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 | |
8 | #define pr_fmt(fmt) "CRED: " fmt |
9 | |
10 | #include <linux/export.h> |
11 | #include <linux/cred.h> |
12 | #include <linux/slab.h> |
13 | #include <linux/sched.h> |
14 | #include <linux/sched/coredump.h> |
15 | #include <linux/key.h> |
16 | #include <linux/keyctl.h> |
17 | #include <linux/init_task.h> |
18 | #include <linux/security.h> |
19 | #include <linux/binfmts.h> |
20 | #include <linux/cn_proc.h> |
21 | #include <linux/uidgid.h> |
22 | |
23 | #if 0 |
24 | #define kdebug(FMT, ...) \ |
25 | printk("[%-5.5s%5u] " FMT "\n", \ |
26 | current->comm, current->pid, ##__VA_ARGS__) |
27 | #else |
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) |
34 | #endif |
35 | |
36 | static struct kmem_cache *cred_jar; |
37 | |
38 | /* init to 2 - one for init_task, one to ensure it is never freed */ |
39 | static struct group_info init_groups = { .usage = REFCOUNT_INIT(2) }; |
40 | |
41 | /* |
42 | * The initial credentials for the initial task |
43 | */ |
44 | struct cred init_cred = { |
45 | .usage = ATOMIC_INIT(4), |
46 | #ifdef CONFIG_DEBUG_CREDENTIALS |
47 | .subscribers = ATOMIC_INIT(2), |
48 | .magic = CRED_MAGIC, |
49 | #endif |
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, |
58 | .securebits = SECUREBITS_DEFAULT, |
59 | .cap_inheritable = CAP_EMPTY_SET, |
60 | .cap_permitted = CAP_FULL_SET, |
61 | .cap_effective = CAP_FULL_SET, |
62 | .cap_bset = CAP_FULL_SET, |
63 | .user = INIT_USER, |
64 | .user_ns = &init_user_ns, |
65 | .group_info = &init_groups, |
66 | .ucounts = &init_ucounts, |
67 | }; |
68 | |
69 | static inline void set_cred_subscribers(struct cred *cred, int n) |
70 | { |
71 | #ifdef CONFIG_DEBUG_CREDENTIALS |
72 | atomic_set(v: &cred->subscribers, i: 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(v: &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(i: n, v: &cred->subscribers); |
91 | #endif |
92 | } |
93 | |
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 | |
101 | kdebug("put_cred_rcu(%p)" , cred); |
102 | |
103 | #ifdef CONFIG_DEBUG_CREDENTIALS |
104 | if (cred->magic != CRED_MAGIC_DEAD || |
105 | atomic_read(v: &cred->usage) != 0 || |
106 | read_cred_subscribers(cred) != 0) |
107 | panic(fmt: "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(v: &cred->usage), |
111 | read_cred_subscribers(cred)); |
112 | #else |
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)); |
116 | #endif |
117 | |
118 | security_cred_free(cred); |
119 | key_put(key: cred->session_keyring); |
120 | key_put(key: cred->process_keyring); |
121 | key_put(key: cred->thread_keyring); |
122 | key_put(key: cred->request_key_auth); |
123 | if (cred->group_info) |
124 | put_group_info(cred->group_info); |
125 | free_uid(cred->user); |
126 | if (cred->ucounts) |
127 | put_ucounts(ucounts: cred->ucounts); |
128 | put_user_ns(ns: cred->user_ns); |
129 | kmem_cache_free(s: cred_jar, objp: cred); |
130 | } |
131 | |
132 | /** |
133 | * __put_cred - Destroy a set of credentials |
134 | * @cred: The record to release |
135 | * |
136 | * Destroy a set of credentials on which no references remain. |
137 | */ |
138 | void __put_cred(struct cred *cred) |
139 | { |
140 | kdebug("__put_cred(%p{%d,%d})" , cred, |
141 | atomic_read(&cred->usage), |
142 | read_cred_subscribers(cred)); |
143 | |
144 | BUG_ON(atomic_read(&cred->usage) != 0); |
