70f0c313c888bd7dd88963c61b2c5f5258d454e6
[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/security.h>
17 #include <linux/seq_file.h>
18 #include <linux/err.h>
19 #include <asm/uaccess.h>
20 #include "internal.h"
21
22 /*
23  * when plumbing the depths of the key tree, this sets a hard limit set on how
24  * deep we're willing to go
25  */
26 #define KEYRING_SEARCH_MAX_DEPTH 6
27
28 /*
29  * we keep all named keyrings in a hash to speed looking them up
30  */
31 #define KEYRING_NAME_HASH_SIZE  (1 << 5)
32
33 static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
34 static DEFINE_RWLOCK(keyring_name_lock);
35
36 static inline unsigned keyring_hash(const char *desc)
37 {
38         unsigned bucket = 0;
39
40         for (; *desc; desc++)
41                 bucket += (unsigned char) *desc;
42
43         return bucket & (KEYRING_NAME_HASH_SIZE - 1);
44 }
45
46 /*
47  * the keyring type definition
48  */
49 static int keyring_instantiate(struct key *keyring,
50                                const void *data, size_t datalen);
51 static int keyring_match(const struct key *keyring, const void *criterion);
52 static void keyring_revoke(struct key *keyring);
53 static void keyring_destroy(struct key *keyring);
54 static void keyring_describe(const struct key *keyring, struct seq_file *m);
55 static long keyring_read(const struct key *keyring,
56                          char __user *buffer, size_t buflen);
57
58 struct key_type key_type_keyring = {
59         .name           = "keyring",
60         .def_datalen    = sizeof(struct keyring_list),
61         .instantiate    = keyring_instantiate,
62         .match          = keyring_match,
63         .revoke         = keyring_revoke,
64         .destroy        = keyring_destroy,
65         .describe       = keyring_describe,
66         .read           = keyring_read,
67 };
68
69 EXPORT_SYMBOL(key_type_keyring);
70
71 /*
72  * semaphore to serialise link/link calls to prevent two link calls in parallel
73  * introducing a cycle
74  */
75 static DECLARE_RWSEM(keyring_serialise_link_sem);
76
77 /*****************************************************************************/
78 /*
79  * publish the name of a keyring so that it can be found by name (if it has
80  * one)
81  */
82 void keyring_publish_name(struct key *keyring)
83 {
84         int bucket;
85
86         if (keyring->description) {
87                 bucket = keyring_hash(keyring->description);
88
89                 write_lock(&keyring_name_lock);
90
91                 if (!keyring_name_hash[bucket].next)
92                         INIT_LIST_HEAD(&keyring_name_hash[bucket]);
93
94                 list_add_tail(&keyring->type_data.link,
95                               &keyring_name_hash[bucket]);
96
97                 write_unlock(&keyring_name_lock);
98         }
99
100 } /* end keyring_publish_name() */
101
102 /*****************************************************************************/
103 /*
104  * initialise a keyring
105  * - we object if we were given any data
106  */
107 static int keyring_instantiate(struct key *keyring,
108                                const void *data, size_t datalen)
109 {
110         int ret;
111
112         ret = -EINVAL;
113         if (datalen == 0) {
114                 /* make the keyring available by name if it has one */
115                 keyring_publish_name(keyring);
116                 ret = 0;
117         }
118
119         return ret;
120
121 } /* end keyring_instantiate() */
122
123 /*****************************************************************************/
124 /*
125  * match keyrings on their name
126  */
127 static int keyring_match(const struct key *keyring, const void *description)
128 {
129         return keyring->description &&
130                 strcmp(keyring->description, description) == 0;
131
132 } /* end keyring_match() */
133
134 /*****************************************************************************/
135 /*
136  * dispose of the data dangling from the corpse of a keyring
137  */
138 static void keyring_destroy(struct key *keyring)
139 {
140         struct keyring_list *klist;
141         int loop;
142
143         if (keyring->description) {
144                 write_lock(&keyring_name_lock);
145
146                 if (keyring->type_data.link.next != NULL &&
147                     !list_empty(&keyring->type_data.link))
148                         list_del(&keyring->type_data.link);
149
150                 write_unlock(&keyring_name_lock);
151         }
152
153         klist = rcu_dereference(keyring->payload.subscriptions);
154         if (klist) {
155                 for (loop = klist->nkeys - 1; loop >= 0; loop--)
156                         key_put(klist->keys[loop]);
157                 kfree(klist);
158         }
159
160 } /* end keyring_destroy() */
161
162 /*****************************************************************************/
163 /*
164  * describe the keyring
165  */
166 static void keyring_describe(const struct key *keyring, struct seq_file *m)
167 {
168         struct keyring_list *klist;
169
170         if (keyring->description) {
171                 seq_puts(m, keyring->description);
172         }
173         else {
174                 seq_puts(m, "[anon]");
175         }
176
177         rcu_read_lock();
178         klist = rcu_dereference(keyring->payload.subscriptions);
179         if (klist)
180                 seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
181         else
182                 seq_puts(m, ": empty");
183         rcu_read_unlock();
184
185 } /* end keyring_describe() */
186
187 /*****************************************************************************/
