[PATCH] Keys: Add possessor permissions to keys [try #3]
[linux-2.6.git] / security / keys / keyring.c
1 /* keyring.c: keyring handling
2  *
3  * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/sched.h>
15 #include <linux/slab.h>
16 #include <linux/seq_file.h>
17 #include <linux/err.h>
18 #include <asm/uaccess.h>
19 #include "internal.h"
20
21 /*
22  * when plumbing the depths of the key tree, this sets a hard limit set on how
23  * deep we're willing to go
24  */
25 #define KEYRING_SEARCH_MAX_DEPTH 6
26
27 /*
28  * we keep all named keyrings in a hash to speed looking them up
29  */
30 #define KEYRING_NAME_HASH_SIZE  (1 << 5)
31
32 static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
33 static DEFINE_RWLOCK(keyring_name_lock);
34
35 static inline unsigned keyring_hash(const char *desc)
36 {
37         unsigned bucket = 0;
38
39         for (; *desc; desc++)
40                 bucket += (unsigned char) *desc;
41
42         return bucket & (KEYRING_NAME_HASH_SIZE - 1);
43 }
44
45 /*
46  * the keyring type definition
47  */
48 static int keyring_instantiate(struct key *keyring,
49                                const void *data, size_t datalen);
50 static int keyring_duplicate(struct key *keyring, const struct key *source);
51 static int keyring_match(const struct key *keyring, const void *criterion);
52 static void keyring_destroy(struct key *keyring);
53 static void keyring_describe(const struct key *keyring, struct seq_file *m);
54 static long keyring_read(const struct key *keyring,
55                          char __user *buffer, size_t buflen);
56
57 struct key_type key_type_keyring = {
58         .name           = "keyring",
59         .def_datalen    = sizeof(struct keyring_list),
60         .instantiate    = keyring_instantiate,
61         .duplicate      = keyring_duplicate,
62         .match          = keyring_match,
63         .destroy        = keyring_destroy,
64         .describe       = keyring_describe,
65         .read           = keyring_read,
66 };
67
68 /*
69  * semaphore to serialise link/link calls to prevent two link calls in parallel
70  * introducing a cycle
71  */
72 DECLARE_RWSEM(keyring_serialise_link_sem);
73
74 /*****************************************************************************/
75 /*
76  * publish the name of a keyring so that it can be found by name (if it has
77  * one)
78  */
79 void keyring_publish_name(struct key *keyring)
80 {
81         int bucket;
82
83         if (keyring->description) {
84                 bucket = keyring_hash(keyring->description);
85
86                 write_lock(&keyring_name_lock);
87
88                 if (!keyring_name_hash[bucket].next)
89                         INIT_LIST_HEAD(&keyring_name_hash[bucket]);
90
91                 list_add_tail(&keyring->type_data.link,
92                               &keyring_name_hash[bucket]);
93
94                 write_unlock(&keyring_name_lock);
95         }
96
97 } /* end keyring_publish_name() */
98
99 /*****************************************************************************/
100 /*
101  * initialise a keyring
102  * - we object if we were given any data
103  */
104 static int keyring_instantiate(struct key *keyring,
105                                const void *data, size_t datalen)
106 {
107         int ret;
108
109         ret = -EINVAL;
110         if (datalen == 0) {
111                 /* make the keyring available by name if it has one */
112                 keyring_publish_name(keyring);
113                 ret = 0;
114         }
115
116         return ret;
117
118 } /* end keyring_instantiate() */
119
120 /*****************************************************************************/
121 /*
122  * duplicate the list of subscribed keys from a source keyring into this one
123  */
124 static int keyring_duplicate(struct key *keyring, const struct key *source)
125 {
126         struct keyring_list *sklist, *klist;
127         unsigned max;
128         size_t size;
129         int loop, ret;
130
131         const unsigned limit =
132                 (PAGE_SIZE - sizeof(*klist)) / sizeof(struct key *);
133
134         ret = 0;
135
136         /* find out how many keys are currently linked */
137         rcu_read_lock();
138         sklist = rcu_dereference(source->payload.subscriptions);
139         max = 0;
140         if (sklist)
141                 max = sklist->nkeys;
142         rcu_read_unlock();
143
144         /* allocate a new payload and stuff load with key links */
145         if (max > 0) {
146                 BUG_ON(max > limit);
147
148                 max = (max + 3) & ~3;
149                 if (max > limit)
150                         max = limit;
151
152                 ret = -ENOMEM;
153                 size = sizeof(*klist) + sizeof(struct key *) * max;
154                 klist = kmalloc(size, GFP_KERNEL);
155                 if (!klist)
156                         goto error;
157
158                 /* set links */
159                 rcu_read_lock();