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); |
152 | |
153 | if (cred->non_rcu) |
154 | put_cred_rcu(rcu: &cred->rcu); |
155 | else |
156 | call_rcu(head: &cred->rcu, func: put_cred_rcu); |
157 | } |
158 | EXPORT_SYMBOL(__put_cred); |
159 | |
160 | /* |
161 | * Clean up a task's credentials when it exits |
162 | */ |
163 | void exit_creds(struct task_struct *tsk) |
164 | { |
165 | struct cred *real_cred, *cred; |
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 | |
171 | real_cred = (struct cred *) tsk->real_cred; |
172 | tsk->real_cred = NULL; |
173 | |
174 | cred = (struct cred *) tsk->cred; |
175 | tsk->cred = NULL; |
176 | |
177 | validate_creds(cred); |
178 | if (real_cred == cred) { |
179 | alter_cred_subscribers(cred: cred, n: -2); |
180 | put_cred_many(cred: cred, nr: 2); |
181 | } else { |
182 | validate_creds(real_cred); |
183 | alter_cred_subscribers(cred: real_cred, n: -1); |
184 | put_cred(cred: real_cred); |
185 | alter_cred_subscribers(cred: cred, n: -1); |
186 | put_cred(cred); |
187 | } |
188 | |
189 | #ifdef CONFIG_KEYS_REQUEST_CACHE |
190 | key_put(key: tsk->cached_requested_key); |
191 | tsk->cached_requested_key = NULL; |
192 | #endif |
193 | } |
194 | |
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); |
214 | } while (!get_cred_rcu(cred)); |
215 | |
216 | rcu_read_unlock(); |
217 | return cred; |
218 | } |
219 | EXPORT_SYMBOL(get_task_cred); |
220 | |
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(k: cred_jar, GFP_KERNEL); |
230 | if (!new) |
231 | return NULL; |
232 | |
233 | atomic_set(v: &new->usage, i: 1); |
234 | #ifdef CONFIG_DEBUG_CREDENTIALS |
235 | new->magic = CRED_MAGIC; |
236 | #endif |
237 | if (security_cred_alloc_blank(cred: new, GFP_KERNEL_ACCOUNT) < 0) |
238 | goto error; |
239 | |
240 | return new; |
241 | |
242 | error: |
243 | abort_creds(new); |
244 | return NULL; |
245 | } |
246 | |
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 | * |
255 | * Preparation involves making a copy of the objective creds for modification. |
256 | * |
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 | |
267 | validate_process_creds(); |
268 | |
269 | new = kmem_cache_alloc(cachep: cred_jar, GFP_KERNEL); |
270 | if (!new) |
271 | return NULL; |
272 | |
273 | kdebug("prepare_creds() alloc %p" , new); |
274 | |
275 | old = task->cred; |
276 | memcpy(new, old, sizeof(struct cred)); |
277 | |
278 | new->non_rcu = 0; |
279 | atomic_set(v: &new->usage, i: 1); |
280 | set_cred_subscribers(cred: new, n: 0); |
281 | get_group_info(gi: new->group_info); |
282 | get_uid(u: new->user); |
283 | get_user_ns(ns: new->user_ns); |
284 | |
285 | #ifdef CONFIG_KEYS |
286 | key_get(key: new->session_keyring); |
287 | key_get(key: new->process_keyring); |
288 | key_get(key: new->thread_keyring); |
289 | key_get(key: new->request_key_auth); |
290 | #endif |
291 | |
292 | #ifdef CONFIG_SECURITY |
293 | new->security = NULL; |
294 | #endif |
295 | |
296 | new->ucounts = get_ucounts(ucounts: new->ucounts); |
297 | if (!new->ucounts) |
298 | goto error; |
299 | |
300 | if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) |
301 | goto error; |
302 | |
303 | validate_creds(new); |
304 | return new; |
305 | |
306 | error: |
307 | abort_creds(new); |
308 | return NULL; |
309 | } |
310 | EXPORT_SYMBOL(prepare_creds); |
311 | |
312 | /* |