188 /*
189  * read a list of key IDs from the keyring's contents
190  * - the keyring's semaphore is read-locked
191  */
192 static long keyring_read(const struct key *keyring,
193                          char __user *buffer, size_t buflen)
194 {
195         struct keyring_list *klist;
196         struct key *key;
197         size_t qty, tmp;
198         int loop, ret;
199
200         ret = 0;
201         klist = rcu_dereference(keyring->payload.subscriptions);
202
203         if (klist) {
204                 /* calculate how much data we could return */
205                 qty = klist->nkeys * sizeof(key_serial_t);
206
207                 if (buffer && buflen > 0) {
208                         if (buflen > qty)
209                                 buflen = qty;
210
211                         /* copy the IDs of the subscribed keys into the
212                          * buffer */
213                         ret = -EFAULT;
214
215                         for (loop = 0; loop < klist->nkeys; loop++) {
216                                 key = klist->keys[loop];
217
218                                 tmp = sizeof(key_serial_t);
219                                 if (tmp > buflen)
220                                         tmp = buflen;
221
222                                 if (copy_to_user(buffer,
223                                                  &key->serial,
224                                                  tmp) != 0)
225                                         goto error;
226
227                                 buflen -= tmp;
228                                 if (buflen == 0)
229                                         break;
230                                 buffer += tmp;
231                         }
232                 }
233
234                 ret = qty;
235         }
236
237  error:
238         return ret;
239
240 } /* end keyring_read() */
241
242 /*****************************************************************************/
243 /*
244  * allocate a keyring and link into the destination keyring
245  */
246 struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
247                           struct task_struct *ctx, unsigned long flags,
248                           struct key *dest)
249 {
250         struct key *keyring;
251         int ret;
252
253         keyring = key_alloc(&key_type_keyring, description,
254                             uid, gid, ctx,
255                             (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
256                             flags);
257
258         if (!IS_ERR(keyring)) {
259                 ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
260                 if (ret < 0) {
261                         key_put(keyring);
262                         keyring = ERR_PTR(ret);
263                 }
264         }
265
266         return keyring;
267
268 } /* end keyring_alloc() */
269
270 /*****************************************************************************/
271 /*
272  * search the supplied keyring tree for a key that matches the criterion
273  * - perform a breadth-then-depth search up to the prescribed limit
274  * - we only find keys on which we have search permission
275  * - we use the supplied match function to see if the description (or other
276  *   feature of interest) matches
277  * - we rely on RCU to prevent the keyring lists from disappearing on us
278  * - we return -EAGAIN if we didn't find any matching key
279  * - we return -ENOKEY if we only found negative matching keys
280  * - we propagate the possession attribute from the keyring ref to the key ref
281  */
282 key_ref_t keyring_search_aux(key_ref_t keyring_ref,
283                              struct task_struct *context,
284                              struct key_type *type,
285                              const void *description,
286                              key_match_func_t match)
287 {
288         struct {
289                 struct keyring_list *keylist;
290                 int kix;
291         } stack[KEYRING_SEARCH_MAX_DEPTH];
292
293         struct keyring_list *keylist;
294         struct timespec now;
295         unsigned long possessed, kflags;
296         struct key *keyring, *key;
297         key_ref_t key_ref;
298         long err;
299         int sp, kix;
300
301         keyring = key_ref_to_ptr(keyring_ref);
302         possessed = is_key_possessed(keyring_ref);
303         key_check(keyring);
304
305         /* top keyring must have search permission to begin the search */
306         err = key_task_permission(keyring_ref, context, KEY_SEARCH);
307         if (err < 0) {
308                 key_ref = ERR_PTR(err);
309                 goto error;
310         }
311
312         key_ref = ERR_PTR(-ENOTDIR);
313         if (keyring->type != &key_type_keyring)
314                 goto error;
315
316         rcu_read_lock();
317
318         now = current_kernel_time();
319         err = -EAGAIN;
320         sp = 0;
321
322         /* firstly we should check to see if this top-level keyring is what we
323          * are looking for */
324         key_ref = ERR_PTR(-EAGAIN);
325         kflags = keyring->flags;
326         if (keyring->type == type && match(keyring, description)) {
327                 key = keyring;
328
329                 /* check it isn't negative and hasn't expired or been
330                  * revoked */
331                 if (kflags & (1 << KEY_FLAG_REVOKED))
332                         goto error_2;
333                 if (key->expiry && now.tv_sec >= key->expiry)
334                         goto error_2;
335                 key_ref = ERR_PTR(-ENOKEY);