160                 sklist = rcu_dereference(source->payload.subscriptions);
161
162                 klist->maxkeys = max;
163                 klist->nkeys = sklist->nkeys;
164                 memcpy(klist->keys,
165                        sklist->keys,
166                        sklist->nkeys * sizeof(struct key *));
167
168                 for (loop = klist->nkeys - 1; loop >= 0; loop--)
169                         atomic_inc(&klist->keys[loop]->usage);
170
171                 rcu_read_unlock();
172
173                 rcu_assign_pointer(keyring->payload.subscriptions, klist);
174                 ret = 0;
175         }
176
177  error:
178         return ret;
179
180 } /* end keyring_duplicate() */
181
182 /*****************************************************************************/
183 /*
184  * match keyrings on their name
185  */
186 static int keyring_match(const struct key *keyring, const void *description)
187 {
188         return keyring->description &&
189                 strcmp(keyring->description, description) == 0;
190
191 } /* end keyring_match() */
192
193 /*****************************************************************************/
194 /*
195  * dispose of the data dangling from the corpse of a keyring
196  */
197 static void keyring_destroy(struct key *keyring)
198 {
199         struct keyring_list *klist;
200         int loop;
201
202         if (keyring->description) {
203                 write_lock(&keyring_name_lock);
204
205                 if (keyring->type_data.link.next != NULL &&
206                     !list_empty(&keyring->type_data.link))
207                         list_del(&keyring->type_data.link);
208
209                 write_unlock(&keyring_name_lock);
210         }
211
212         klist = rcu_dereference(keyring->payload.subscriptions);
213         if (klist) {
214                 for (loop = klist->nkeys - 1; loop >= 0; loop--)
215                         key_put(klist->keys[loop]);
216                 kfree(klist);
217         }
218
219 } /* end keyring_destroy() */
220
221 /*****************************************************************************/
222 /*
223  * describe the keyring
224  */
225 static void keyring_describe(const struct key *keyring, struct seq_file *m)
226 {
227         struct keyring_list *klist;
228
229         if (keyring->description) {
230                 seq_puts(m, keyring->description);
231         }
232         else {
233                 seq_puts(m, "[anon]");
234         }
235
236         rcu_read_lock();
237         klist = rcu_dereference(keyring->payload.subscriptions);
238         if (klist)
239                 seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
240         else
241                 seq_puts(m, ": empty");
242         rcu_read_unlock();
243
244 } /* end keyring_describe() */
245
246 /*****************************************************************************/
247 /*
248  * read a list of key IDs from the keyring's contents
249  * - the keyring's semaphore is read-locked
250  */
251 static long keyring_read(const struct key *keyring,
252                          char __user *buffer, size_t buflen)
253 {
254         struct keyring_list *klist;
255         struct key *key;
256         size_t qty, tmp;
257         int loop, ret;
258
259         ret = 0;
260         klist = rcu_dereference(keyring->payload.subscriptions);
261
262         if (klist) {
263                 /* calculate how much data we could return */
264                 qty = klist->nkeys * sizeof(key_serial_t);
265
266                 if (buffer && buflen > 0) {
267                         if (buflen > qty)
268                                 buflen = qty;
269
270                         /* copy the IDs of the subscribed keys into the
271                          * buffer */
272                         ret = -EFAULT;
273
274                         for (loop = 0; loop < klist->nkeys; loop++) {
275                                 key = klist->keys[loop];
276
277                                 tmp = sizeof(key_serial_t);
278                                 if (tmp > buflen)
279                                         tmp = buflen;
280
281                                 if (copy_to_user(buffer,
282                                                  &key->serial,
283                                                  tmp) != 0)
284                                         goto error;
285
286                                 buflen -= tmp;
287                                 if (buflen == 0)
288                                         break;
289                                 buffer += tmp;
290                         }
291                 }
292
293                 ret = qty;
294         }
295
296  error:
297         return ret;
298
299 } /* end keyring_read() */
300
301 /*****************************************************************************/
302 /*
303  * allocate a keyring and link into the destination keyring
304  */