313 | * Prepare credentials for current to perform an execve() |
314 | * - The caller must hold ->cred_guard_mutex |
315 | */ |
316 | struct cred *prepare_exec_creds(void) |
317 | { |
318 | struct cred *new; |
319 | |
320 | new = prepare_creds(); |
321 | if (!new) |
322 | return new; |
323 | |
324 | #ifdef CONFIG_KEYS |
325 | /* newly exec'd tasks don't get a thread keyring */ |
326 | key_put(key: new->thread_keyring); |
327 | new->thread_keyring = NULL; |
328 | |
329 | /* inherit the session keyring; new process keyring */ |
330 | key_put(key: new->process_keyring); |
331 | new->process_keyring = NULL; |
332 | #endif |
333 | |
334 | new->suid = new->fsuid = new->euid; |
335 | new->sgid = new->fsgid = new->egid; |
336 | |
337 | return new; |
338 | } |
339 | |
340 | /* |
341 | * Copy credentials for the new process created by fork() |
342 | * |
343 | * We share if we can, but under some circumstances we have to generate a new |
344 | * set. |
345 | * |
346 | * The new process gets the current process's subjective credentials as its |
347 | * objective and subjective credentials |
348 | */ |
349 | int copy_creds(struct task_struct *p, unsigned long clone_flags) |
350 | { |
351 | struct cred *new; |
352 | int ret; |
353 | |
354 | #ifdef CONFIG_KEYS_REQUEST_CACHE |
355 | p->cached_requested_key = NULL; |
356 | #endif |
357 | |
358 | if ( |
359 | #ifdef CONFIG_KEYS |
360 | !p->cred->thread_keyring && |
361 | #endif |
362 | clone_flags & CLONE_THREAD |
363 | ) { |
364 | p->real_cred = get_cred_many(cred: p->cred, nr: 2); |
365 | alter_cred_subscribers(cred: p->cred, n: 2); |
366 | kdebug("share_creds(%p{%d,%d})" , |
367 | p->cred, atomic_read(&p->cred->usage), |
368 | read_cred_subscribers(p->cred)); |
369 | inc_rlimit_ucounts(task_ucounts(p), type: UCOUNT_RLIMIT_NPROC, v: 1); |
370 | return 0; |
371 | } |
372 | |
373 | new = prepare_creds(); |
374 | if (!new) |
375 | return -ENOMEM; |
376 | |
377 | if (clone_flags & CLONE_NEWUSER) { |
378 | ret = create_user_ns(new); |
379 | if (ret < 0) |
380 | goto error_put; |
381 | ret = set_cred_ucounts(new); |
382 | if (ret < 0) |
383 | goto error_put; |
384 | } |
385 | |
386 | #ifdef CONFIG_KEYS |
387 | /* new threads get their own thread keyrings if their parent already |
388 | * had one */ |
389 | if (new->thread_keyring) { |
390 | key_put(key: new->thread_keyring); |
391 | new->thread_keyring = NULL; |
392 | if (clone_flags & CLONE_THREAD) |
393 | install_thread_keyring_to_cred(cred: new); |
394 | } |
395 | |
396 | /* The process keyring is only shared between the threads in a process; |
397 | * anything outside of those threads doesn't inherit. |
398 | */ |
399 | if (!(clone_flags & CLONE_THREAD)) { |
400 | key_put(key: new->process_keyring); |
401 | new->process_keyring = NULL; |
402 | } |
403 | #endif |
404 | |
405 | p->cred = p->real_cred = get_cred(cred: new); |
406 | inc_rlimit_ucounts(task_ucounts(p), type: UCOUNT_RLIMIT_NPROC, v: 1); |
407 | alter_cred_subscribers(cred: new, n: 2); |
408 | validate_creds(new); |
409 | return 0; |
410 | |
411 | error_put: |
412 | put_cred(cred: new); |
413 | return ret; |
414 | } |
415 | |
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(a: subset->cap_permitted, set: 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(left: subset_ns->owner, right: set->euid)) |
435 | return true; |
436 | } |
437 | |
438 | return false; |
