Merge tag 'gfs2-v5.13-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2...
[linux-2.6-microblaze.git] / kernel / cred.c
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 static 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         .ucounts                = &init_ucounts,
64 };
65
66 static inline void set_cred_subscribers(struct cred *cred, int n)
67 {
68 #ifdef CONFIG_DEBUG_CREDENTIALS
69         atomic_set(&cred->subscribers, n);
70 #endif
71 }
72
73 static inline int read_cred_subscribers(const struct cred *cred)
74 {
75 #ifdef CONFIG_DEBUG_CREDENTIALS
76         return atomic_read(&cred->subscribers);
77 #else
78         return 0;
79 #endif
80 }
81
82 static inline void alter_cred_subscribers(const struct cred *_cred, int n)
83 {
84 #ifdef CONFIG_DEBUG_CREDENTIALS
85         struct cred *cred = (struct cred *) _cred;
86
87         atomic_add(n, &cred->subscribers);
88 #endif
89 }
90
91 /*
92  * The RCU callback to actually dispose of a set of credentials
93  */
94 static void put_cred_rcu(struct rcu_head *rcu)
95 {
96         struct cred *cred = container_of(rcu, struct cred, rcu);
97
98         kdebug("put_cred_rcu(%p)", cred);
99
100 #ifdef CONFIG_DEBUG_CREDENTIALS
101         if (cred->magic != CRED_MAGIC_DEAD ||
102             atomic_read(&cred->usage) != 0 ||
103             read_cred_subscribers(cred) != 0)
104                 panic("CRED: put_cred_rcu() sees %p with"
105                       " mag %x, put %p, usage %d, subscr %d\n",
106                       cred, cred->magic, cred->put_addr,
107                       atomic_read(&cred->usage),
108                       read_cred_subscribers(cred));
109 #else
110         if (atomic_read(&cred->usage) != 0)
111                 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
112                       cred, atomic_read(&cred->usage));
113 #endif
114
115         security_cred_free(cred);
116         key_put(cred->session_keyring);
117         key_put(cred->process_keyring);
118         key_put(cred->thread_keyring);
119         key_put(cred->request_key_auth);
120         if (cred->group_info)
121                 put_group_info(cred->group_info);
122         free_uid(cred->user);
123         if (cred->ucounts)
124                 put_ucounts(cred->ucounts);
125         put_user_ns(cred->user_ns);
126         kmem_cache_free(cred_jar, cred);
127 }
128
129 /**
130  * __put_cred - Destroy a set of credentials
131  * @cred: The record to release
132  *
133  * Destroy a set of credentials on which no references remain.
134  */
135 void __put_cred(struct cred *cred)
136 {
137         kdebug("__put_cred(%p{%d,%d})", cred,
138                atomic_read(&cred->usage),
139                read_cred_subscribers(cred));
140
141         BUG_ON(atomic_read(&cred->usage) != 0);
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);
149
150         if (cred->non_rcu)
151                 put_cred_rcu(&cred->rcu);
152         else
153                 call_rcu(&cred->rcu, put_cred_rcu);
154 }
155 EXPORT_SYMBOL(__put_cred);
156
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);
179
180 #ifdef CONFIG_KEYS_REQUEST_CACHE
181         key_put(tsk->cached_requested_key);
182         tsk->cached_requested_key = NULL;
183 #endif
184 }
185
186 /**
187  * get_task_cred - Get another task's objective credentials
188  * @task: The task to query
189  *
190  * Get the objective credentials of a task, pinning them so that they can't go
191  * away.  Accessing a task's credentials directly is not permitted.
192  *
193  * The caller must also make sure task doesn't get deleted, either by holding a
194  * ref on task or by holding tasklist_lock to prevent it from being unlinked.
195  */
196 const struct cred *get_task_cred(struct task_struct *task)
197 {
198         const struct cred *cred;
199
200         rcu_read_lock();
201
202         do {
203                 cred = __task_cred((task));
204                 BUG_ON(!cred);
205         } while (!get_cred_rcu(cred));
206
207         rcu_read_unlock();
208         return cred;
209 }
210 EXPORT_SYMBOL(get_task_cred);
211
212 /*
213  * Allocate blank credentials, such that the credentials can be filled in at a
214  * later date without risk of ENOMEM.