305 struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
306                           int not_in_quota, struct key *dest)
307 {
308         struct key *keyring;
309         int ret;
310
311         keyring = key_alloc(&key_type_keyring, description,
312                             uid, gid, KEY_POS_ALL | KEY_USR_ALL, not_in_quota);
313
314         if (!IS_ERR(keyring)) {
315                 ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
316                 if (ret < 0) {
317                         key_put(keyring);
318                         keyring = ERR_PTR(ret);
319                 }
320         }
321
322         return keyring;
323
324 } /* end keyring_alloc() */
325
326 /*****************************************************************************/
327 /*
328  * search the supplied keyring tree for a key that matches the criterion
329  * - perform a breadth-then-depth search up to the prescribed limit
330  * - we only find keys on which we have search permission
331  * - we use the supplied match function to see if the description (or other
332  *   feature of interest) matches
333  * - we rely on RCU to prevent the keyring lists from disappearing on us
334  * - we return -EAGAIN if we didn't find any matching key
335  * - we return -ENOKEY if we only found negative matching keys
336  * - we propagate the possession attribute from the keyring ref to the key ref
337  */
338 key_ref_t keyring_search_aux(key_ref_t keyring_ref,
339                              struct task_struct *context,
340                              struct key_type *type,
341                              const void *description,
342                              key_match_func_t match)
343 {
344         struct {
345                 struct keyring_list *keylist;
346                 int kix;
347         } stack[KEYRING_SEARCH_MAX_DEPTH];
348
349         struct keyring_list *keylist;
350         struct timespec now;
351         unsigned long possessed;
352         struct key *keyring, *key;
353         key_ref_t key_ref;
354         long err;
355         int sp, kix;
356
357         keyring = key_ref_to_ptr(keyring_ref);
358         possessed = is_key_possessed(keyring_ref);
359         key_check(keyring);
360
361         /* top keyring must have search permission to begin the search */
362         key_ref = ERR_PTR(-EACCES);
363         if (!key_task_permission(keyring_ref, context, KEY_SEARCH))
364                 goto error;
365
366         key_ref = ERR_PTR(-ENOTDIR);
367         if (keyring->type != &key_type_keyring)
368                 goto error;
369
370         rcu_read_lock();
371
372         now = current_kernel_time();
373         err = -EAGAIN;
374         sp = 0;
375
376         /* start processing a new keyring */
377 descend:
378         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
379                 goto not_this_keyring;
380
381         keylist = rcu_dereference(keyring->payload.subscriptions);
382         if (!keylist)
383                 goto not_this_keyring;
384
385         /* iterate through the keys in this keyring first */
386         for (kix = 0; kix < keylist->nkeys; kix++) {
387                 key = keylist->keys[kix];
388
389                 /* ignore keys not of this type */
390                 if (key->type != type)
391                         continue;
392
393                 /* skip revoked keys and expired keys */
394                 if (test_bit(KEY_FLAG_REVOKED, &key->flags))
395                         continue;
396
397                 if (key->expiry && now.tv_sec >= key->expiry)
398                         continue;
399
400                 /* keys that don't match */
401                 if (!match(key, description))
402                         continue;
403
404                 /* key must have search permissions */
405                 if (!key_task_permission(make_key_ref(key, possessed),
406                                          context, KEY_SEARCH))
407                         continue;
408
409                 /* we set a different error code if we find a negative key */
410                 if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
411                         err = -ENOKEY;
412                         continue;
413                 }
414
415                 goto found;
416         }
417
418         /* search through the keyrings nested in this one */
419         kix = 0;
420 ascend:
421         for (; kix < keylist->nkeys; kix++) {
422                 key = keylist->keys[kix];
423                 if (key->type != &key_type_keyring)
424                         continue;
425
426                 /* recursively search nested keyrings
427                  * - only search keyrings for which we have search permission
428                  */
429                 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
430                         continue;
431
432                 if (!key_task_permission(make_key_ref(key, possessed),