439 | } |
440 | |
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 |
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. |
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; |
458 | const struct cred *old = task->real_cred; |
459 | |
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 |
470 | BUG_ON(atomic_read(&new->usage) < 1); |
471 | |
472 | get_cred(cred: new); /* we will require a ref for the subj creds too */ |
473 | |
474 | /* dumpability changes */ |
475 | if (!uid_eq(left: old->euid, right: new->euid) || |
476 | !gid_eq(left: old->egid, right: new->egid) || |
477 | !uid_eq(left: old->fsuid, right: new->fsuid) || |
478 | !gid_eq(left: old->fsgid, right: new->fsgid) || |
479 | !cred_cap_issubset(set: old, subset: new)) { |
480 | if (task->mm) |
481 | set_dumpable(mm: task->mm, value: suid_dumpable); |
482 | task->pdeath_signal = 0; |
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 | */ |
492 | smp_wmb(); |
493 | } |
494 | |
495 | /* alter the thread keyring */ |
496 | if (!uid_eq(left: new->fsuid, right: old->fsuid)) |
497 | key_fsuid_changed(new_cred: new); |
498 | if (!gid_eq(left: new->fsgid, right: old->fsgid)) |
499 | key_fsgid_changed(new_cred: new); |
500 | |
501 | /* do it |
502 | * RLIMIT_NPROC limits on user->processes have already been checked |
503 | * in set_user(). |
504 | */ |
505 | alter_cred_subscribers(cred: new, n: 2); |
506 | if (new->user != old->user || new->user_ns != old->user_ns) |
507 | inc_rlimit_ucounts(ucounts: new->ucounts, type: UCOUNT_RLIMIT_NPROC, v: 1); |
508 | rcu_assign_pointer(task->real_cred, new); |
509 | rcu_assign_pointer(task->cred, new); |
510 | if (new->user != old->user || new->user_ns != old->user_ns) |
511 | dec_rlimit_ucounts(ucounts: old->ucounts, type: UCOUNT_RLIMIT_NPROC, v: 1); |
512 | alter_cred_subscribers(cred: old, n: -2); |
513 | |
514 | /* send notifications */ |
515 | if (!uid_eq(left: new->uid, right: old->uid) || |
516 | !uid_eq(left: new->euid, right: old->euid) || |
517 | !uid_eq(left: new->suid, right: old->suid) || |
518 | !uid_eq(left: new->fsuid, right: old->fsuid)) |
519 | proc_id_connector(task, which_id: PROC_EVENT_UID); |
520 | |
521 | if (!gid_eq(left: new->gid, right: old->gid) || |
522 | !gid_eq(left: new->egid, right: old->egid) || |
523 | !gid_eq(left: new->sgid, right: old->sgid) || |
524 | !gid_eq(left: new->fsgid, right: old->fsgid)) |
525 | proc_id_connector(task, which_id: PROC_EVENT_GID); |
526 | |
527 | /* release the old obj and subj refs both */ |
528 | put_cred_many(cred: old, nr: 2); |
529 | return 0; |
530 | } |
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 | { |
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 |
549 | BUG_ON(atomic_read(&new->usage) < 1); |
550 | put_cred(cred: new); |
551 | } |
552 | EXPORT_SYMBOL(abort_creds); |
553 | |
554 | /** |
555 | * override_creds - Override the current process's subjective credentials |
556 | * @new: The credentials to be assigned |
557 | * |
558 | * Install a set of temporary override subjective credentials on the current |
559 | * process, returning the old set for later reversion. |
560 | */ |
561 | const struct cred *override_creds(const struct cred *new) |
562 | { |
563 | const struct cred *old = current->cred; |
564 | |
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); |
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(cred: (struct cred *)new); |
