORT_SYMBOL(creds_are_invalid);
797 : :
798 : : /*
799 : : * dump invalid credentials
800 : : */
801 : : static void dump_invalid_creds(const struct cred *cred, const char *label,
802 : : const struct task_struct *tsk)
803 : : {
804 : : printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
805 : : label, cred,
806 : : cred == &init_cred ? "[init]" : "",
807 : : cred == tsk->real_cred ? "[real]" : "",
808 : : cred == tsk->cred ? "[eff]" : "");
809 : : printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
810 : : cred->magic, cred->put_addr);
811 : : printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
812 : : atomic_read(&cred->usage),
813 : : read_cred_subscribers(cred));
814 : : printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
815 : : from_kuid_munged(&init_user_ns, cred->uid),
816 : : from_kuid_munged(&init_user_ns, cred->euid),
817 : : from_kuid_munged(&init_user_ns, cred->suid),
818 : : from_kuid_munged(&init_user_ns, cred->fsuid));
819 : : printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
820 : : from_kgid_munged(&init_user_ns, cred->gid),
821 : : from_kgid_munged(&init_user_ns, cred->egid),
822 : : from_kgid_munged(&init_user_ns, cred->sgid),
823 : : from_kgid_munged(&init_user_ns, cred->fsgid));
824 : : #ifdef CONFIG_SECURITY
825 : : printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
826 : : if ((unsigned long) cred->security >= PAGE_SIZE &&
827 : : (((unsigned long) cred->security & 0xffffff00) !=
828 : : (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
829 : : printk(KERN_ERR "CRED: ->security {%x, %x}\n",
830 : : ((u32*)cred->security)[0],
831 : : ((u32*)cred->security)[1]);
832 : : #endif
833 : : }
834 : :
835 : : /*
836 : : * report use of invalid credentials
837 : : */
838 : : void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
839 : : {
840 : : printk(KERN_ERR "CRED: Invalid credentials\n");
841 : : printk(KERN_ERR "CRED: At %s:%u\n", file, line);
842 : : dump_invalid_creds(cred, "Specified", current);
843 : : BUG();
844 : : }
845 : : EXPORT_SYMBOL(__invalid_creds);
846 : :
847 : : /*
848 : : * check the credentials on a process
849 : : */
850 : : void __validate_process_creds(struct task_struct *tsk,
851 : : const char *file, unsigned line)
852 : : {
853 : : if (tsk->cred == tsk->real_cred) {
854 : : if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
855 : : creds_are_invalid(tsk->cred)))
856 : : goto invalid_creds;
857 : : } else {
858 : : if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
859 : : read_cred_subscribers(tsk->cred) < 1 ||
860 : : creds_are_invalid(tsk->real_cred) ||
861 : : creds_are_invalid(tsk->cred)))
862 : : goto invalid_creds;
863 : : }
864 : : return;
865 : :
866 : : invalid_creds:
867 : : printk(KERN_ERR "CRED: Invalid process credentials\n");
868 : : printk(KERN_ERR "CRED: At %s:%u\n", file, line);
869 : :
870 : : dump_invalid_creds(tsk->real_cred, "Real", tsk);
871 : : if (tsk->cred != tsk->real_cred)
872 : : dump_invalid_creds(tsk->cred, "Effective", tsk);
873 : : else
874 : : printk(KERN_ERR "CRED: Effective creds == Real creds\n");
875 : : BUG();
876 : : }
877 : : EXPORT_SYMBOL(__validate_process_creds);
878 : :
879 : : /*
880 : : * check creds for do_exit()
881 : : */
882 : : void validate_creds_for_do_exit(struct task_struct *tsk)
883 : : {
884 : : kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
885 : : tsk->real_cred, tsk->cred,
886 : : atomic_read(&tsk->cred->usage),
887 : : read_cred_subscribers(tsk->cred));
888 : :
889 : : __validate_process_creds(tsk, __FILE__, __LINE__);
890 : : }
891 : :
892 : : #endif /* CONFIG_DEBUG_CREDENTIALS */
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