433                                          context, KEY_SEARCH))
434                         continue;
435
436                 /* stack the current position */
437                 stack[sp].keylist = keylist;
438                 stack[sp].kix = kix;
439                 sp++;
440
441                 /* begin again with the new keyring */
442                 keyring = key;
443                 goto descend;
444         }
445
446         /* the keyring we're looking at was disqualified or didn't contain a
447          * matching key */
448 not_this_keyring:
449         if (sp > 0) {
450                 /* resume the processing of a keyring higher up in the tree */
451                 sp--;
452                 keylist = stack[sp].keylist;
453                 kix = stack[sp].kix + 1;
454                 goto ascend;
455         }
456
457         key_ref = ERR_PTR(err);
458         goto error_2;
459
460         /* we found a viable match */
461 found:
462         atomic_inc(&key->usage);
463         key_check(key);
464         key_ref = make_key_ref(key, possessed);
465 error_2:
466         rcu_read_unlock();
467 error:
468         return key_ref;
469
470 } /* end keyring_search_aux() */
471
472 /*****************************************************************************/
473 /*
474  * search the supplied keyring tree for a key that matches the criterion
475  * - perform a breadth-then-depth search up to the prescribed limit
476  * - we only find keys on which we have search permission
477  * - we readlock the keyrings as we search down the tree
478  * - we return -EAGAIN if we didn't find any matching key
479  * - we return -ENOKEY if we only found negative matching keys
480  */
481 key_ref_t keyring_search(key_ref_t keyring,
482                          struct key_type *type,
483                          const char *description)
484 {
485         if (!type->match)
486                 return ERR_PTR(-ENOKEY);
487
488         return keyring_search_aux(keyring, current,
489                                   type, description, type->match);
490
491 } /* end keyring_search() */
492
493 EXPORT_SYMBOL(keyring_search);
494
495 /*****************************************************************************/
496 /*
497  * search the given keyring only (no recursion)
498  * - keyring must be locked by caller
499  */
500 key_ref_t __keyring_search_one(key_ref_t keyring_ref,
501                                const struct key_type *ktype,
502                                const char *description,
503                                key_perm_t perm)
504 {
505         struct keyring_list *klist;
506         unsigned long possessed;
507         struct key *keyring, *key;
508         int loop;
509
510         keyring = key_ref_to_ptr(keyring_ref);
511         possessed = is_key_possessed(keyring_ref);
512
513         rcu_read_lock();
514
515         klist = rcu_dereference(keyring->payload.subscriptions);
516         if (klist) {
517                 for (loop = 0; loop < klist->nkeys; loop++) {
518                         key = klist->keys[loop];
519
520                         if (key->type == ktype &&
521                             (!key->type->match ||
522                              key->type->match(key, description)) &&
523                             key_permission(make_key_ref(key, possessed),
524                                            perm) &&
525                             !test_bit(KEY_FLAG_REVOKED, &key->flags)
526                             )
527                                 goto found;
528                 }
529         }
530
531         rcu_read_unlock();
532         return ERR_PTR(-ENOKEY);
533
534  found:
535         atomic_inc(&key->usage);
536         rcu_read_unlock();
537         return make_key_ref(key, possessed);
538
539 } /* end __keyring_search_one() */
540
541 /*****************************************************************************/
542 /*
543  * search for an instantiation authorisation key matching a target key
544  * - the RCU read lock must be held by the caller
545  * - a target_id of zero specifies any valid token
546  */
547 struct key *keyring_search_instkey(struct key *keyring,
548                                    key_serial_t target_id)
549 {
550         struct request_key_auth *rka;
551         struct keyring_list *klist;
552         struct key *instkey;
553         int loop;
554
555         klist = rcu_dereference(keyring->payload.subscriptions);
556         if (klist) {
557                 for (loop = 0; loop < klist->nkeys; loop++) {
558                         instkey = klist->keys[loop];
559
560                         if (instkey->type != &key_type_request_key_auth)
561                                 continue;
562
563                         rka = instkey->payload.data;
564                         if (target_id && rka->target_key->serial != target_id)
565                                 continue;
566
567                         /* the auth key is revoked during instantiation */