336                 if (kflags & (1 << KEY_FLAG_NEGATIVE))
337                         goto error_2;
338                 goto found;
339         }
340
341         /* otherwise, the top keyring must not be revoked, expired, or
342          * negatively instantiated if we are to search it */
343         key_ref = ERR_PTR(-EAGAIN);
344         if (kflags & ((1 << KEY_FLAG_REVOKED) | (1 << KEY_FLAG_NEGATIVE)) ||
345             (keyring->expiry && now.tv_sec >= keyring->expiry))
346                 goto error_2;
347
348         /* start processing a new keyring */
349 descend:
350         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
351                 goto not_this_keyring;
352
353         keylist = rcu_dereference(keyring->payload.subscriptions);
354         if (!keylist)
355                 goto not_this_keyring;
356
357         /* iterate through the keys in this keyring first */
358         for (kix = 0; kix < keylist->nkeys; kix++) {
359                 key = keylist->keys[kix];
360                 kflags = key->flags;
361
362                 /* ignore keys not of this type */
363                 if (key->type != type)
364                         continue;
365
366                 /* skip revoked keys and expired keys */
367                 if (kflags & (1 << KEY_FLAG_REVOKED))
368                         continue;
369
370                 if (key->expiry && now.tv_sec >= key->expiry)
371                         continue;
372
373                 /* keys that don't match */
374                 if (!match(key, description))
375                         continue;
376
377                 /* key must have search permissions */
378                 if (key_task_permission(make_key_ref(key, possessed),
379                                         context, KEY_SEARCH) < 0)
380                         continue;
381
382                 /* we set a different error code if we pass a negative key */
383                 if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
384                         err = -ENOKEY;
385                         continue;
386                 }
387
388                 goto found;
389         }
390
391         /* search through the keyrings nested in this one */
392         kix = 0;
393 ascend:
394         for (; kix < keylist->nkeys; kix++) {
395                 key = keylist->keys[kix];
396                 if (key->type != &key_type_keyring)
397                         continue;
398
399                 /* recursively search nested keyrings
400                  * - only search keyrings for which we have search permission
401                  */
402                 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
403                         continue;
404
405                 if (key_task_permission(make_key_ref(key, possessed),
406                                         context, KEY_SEARCH) < 0)
407                         continue;
408
409                 /* stack the current position */
410                 stack[sp].keylist = keylist;
411                 stack[sp].kix = kix;
412                 sp++;
413
414                 /* begin again with the new keyring */
415                 keyring = key;
416                 goto descend;
417         }
418
419         /* the keyring we're looking at was disqualified or didn't contain a
420          * matching key */
421 not_this_keyring:
422         if (sp > 0) {
423                 /* resume the processing of a keyring higher up in the tree */
424                 sp--;
425                 keylist = stack[sp].keylist;
426                 kix = stack[sp].kix + 1;
427                 goto ascend;
428         }
429
430         key_ref = ERR_PTR(err);
431         goto error_2;
432
433         /* we found a viable match */
434 found:
435         atomic_inc(&key->usage);
436         key_check(key);
437         key_ref = make_key_ref(key, possessed);
438 error_2:
439         rcu_read_unlock();
440 error:
441         return key_ref;
442
443 } /* end keyring_search_aux() */
444
445 /*****************************************************************************/
446 /*
447  * search the supplied keyring tree for a key that matches the criterion
448  * - perform a breadth-then-depth search up to the prescribed limit
449  * - we only find keys on which we have search permission
450  * - we readlock the keyrings as we search down the tree
451  * - we return -EAGAIN if we didn't find any matching key
452  * - we return -ENOKEY if we only found negative matching keys
453  */
454 key_ref_t keyring_search(key_ref_t keyring,
455                          struct key_type *type,
456                          const char *description)
457 {
458         if (!type->match)
459                 return ERR_PTR(-ENOKEY);
460
461         return keyring_search_aux(keyring, current,
462                                   type, description, type->match);
463
464 } /* end keyring_search() */
465
466 EXPORT_SYMBOL(keyring_search);
467
468 /*****************************************************************************/
469 /*
470  * search the given keyring only (no recursion)
471  * - keyring must be locked by caller
472  * - caller must guarantee that the keyring is a keyring
473  */
474 key_ref_t __keyring_search_one(key_ref_t keyring_ref,
475                                const struct key_type *ktype,
476                                const char *description,
477                                key_perm_t perm)
478 {
479         struct keyring_list *klist;
480         unsigned long possessed;
481         struct key *keyring, *key;
482         int loop;
483
484         keyring = key_ref_to_ptr(keyring_ref);