215  */
216 struct cred *cred_alloc_blank(void)
217 {
218         struct cred *new;
219
220         new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
221         if (!new)
222                 return NULL;
223
224         atomic_set(&new->usage, 1);
225 #ifdef CONFIG_DEBUG_CREDENTIALS
226         new->magic = CRED_MAGIC;
227 #endif
228         new->ucounts = get_ucounts(&init_ucounts);
229
230         if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
231                 goto error;
232
233         return new;
234
235 error:
236         abort_creds(new);
237         return NULL;
238 }
239
240 /**
241  * prepare_creds - Prepare a new set of credentials for modification
242  *
243  * Prepare a new set of task credentials for modification.  A task's creds
244  * shouldn't generally be modified directly, therefore this function is used to
245  * prepare a new copy, which the caller then modifies and then commits by
246  * calling commit_creds().
247  *
248  * Preparation involves making a copy of the objective creds for modification.
249  *
250  * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
251  *
252  * Call commit_creds() or abort_creds() to clean up.
253  */
254 struct cred *prepare_creds(void)
255 {
256         struct task_struct *task = current;
257         const struct cred *old;
258         struct cred *new;
259
260         validate_process_creds();
261
262         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
263         if (!new)
264                 return NULL;
265
266         kdebug("prepare_creds() alloc %p", new);
267
268         old = task->cred;
269         memcpy(new, old, sizeof(struct cred));
270
271         new->non_rcu = 0;
272         atomic_set(&new->usage, 1);
273         set_cred_subscribers(new, 0);
274         get_group_info(new->group_info);
275         get_uid(new->user);
276         get_user_ns(new->user_ns);
277
278 #ifdef CONFIG_KEYS
279         key_get(new->session_keyring);
280         key_get(new->process_keyring);
281         key_get(new->thread_keyring);
282         key_get(new->request_key_auth);
283 #endif
284
285 #ifdef CONFIG_SECURITY
286         new->security = NULL;
287 #endif
288
289         if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
290                 goto error;
291
292         new->ucounts = get_ucounts(new->ucounts);
293         if (!new->ucounts)
294                 goto error;
295
296         validate_creds(new);
297         return new;
298
299 error:
300         abort_creds(new);
301         return NULL;
302 }
303 EXPORT_SYMBOL(prepare_creds);
304
305 /*
306  * Prepare credentials for current to perform an execve()
307  * - The caller must hold ->cred_guard_mutex
308  */
309 struct cred *prepare_exec_creds(void)
310 {
311         struct cred *new;
312
313         new = prepare_creds();
314         if (!new)
315                 return new;
316
317 #ifdef CONFIG_KEYS
318         /* newly exec'd tasks don't get a thread keyring */
319         key_put(new->thread_keyring);
320         new->thread_keyring = NULL;
321
322         /* inherit the session keyring; new process keyring */
323         key_put(new->process_keyring);
324         new->process_keyring = NULL;
325 #endif
326
327         new->suid = new->fsuid = new->euid;
328         new->sgid = new->fsgid = new->egid;
329
330         return new;
331 }
332
333 /*
334  * Copy credentials for the new process created by fork()
335  *
336  * We share if we can, but under some circumstances we have to generate a new
337  * set.
338  *
339  * The new process gets the current process's subjective credentials as its
340  * objective and subjective credentials
341  */
342 int copy_creds(struct task_struct *p, unsigned long clone_flags)
343 {
344         struct cred *new;
345         int ret;
346
347 #ifdef CONFIG_KEYS_REQUEST_CACHE
348         p->cached_requested_key = NULL;
349 #endif
350
351         if (
352 #ifdef CONFIG_KEYS
353                 !p->cred->thread_keyring &&
354 #endif
355                 clone_flags & CLONE_THREAD
356             ) {
357                 p->real_cred = get_cred(p->cred);
358                 get_cred(p->cred);
359                 alter_cred_subscribers(p->cred, 2);
360                 kdebug("share_creds(%p{%d,%d})",
361                        p->cred, atomic_read(&p->cred->usage),
362                        read_cred_subscribers(p->cred));
363                 inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
364                 return 0;
365         }
366
367         new = prepare_creds();
368         if (!new)
369                 return -ENOMEM;
370
371         if (clone_flags & CLONE_NEWUSER) {
372                 ret = create_user_ns(new);
373                 if (ret < 0)
374                         goto error_put;
375                 ret = set_cred_ucounts(new);
376                 if (ret < 0)
377                         goto error_put;
378         }
379
380 #ifdef CONFIG_KEYS
381         /* new threads get their own thread keyrings if their parent already
382          * had one */
383         if (new->thread_keyring) {
384                 key_put(new->thread_keyring);
385                 new->thread_keyring = NULL;
386                 if (clone_flags & CLONE_THREAD)
387                         install_thread_keyring_to_cred(new);
388         }
389
390         /* The process keyring is only shared between the threads in a process;
391          * anything outside of those threads doesn't inherit.