568                         if (!test_bit(KEY_FLAG_REVOKED, &instkey->flags))
569                                 goto found;
570
571                         instkey = ERR_PTR(-EKEYREVOKED);
572                         goto error;
573                 }
574         }
575
576         instkey = ERR_PTR(-EACCES);
577         goto error;
578
579 found:
580         atomic_inc(&instkey->usage);
581 error:
582         return instkey;
583
584 } /* end keyring_search_instkey() */
585
586 /*****************************************************************************/
587 /*
588  * find a keyring with the specified name
589  * - all named keyrings are searched
590  * - only find keyrings with search permission for the process
591  * - only find keyrings with a serial number greater than the one specified
592  */
593 struct key *find_keyring_by_name(const char *name, key_serial_t bound)
594 {
595         struct key *keyring;
596         int bucket;
597
598         keyring = ERR_PTR(-EINVAL);
599         if (!name)
600                 goto error;
601
602         bucket = keyring_hash(name);
603
604         read_lock(&keyring_name_lock);
605
606         if (keyring_name_hash[bucket].next) {
607                 /* search this hash bucket for a keyring with a matching name
608                  * that's readable and that hasn't been revoked */
609                 list_for_each_entry(keyring,
610                                     &keyring_name_hash[bucket],
611                                     type_data.link
612                                     ) {
613                         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
614                                 continue;
615
616                         if (strcmp(keyring->description, name) != 0)
617                                 continue;
618
619                         if (!key_permission(make_key_ref(keyring, 0),
620                                             KEY_SEARCH))
621                                 continue;
622
623                         /* found a potential candidate, but we still need to
624                          * check the serial number */
625                         if (keyring->serial <= bound)
626                                 continue;
627
628                         /* we've got a match */
629                         atomic_inc(&keyring->usage);
630                         read_unlock(&keyring_name_lock);
631                         goto error;
632                 }
633         }
634
635         read_unlock(&keyring_name_lock);
636         keyring = ERR_PTR(-ENOKEY);
637
638  error:
639         return keyring;
640
641 } /* end find_keyring_by_name() */
642
643 /*****************************************************************************/
644 /*
645  * see if a cycle will will be created by inserting acyclic tree B in acyclic
646  * tree A at the topmost level (ie: as a direct child of A)
647  * - since we are adding B to A at the top level, checking for cycles should
648  *   just be a matter of seeing if node A is somewhere in tree B
649  */
650 static int keyring_detect_cycle(struct key *A, struct key *B)
651 {
652         struct {
653                 struct keyring_list *keylist;
654                 int kix;
655         } stack[KEYRING_SEARCH_MAX_DEPTH];
656
657         struct keyring_list *keylist;
658         struct key *subtree, *key;
659         int sp, kix, ret;
660
661         rcu_read_lock();
662
663         ret = -EDEADLK;
664         if (A == B)
665                 goto cycle_detected;
666
667         subtree = B;
668         sp = 0;
669
670         /* start processing a new keyring */
671  descend:
672         if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
673                 goto not_this_keyring;
674
675         keylist = rcu_dereference(subtree->payload.subscriptions);
676         if (!keylist)
677                 goto not_this_keyring;
678         kix = 0;
679
680  ascend:
681         /* iterate through the remaining keys in this keyring */
682         for (; kix < keylist->nkeys; kix++) {
683                 key = keylist->keys[kix];
684
685                 if (key == A)
686                         goto cycle_detected;
687
688                 /* recursively check nested keyrings */
689                 if (key->type == &key_type_keyring) {
690                         if (sp >= KEYRING_SEARCH_MAX_DEPTH)
691                                 goto too_deep;
692
693                         /* stack the current position */
694                         stack[sp].keylist = keylist;
695                         stack[sp].kix = kix;
696                         sp++;
697
698                         /* begin again with the new keyring */
699                         subtree = key;
700                         goto descend;
701                 }
702         }
703
704         /* the keyring we're looking at was disqualified or didn't contain a
705          * matching key */
706  not_this_keyring:
707         if (sp > 0) {
708                 /* resume the checking of a keyring higher up in the tree */
709                 sp--;
710                 keylist = stack[sp].keylist;
711                 kix = stack[sp].kix + 1;
712                 goto ascend;
713         }
714
715         ret = 0; /* no cycles detected */
716
717  error:
718         rcu_read_unlock();
719         return ret;
720
721  too_deep:
722         ret = -ELOOP;
723         goto error;
724
725  cycle_detected:
726         ret = -EDEADLK;
727         goto error;
728
729 } /* end keyring_detect_cycle() */
730
731 /*****************************************************************************/
732 /*
733  * dispose of a keyring list after the RCU grace period
734  */
735 static void keyring_link_rcu_disposal(struct rcu_head *rcu)
736 {
737         struct keyring_list *klist =
738                 container_of(rcu, struct keyring_list, rcu);
739
740         kfree(klist);
741
742 } /* end keyring_link_rcu_disposal() */
743
744 /*****************************************************************************/
745 /*
746  * link a key into to a keyring
747  * - must be called with the keyring's semaphore write-locked
748  */
749 int __key_link(struct key *keyring, struct key *key)
750 {
751         struct keyring_list *klist, *nklist;
752         unsigned max;
753         size_t size;
754         int ret;
755
756         ret = -EKEYREVOKED;
757         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
758                 goto error;
759
760         ret = -ENOTDIR;
761         if (keyring->type != &key_type_keyring)
762                 goto error;
763
764         /* serialise link/link calls to prevent parallel calls causing a
765          * cycle when applied to two keyring in opposite orders */
766         down_write(&keyring_serialise_link_sem);
767
768         /* check that we aren't going to create a cycle adding one keyring to
769          * another */
770         if (key->type == &key_type_keyring) {
771                 ret = keyring_detect_cycle(keyring, key);
772                 if (ret < 0)
773                         goto error2;
774         }
775
776         /* check that we aren't going to overrun the user's quota */
777         ret = key_payload_reserve(keyring,
778                                   keyring->datalen + KEYQUOTA_LINK_BYTES);
779         if (ret < 0)
780                 goto error2;
781
782         klist = keyring->payload.subscriptions;
783
784         if (klist && klist->nkeys < klist->maxkeys) {
785                 /* there's sufficient slack space to add directly */
786                 atomic_inc(&key->usage);
787
788                 klist->keys[klist->nkeys] = key;
789                 smp_wmb();
790                 klist->nkeys++;
791                 smp_wmb();
792
793                 ret = 0;
794         }
795         else {
796                 /* grow the key list */
797                 max = 4;
798                 if (klist)
799                         max += klist->maxkeys;
800
801                 ret = -ENFILE;
802                 if (max > 65535)
803                         goto error3;
804                 size = sizeof(*klist) + sizeof(struct key *) * max;
805                 if (size > PAGE_SIZE)
806                         goto error3;
807
808                 ret = -ENOMEM;
809                 nklist = kmalloc(size, GFP_KERNEL);
810                 if (!nklist)
811                         goto error3;
812                 nklist->maxkeys = max;
813                 nklist->nkeys = 0;
814
815                 if (klist) {
816                         nklist->nkeys = klist->nkeys;
817                         memcpy(nklist->keys,
818                                klist->keys,
819                                sizeof(struct key *) * klist->nkeys);
820                 }
821
822                 /* add the key into the new space */
823                 atomic_inc(&key->usage);
824                 nklist->keys[nklist->nkeys++] = key;
825
826                 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
827
828                 /* dispose of the old keyring list */
829                 if (klist)
830                         call_rcu(&klist->rcu, keyring_link_rcu_disposal);
831
832                 ret = 0;
833         }
834
835  error2:
836         up_write(&keyring_serialise_link_sem);
837  error:
838         return ret;
839
840  error3:
841         /* undo the quota changes */
842         key_payload_reserve(keyring,
843                             keyring->datalen - KEYQUOTA_LINK_BYTES);
844         goto error2;
845
846 } /* end __key_link() */
847
848 /*****************************************************************************/
849 /*
850  * link a key to a keyring
851  */
852 int key_link(struct key *keyring, struct key *key)
853 {
854         int ret;
855
856         key_check(keyring);
857         key_check(key);
858
859         down_write(&keyring->sem);
860         ret = __key_link(keyring, key);