584 | alter_cred_subscribers(cred: new, n: 1); |
585 | rcu_assign_pointer(current->cred, new); |
586 | alter_cred_subscribers(cred: old, n: -1); |
587 | |
588 | kdebug("override_creds() = %p{%d,%d}" , old, |
589 | atomic_read(&old->usage), |
590 | read_cred_subscribers(old)); |
591 | return old; |
592 | } |
593 | EXPORT_SYMBOL(override_creds); |
594 | |
595 | /** |
596 | * revert_creds - Revert a temporary subjective credentials override |
597 | * @old: The credentials to be restored |
598 | * |
599 | * Revert a temporary set of override subjective credentials to an old set, |
600 | * discarding the override set. |
601 | */ |
602 | void revert_creds(const struct cred *old) |
603 | { |
604 | const struct cred *override = current->cred; |
605 | |
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(cred: old, n: 1); |
613 | rcu_assign_pointer(current->cred, old); |
614 | alter_cred_subscribers(cred: override, n: -1); |
615 | put_cred(cred: override); |
616 | } |
617 | EXPORT_SYMBOL(revert_creds); |
618 | |
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(left: a->fsuid, right: b->fsuid)) |
641 | return -1; |
642 | if (uid_gt(left: a->fsuid, right: b->fsuid)) |
643 | return 1; |
644 | |
645 | if (gid_lt(left: a->fsgid, right: b->fsgid)) |
646 | return -1; |
647 | if (gid_gt(left: a->fsgid, right: 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(left: ga->gid[g], right: gb->gid[g])) |
665 | return -1; |
666 | if (gid_gt(left: ga->gid[g], right: gb->gid[g])) |
667 | return 1; |
668 | } |
669 | return 0; |
670 | } |
671 | EXPORT_SYMBOL(cred_fscmp); |
672 | |
673 | int set_cred_ucounts(struct cred *new) |
674 | { |
675 | struct ucounts *new_ucounts, *old_ucounts = new->ucounts; |
676 | |
677 | /* |
678 | * This optimization is needed because alloc_ucounts() uses locks |
679 | * for table lookups. |
680 | */ |
681 | if (old_ucounts->ns == new->user_ns && uid_eq(left: old_ucounts->uid, right: new->uid)) |
682 | return 0; |
683 | |
684 | if (!(new_ucounts = alloc_ucounts(ns: new->user_ns, uid: new->uid))) |
685 | return -EAGAIN; |
686 | |
687 | new->ucounts = new_ucounts; |
688 | put_ucounts(ucounts: old_ucounts); |
689 | |
690 | return 0; |
691 | } |
692 | |
693 | /* |
694 | * initialise the credentials stuff |
695 | */ |
696 | void __init cred_init(void) |
697 | { |
698 | /* allocate a slab in which we can store credentials */ |
699 | cred_jar = kmem_cache_create(name: "cred_jar" , size: sizeof(struct cred), align: 0, |
700 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); |
701 | } |
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 | * |
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. |
714 | * |
715 | * The caller may change these controls afterwards if desired. |
716 | * |
717 | * Returns the new credentials or NULL if out of memory. |
718 | */ |
719 | struct cred *prepare_kernel_cred(struct task_struct *daemon) |
720 | { |
721 | const struct cred *old; |
722 | struct cred *new; |
723 | |
724 | if (WARN_ON_ONCE(!daemon)) |
725 | return NULL; |
726 | |
727 | new = kmem_cache_alloc(cachep: cred_jar, GFP_KERNEL); |
728 | if (!new) |
729 | return NULL; |
730 | |
731 | kdebug("prepare_kernel_cred() alloc %p" , new); |
732 | |
733 | old = get_task_cred(daemon); |
734 | validate_creds(old); |
735 | |
736 | *new = *old; |
737 | new->non_rcu = 0; |