392          */
393         if (!(clone_flags & CLONE_THREAD)) {
394                 key_put(new->process_keyring);
395                 new->process_keyring = NULL;
396         }
397 #endif
398
399         p->cred = p->real_cred = get_cred(new);
400         inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
401         alter_cred_subscribers(new, 2);
402         validate_creds(new);
403         return 0;
404
405 error_put:
406         put_cred(new);
407         return ret;
408 }
409
410 static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
411 {
412         const struct user_namespace *set_ns = set->user_ns;
413         const struct user_namespace *subset_ns = subset->user_ns;
414
415         /* If the two credentials are in the same user namespace see if
416          * the capabilities of subset are a subset of set.
417          */
418         if (set_ns == subset_ns)
419                 return cap_issubset(subset->cap_permitted, set->cap_permitted);
420
421         /* The credentials are in a different user namespaces
422          * therefore one is a subset of the other only if a set is an
423          * ancestor of subset and set->euid is owner of subset or one
424          * of subsets ancestors.
425          */
426         for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
427                 if ((set_ns == subset_ns->parent)  &&
428                     uid_eq(subset_ns->owner, set->euid))
429                         return true;
430         }
431
432         return false;
433 }
434
435 /**
436  * commit_creds - Install new credentials upon the current task
437  * @new: The credentials to be assigned
438  *
439  * Install a new set of credentials to the current task, using RCU to replace
440  * the old set.  Both the objective and the subjective credentials pointers are
441  * updated.  This function may not be called if the subjective credentials are
442  * in an overridden state.
443  *
444  * This function eats the caller's reference to the new credentials.
445  *
446  * Always returns 0 thus allowing this function to be tail-called at the end
447  * of, say, sys_setgid().
448  */
449 int commit_creds(struct cred *new)
450 {
451         struct task_struct *task = current;
452         const struct cred *old = task->real_cred;
453
454         kdebug("commit_creds(%p{%d,%d})", new,
455                atomic_read(&new->usage),
456                read_cred_subscribers(new));
457
458         BUG_ON(task->cred != old);
459 #ifdef CONFIG_DEBUG_CREDENTIALS
460         BUG_ON(read_cred_subscribers(old) < 2);
461         validate_creds(old);
462         validate_creds(new);
463 #endif
464         BUG_ON(atomic_read(&new->usage) < 1);
465
466         get_cred(new); /* we will require a ref for the subj creds too */
467
468         /* dumpability changes */
469         if (!uid_eq(old->euid, new->euid) ||
470             !gid_eq(old->egid, new->egid) ||
471             !uid_eq(old->fsuid, new->fsuid) ||
472             !gid_eq(old->fsgid, new->fsgid) ||
473             !cred_cap_issubset(old, new)) {
474                 if (task->mm)
475                         set_dumpable(task->mm, suid_dumpable);
476                 task->pdeath_signal = 0;
477                 /*
478                  * If a task drops privileges and becomes nondumpable,
479                  * the dumpability change must become visible before
480                  * the credential change; otherwise, a __ptrace_may_access()
481                  * racing with this change may be able to attach to a task it
482                  * shouldn't be able to attach to (as if the task had dropped
483                  * privileges without becoming nondumpable).
484                  * Pairs with a read barrier in __ptrace_may_access().
485                  */
486                 smp_wmb();
487         }
488
489         /* alter the thread keyring */
490         if (!uid_eq(new->fsuid, old->fsuid))
491                 key_fsuid_changed(new);
492         if (!gid_eq(new->fsgid, old->fsgid))
493                 key_fsgid_changed(new);
494
495         /* do it
496          * RLIMIT_NPROC limits on user->processes have already been checked
497          * in set_user().