861         up_write(&keyring->sem);
862
863         return ret;
864
865 } /* end key_link() */
866
867 EXPORT_SYMBOL(key_link);
868
869 /*****************************************************************************/
870 /*
871  * dispose of a keyring list after the RCU grace period, freeing the unlinked
872  * key
873  */
874 static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
875 {
876         struct keyring_list *klist =
877                 container_of(rcu, struct keyring_list, rcu);
878
879         key_put(klist->keys[klist->delkey]);
880         kfree(klist);
881
882 } /* end keyring_unlink_rcu_disposal() */
883
884 /*****************************************************************************/
885 /*
886  * unlink the first link to a key from a keyring
887  */
888 int key_unlink(struct key *keyring, struct key *key)
889 {
890         struct keyring_list *klist, *nklist;
891         int loop, ret;
892
893         key_check(keyring);
894         key_check(key);
895
896         ret = -ENOTDIR;
897         if (keyring->type != &key_type_keyring)
898                 goto error;
899
900         down_write(&keyring->sem);
901
902         klist = keyring->payload.subscriptions;
903         if (klist) {
904                 /* search the keyring for the key */
905                 for (loop = 0; loop < klist->nkeys; loop++)
906                         if (klist->keys[loop] == key)
907                                 goto key_is_present;
908         }
909
910         up_write(&keyring->sem);
911         ret = -ENOENT;
912         goto error;
913
914 key_is_present:
915         /* we need to copy the key list for RCU purposes */
916         nklist = kmalloc(sizeof(*klist) +
917                          sizeof(struct key *) * klist->maxkeys,
918                          GFP_KERNEL);
919         if (!nklist)
920                 goto nomem;
921         nklist->maxkeys = klist->maxkeys;
922         nklist->nkeys = klist->nkeys - 1;
923
924         if (loop > 0)
925                 memcpy(&nklist->keys[0],
926                        &klist->keys[0],
927                        loop * sizeof(struct key *));
928
929         if (loop < nklist->nkeys)
930                 memcpy(&nklist->keys[loop],
931                        &klist->keys[loop + 1],
932                        (nklist->nkeys - loop) * sizeof(struct key *));
933
934         /* adjust the user's quota */
935         key_payload_reserve(keyring,
936                             keyring->datalen - KEYQUOTA_LINK_BYTES);
937
938         rcu_assign_pointer(keyring->payload.subscriptions, nklist);
939
940         up_write(&keyring->sem);
941
942         /* schedule for later cleanup */
943         klist->delkey = loop;
944         call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
945
946         ret = 0;
947
948 error:
949         return ret;
950 nomem:
951         ret = -ENOMEM;
952         up_write(&keyring->sem);
953         goto error;
954
955 } /* end key_unlink() */
956
957 EXPORT_SYMBOL(key_unlink);
958
959 /*****************************************************************************/
960 /*
961  * dispose of a keyring list after the RCU grace period, releasing the keys it
962  * links to
963  */
964 static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
965 {
966         struct keyring_list *klist;
967         int loop;
968
969         klist = container_of(rcu, struct keyring_list, rcu);
970
971         for (loop = klist->nkeys - 1; loop >= 0; loop--)
972                 key_put(klist->keys[loop]);
973
974         kfree(klist);
975
976 } /* end keyring_clear_rcu_disposal() */
977
978 /*****************************************************************************/
979 /*
980  * clear the specified process keyring
981  * - implements keyctl(KEYCTL_CLEAR)
982  */
983 int keyring_clear(struct key *keyring)
984 {
985         struct keyring_list *klist;
986         int ret;
987
988         ret = -ENOTDIR;
989         if (keyring->type == &key_type_keyring) {
990                 /* detach the pointer block with the locks held */
991                 down_write(&keyring->sem);
992
993                 klist = keyring->payload.subscriptions;
994                 if (klist) {
995                         /* adjust the quota */
996                         key_payload_reserve(keyring,
997                                             sizeof(struct keyring_list));
998
999                         rcu_assign_pointer(keyring->payload.subscriptions,
1000                                            NULL);
1001                 }
1002
1003                 up_write(&keyring->sem);
1004
1005                 /* free the keys after the locks have been dropped */
1006                 if (klist)
1007                         call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
1008
1009                 ret = 0;
1010         }
1011
1012         return ret;
1013
1014 } /* end keyring_clear() */
1015
1016 EXPORT_SYMBOL(keyring_clear);