738 | atomic_set(v: &new->usage, i: 1); |
739 | set_cred_subscribers(cred: new, n: 0); |
740 | get_uid(u: new->user); |
741 | get_user_ns(ns: new->user_ns); |
742 | get_group_info(gi: new->group_info); |
743 | |
744 | #ifdef CONFIG_KEYS |
745 | new->session_keyring = NULL; |
746 | new->process_keyring = NULL; |
747 | new->thread_keyring = NULL; |
748 | new->request_key_auth = NULL; |
749 | new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; |
750 | #endif |
751 | |
752 | #ifdef CONFIG_SECURITY |
753 | new->security = NULL; |
754 | #endif |
755 | new->ucounts = get_ucounts(ucounts: new->ucounts); |
756 | if (!new->ucounts) |
757 | goto error; |
758 | |
759 | if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) |
760 | goto error; |
761 | |
762 | put_cred(cred: old); |
763 | validate_creds(new); |
764 | return new; |
765 | |
766 | error: |
767 | put_cred(cred: new); |
768 | put_cred(cred: old); |
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(secdata: secctx, strlen(secctx), secid: &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 | { |
821 | if (!uid_valid(uid: inode->i_uid) || !gid_valid(gid: inode->i_gid)) |
822 | return -EINVAL; |
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); |
828 | |
829 | #ifdef CONFIG_DEBUG_CREDENTIALS |
830 | |
831 | bool creds_are_invalid(const struct cred *cred) |
832 | { |
833 | if (cred->magic != CRED_MAGIC) |
834 | return true; |
835 | return false; |
836 | } |
837 | EXPORT_SYMBOL(creds_are_invalid); |
838 | |
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 | { |
845 | pr_err("%s credentials: %p %s%s%s\n" , |
846 | label, cred, |
847 | cred == &init_cred ? "[init]" : "" , |
848 | cred == tsk->real_cred ? "[real]" : "" , |
849 | cred == tsk->cred ? "[eff]" : "" ); |
850 | pr_err("->magic=%x, put_addr=%p\n" , |
851 | cred->magic, cred->put_addr); |
852 | pr_err("->usage=%d, subscr=%d\n" , |
853 | atomic_read(&cred->usage), |
854 | read_cred_subscribers(cred)); |
855 | pr_err("->*uid = { %d,%d,%d,%d }\n" , |
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)); |
860 | pr_err("->*gid = { %d,%d,%d,%d }\n" , |
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)); |
865 | #ifdef CONFIG_SECURITY |
866 | pr_err("->security is %p\n" , cred->security); |
867 | if ((unsigned long) cred->security >= PAGE_SIZE && |
868 | (((unsigned long) cred->security & 0xffffff00) != |
869 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))) |
870 | pr_err("->security {%x, %x}\n" , |
871 | ((u32*)cred->security)[0], |
872 | ((u32*)cred->security)[1]); |
873 | #endif |
874 | } |
875 | |
876 | /* |
877 | * report use of invalid credentials |
878 | */ |
879 | void __noreturn __invalid_creds(const struct cred *cred, const char *file, unsigned line) |
880 | { |
881 | pr_err("Invalid credentials\n" ); |
882 | pr_err("At %s:%u\n" , file, line); |
883 | dump_invalid_creds(cred, label: "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: |
908 | pr_err("Invalid process credentials\n" ); |
909 | pr_err("At %s:%u\n" , file, line); |
910 | |
911 | dump_invalid_creds(cred: tsk->real_cred, label: "Real" , tsk); |
912 | if (tsk->cred != tsk->real_cred) |
913 | dump_invalid_creds(cred: tsk->cred, label: "Effective" , tsk); |
914 | else |
915 | pr_err("Effective creds == Real creds\n" ); |
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 */ |
934 | |