498          */
499         alter_cred_subscribers(new, 2);
500         if (new->user != old->user || new->user_ns != old->user_ns)
501                 inc_rlimit_ucounts(new->ucounts, UCOUNT_RLIMIT_NPROC, 1);
502         rcu_assign_pointer(task->real_cred, new);
503         rcu_assign_pointer(task->cred, new);
504         if (new->user != old->user)
505                 dec_rlimit_ucounts(old->ucounts, UCOUNT_RLIMIT_NPROC, 1);
506         alter_cred_subscribers(old, -2);
507
508         /* send notifications */
509         if (!uid_eq(new->uid,   old->uid)  ||
510             !uid_eq(new->euid,  old->euid) ||
511             !uid_eq(new->suid,  old->suid) ||
512             !uid_eq(new->fsuid, old->fsuid))
513                 proc_id_connector(task, PROC_EVENT_UID);
514
515         if (!gid_eq(new->gid,   old->gid)  ||
516             !gid_eq(new->egid,  old->egid) ||
517             !gid_eq(new->sgid,  old->sgid) ||
518             !gid_eq(new->fsgid, old->fsgid))
519                 proc_id_connector(task, PROC_EVENT_GID);
520
521         /* release the old obj and subj refs both */
522         put_cred(old);
523         put_cred(old);
524         return 0;
525 }
526 EXPORT_SYMBOL(commit_creds);
527
528 /**
529  * abort_creds - Discard a set of credentials and unlock the current task
530  * @new: The credentials that were going to be applied
531  *
532  * Discard a set of credentials that were under construction and unlock the
533  * current task.
534  */
535 void abort_creds(struct cred *new)
536 {
537         kdebug("abort_creds(%p{%d,%d})", new,
538                atomic_read(&new->usage),
539                read_cred_subscribers(new));
540
541 #ifdef CONFIG_DEBUG_CREDENTIALS
542         BUG_ON(read_cred_subscribers(new) != 0);
543 #endif
544         BUG_ON(atomic_read(&new->usage) < 1);
545         put_cred(new);
546 }
547 EXPORT_SYMBOL(abort_creds);
548
549 /**
550  * override_creds - Override the current process's subjective credentials
551  * @new: The credentials to be assigned
552  *
553  * Install a set of temporary override subjective credentials on the current
554  * process, returning the old set for later reversion.
555  */
556 const struct cred *override_creds(const struct cred *new)
557 {
558         const struct cred *old = current->cred;
559
560         kdebug("override_creds(%p{%d,%d})", new,
561                atomic_read(&new->usage),
562                read_cred_subscribers(new));
563
564         validate_creds(old);
565         validate_creds(new);
566
567         /*
568          * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
569          *
570          * That means that we do not clear the 'non_rcu' flag, since
571          * we are only installing the cred into the thread-synchronous
572          * '->cred' pointer, not the '->real_cred' pointer that is
573          * visible to other threads under RCU.
574          *
575          * Also note that we did validate_creds() manually, not depending
576          * on the validation in 'get_cred()'.
577          */
578         get_new_cred((struct cred *)new);
579         alter_cred_subscribers(new, 1);
580         rcu_assign_pointer(current->cred, new);
581         alter_cred_subscribers(old, -1);
582
583         kdebug("override_creds() = %p{%d,%d}", old,
584                atomic_read(&old->usage),
585                read_cred_subscribers(old));
586         return old;
587 }
588 EXPORT_SYMBOL(override_creds);
589
590 /**
591  * revert_creds - Revert a temporary subjective credentials override
592  * @old: The credentials to be restored
593  *
594  * Revert a temporary set of override subjective credentials to an old set,
595  * discarding the override set.
596  */
597 void revert_creds(const struct cred *old)
598 {
599         const struct cred *override = current->cred;
600
601         kdebug("revert_creds(%p{%d,%d})", old,
602                atomic_read(&old->usage),
603                read_cred_subscribers(old));
604
605         validate_creds(old);
606         validate_creds(override);
607         alter_cred_subscribers(old, 1);
608         rcu_assign_pointer(current->cred, old);
609         alter_cred_subscribers(override, -1);
610         put_cred(override);
611 }
612 EXPORT_SYMBOL(revert_creds);
613
614 /**
615  * cred_fscmp - Compare two credentials with respect to filesystem access.
616  * @a: The first credential
617  * @b: The second credential
618  *
619  * cred_cmp() will return zero if both credentials have the same
620  * fsuid, fsgid, and supplementary groups.  That is, if they will both
621  * provide the same access to files based on mode/uid/gid.
622  * If the credentials are different, then either -1 or 1 will
623  * be returned depending on whether @a comes before or after @b
624  * respectively in an arbitrary, but stable, ordering of credentials.
625  *
626  * Return: -1, 0, or 1 depending on comparison
627  */
628 int cred_fscmp(const struct cred *a, const struct cred *b)
629 {
630         struct group_info *ga, *gb;
631         int g;
632
633         if (a == b)
634                 return 0;
635         if (uid_lt(a->fsuid, b->fsuid))
636                 return -1;
637         if (uid_gt(a->fsuid, b->fsuid))
638                 return 1;
639
640         if (gid_lt(a->fsgid, b->fsgid))
641                 return -1;
642         if (gid_gt(a->fsgid, b->fsgid))
643                 return 1;
644
645         ga = a->group_info;
646         gb = b->group_info;
647         if (ga == gb)
648                 return 0;
649         if (ga == NULL)
650                 return -1;
651         if (gb == NULL)
652                 return 1;
653         if (ga->ngroups < gb->ngroups)
654                 return -1;
655         if (ga->ngroups > gb->ngroups)
656                 return 1;
657
658         for (g = 0; g < ga->ngroups; g++) {
659                 if (gid_lt(ga->gid[g], gb->gid[g]))
660                         return -1;
661                 if (gid_gt(ga->gid[g], gb->gid[g]))
662                         return 1;
663         }
664         return 0;
665 }
666 EXPORT_SYMBOL(cred_fscmp);
667
668 int set_cred_ucounts(struct cred *new)
669 {
670         struct task_struct *task = current;
671         const struct cred *old = task->real_cred;
672         struct ucounts *old_ucounts = new->ucounts;
673
674         if (new->user == old->user && new->user_ns == old->user_ns)
675                 return 0;
676
677         /*
678          * This optimization is needed because alloc_ucounts() uses locks
679          * for table lookups.
680          */
681         if (old_ucounts && old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid))
682                 return 0;
683
684         if (!(new->ucounts = alloc_ucounts(new->user_ns, new->euid)))
685                 return -EAGAIN;
686
687         if (old_ucounts)
688                 put_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("cred_jar", sizeof(struct cred), 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 for the security record, but can be NULL.
712  * If @daemon is supplied, then the security data will be derived from that;
713  * otherwise they'll be set to 0 and no groups, full 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         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
725         if (!new)
726                 return NULL;
727
728         kdebug("prepare_kernel_cred() alloc %p", new);
729
730         if (daemon)
731                 old = get_task_cred(daemon);
732         else
733                 old = get_cred(&init_cred);
734
735         validate_creds(old);
736
737         *new = *old;
738         new->non_rcu = 0;
739         atomic_set(&new->usage, 1);
740         set_cred_subscribers(new, 0);
741         get_uid(new->user);
742         get_user_ns(new->user_ns);
743         get_group_info(new->group_info);
744
745 #ifdef CONFIG_KEYS
746         new->session_keyring = NULL;
747         new->process_keyring = NULL;
748         new->thread_keyring = NULL;
749         new->request_key_auth = NULL;
750         new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
751 #endif
752
753 #ifdef CONFIG_SECURITY
754         new->security = NULL;
755 #endif
756         if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
757                 goto error;
758
759         new->ucounts = get_ucounts(new->ucounts);
760         if (!new->ucounts)
761                 goto error;
762
763         put_cred(old);
764         validate_creds(new);
765         return new;
766
767 error:
768         put_cred(new);
769         put_cred(old);
770         return NULL;
771 }
772 EXPORT_SYMBOL(prepare_kernel_cred);
773
774 /**
775  * set_security_override - Set the security ID in a set of credentials
776  * @new: The credentials to alter
777  * @secid: The LSM security ID to set
778  *
779  * Set the LSM security ID in a set of credentials so that the subjective
780  * security is overridden when an alternative set of credentials is used.
781  */
782 int set_security_override(struct cred *new, u32 secid)
783 {
784         return security_kernel_act_as(new, secid);
785 }
786 EXPORT_SYMBOL(set_security_override);
787
788 /**
789  * set_security_override_from_ctx - Set the security ID in a set of credentials
790  * @new: The credentials to alter
791  * @secctx: The LSM security context to generate the security ID from.
792  *
793  * Set the LSM security ID in a set of credentials so that the subjective
794  * security is overridden when an alternative set of credentials is used.  The
795  * security ID is specified in string form as a security context to be
796  * interpreted by the LSM.
797  */
798 int set_security_override_from_ctx(struct cred *new, const char *secctx)
799 {
800         u32 secid;
801         int ret;
802
803         ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
804         if (ret < 0)
805                 return ret;
806
807         return set_security_override(new, secid);
808 }
809 EXPORT_SYMBOL(set_security_override_from_ctx);
810
811 /**
812  * set_create_files_as - Set the LSM file create context in a set of credentials
813  * @new: The credentials to alter
814  * @inode: The inode to take the context from
815  *
816  * Change the LSM file creation context in a set of credentials to be the same
817  * as the object context of the specified inode, so that the new inodes have
818  * the same MAC context as that inode.
819  */
820 int set_create_files_as(struct cred *new, struct inode *inode)
821 {
822         if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
823                 return -EINVAL;
824         new->fsuid = inode->i_uid;
825         new->fsgid = inode->i_gid;
826         return security_kernel_create_files_as(new, inode);
827 }
828 EXPORT_SYMBOL(set_create_files_as);
829
830 #ifdef CONFIG_DEBUG_CREDENTIALS
831
832 bool creds_are_invalid(const struct cred *cred)
833 {
834         if (cred->magic != CRED_MAGIC)
835                 return true;
836         return false;
837 }
838 EXPORT_SYMBOL(creds_are_invalid);
839
840 /*
841  * dump invalid credentials
842  */
843 static void dump_invalid_creds(const struct cred *cred, const char *label,
844                                const struct task_struct *tsk)
845 {
846         printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
847                label, cred,
848                cred == &init_cred ? "[init]" : "",
849                cred == tsk->real_cred ? "[real]" : "",
850                cred == tsk->cred ? "[eff]" : "");
851         printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
852                cred->magic, cred->put_addr);
853         printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
854                atomic_read(&cred->usage),
855                read_cred_subscribers(cred));
856         printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
857                 from_kuid_munged(&init_user_ns, cred->uid),
858                 from_kuid_munged(&init_user_ns, cred->euid),
859                 from_kuid_munged(&init_user_ns, cred->suid),
860                 from_kuid_munged(&init_user_ns, cred->fsuid));
861         printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
862                 from_kgid_munged(&init_user_ns, cred->gid),
863                 from_kgid_munged(&init_user_ns, cred->egid),
864                 from_kgid_munged(&init_user_ns, cred->sgid),
865                 from_kgid_munged(&init_user_ns, cred->fsgid));
866 #ifdef CONFIG_SECURITY
867         printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
868         if ((unsigned long) cred->security >= PAGE_SIZE &&
869             (((unsigned long) cred->security & 0xffffff00) !=
870              (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
871                 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
872                        ((u32*)cred->security)[0],
873                        ((u32*)cred->security)[1]);
874 #endif
875 }
876
877 /*
878  * report use of invalid credentials
879  */
880 void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
881 {
882         printk(KERN_ERR "CRED: Invalid credentials\n");
883         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
884         dump_invalid_creds(cred, "Specified", current);
885         BUG();
886 }
887 EXPORT_SYMBOL(__invalid_creds);
888
889 /*
890  * check the credentials on a process
891  */
892 void __validate_process_creds(struct task_struct *tsk,
893                               const char *file, unsigned line)
894 {
895         if (tsk->cred == tsk->real_cred) {
896                 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
897                              creds_are_invalid(tsk->cred)))
898                         goto invalid_creds;
899         } else {
900                 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
901                              read_cred_subscribers(tsk->cred) < 1 ||
902                              creds_are_invalid(tsk->real_cred) ||
903                              creds_are_invalid(tsk->cred)))
904                         goto invalid_creds;
905         }
906         return;
907
908 invalid_creds:
909         printk(KERN_ERR "CRED: Invalid process credentials\n");
910         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
911
912         dump_invalid_creds(tsk->real_cred, "Real", tsk);
913         if (tsk->cred != tsk->real_cred)
914                 dump_invalid_creds(tsk->cred, "Effective", tsk);
915         else
916                 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
917         BUG();
918 }
919 EXPORT_SYMBOL(__validate_process_creds);
920
921 /*
922  * check creds for do_exit()
923  */
924 void validate_creds_for_do_exit(struct task_struct *tsk)
925 {
926         kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
927                tsk->real_cred, tsk->cred,
928                atomic_read(&tsk->cred->usage),
929                read_cred_subscribers(tsk->cred));
930
931         __validate_process_creds(tsk, __FILE__, __LINE__);
932 }
933
934 #endif /* CONFIG_DEBUG_CREDENTIALS */