485         possessed = is_key_possessed(keyring_ref);
486
487         rcu_read_lock();
488
489         klist = rcu_dereference(keyring->payload.subscriptions);
490         if (klist) {
491                 for (loop = 0; loop < klist->nkeys; loop++) {
492                         key = klist->keys[loop];
493
494                         if (key->type == ktype &&
495                             (!key->type->match ||
496                              key->type->match(key, description)) &&
497                             key_permission(make_key_ref(key, possessed),
498                                            perm) == 0 &&
499                             !test_bit(KEY_FLAG_REVOKED, &key->flags)
500                             )
501                                 goto found;
502                 }
503         }
504
505         rcu_read_unlock();
506         return ERR_PTR(-ENOKEY);
507
508  found:
509         atomic_inc(&key->usage);
510         rcu_read_unlock();
511         return make_key_ref(key, possessed);
512
513 } /* end __keyring_search_one() */
514
515 /*****************************************************************************/
516 /*
517  * find a keyring with the specified name
518  * - all named keyrings are searched
519  * - only find keyrings with search permission for the process
520  * - only find keyrings with a serial number greater than the one specified
521  */
522 struct key *find_keyring_by_name(const char *name, key_serial_t bound)
523 {
524         struct key *keyring;
525         int bucket;
526
527         keyring = ERR_PTR(-EINVAL);
528         if (!name)
529                 goto error;
530
531         bucket = keyring_hash(name);
532
533         read_lock(&keyring_name_lock);
534
535         if (keyring_name_hash[bucket].next) {
536                 /* search this hash bucket for a keyring with a matching name
537                  * that's readable and that hasn't been revoked */
538                 list_for_each_entry(keyring,
539                                     &keyring_name_hash[bucket],
540                                     type_data.link
541                                     ) {
542                         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
543                                 continue;
544
545                         if (strcmp(keyring->description, name) != 0)
546                                 continue;
547
548                         if (key_permission(make_key_ref(keyring, 0),
549                                            KEY_SEARCH) < 0)
550                                 continue;
551
552                         /* found a potential candidate, but we still need to
553                          * check the serial number */
554                         if (keyring->serial <= bound)
555                                 continue;
556
557                         /* we've got a match */
558                         atomic_inc(&keyring->usage);
559                         read_unlock(&keyring_name_lock);
560                         goto error;
561                 }
562         }
563
564         read_unlock(&keyring_name_lock);
565         keyring = ERR_PTR(-ENOKEY);
566
567  error:
568         return keyring;
569
570 } /* end find_keyring_by_name() */
571
572 /*****************************************************************************/
573 /*
574  * see if a cycle will will be created by inserting acyclic tree B in acyclic
575  * tree A at the topmost level (ie: as a direct child of A)
576  * - since we are adding B to A at the top level, checking for cycles should
577  *   just be a matter of seeing if node A is somewhere in tree B
578  */
579 static int keyring_detect_cycle(struct key *A, struct key *B)
580 {
581         struct {
582                 struct keyring_list *keylist;
583                 int kix;
584         } stack[KEYRING_SEARCH_MAX_DEPTH];
585
586         struct keyring_list *keylist;
587         struct key *subtree, *key;
588         int sp, kix, ret;
589
590         rcu_read_lock();
591
592         ret = -EDEADLK;
593         if (A == B)
594                 goto cycle_detected;
595
596         subtree = B;
597         sp = 0;
598
599         /* start processing a new keyring */
600  descend:
601         if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
602                 goto not_this_keyring;
603
604         keylist = rcu_dereference(subtree->payload.subscriptions);
605         if (!keylist)
606                 goto not_this_keyring;
607         kix = 0;
608
609  ascend:
610         /* iterate through the remaining keys in this keyring */
611         for (; kix < keylist->nkeys; kix++) {
612                 key = keylist->keys[kix];
613
614                 if (key == A)
615                         goto cycle_detected;
616
617                 /* recursively check nested keyrings */
618                 if (key->type == &key_type_keyring) {
619                         if (sp >= KEYRING_SEARCH_MAX_DEPTH)
620                                 goto too_deep;
621
622                         /* stack the current position */
623                         stack[sp].keylist = keylist;
624                         stack[sp].kix = kix;
625                         sp++;
626
627                         /* begin again with the new keyring */
628                         subtree = key;
629                         goto descend;
630                 }
631         }
632
633         /* the keyring we're looking at was disqualified or didn't contain a
634          * matching key */
635  not_this_keyring:
636         if (sp > 0) {
637                 /* resume the checking of a keyring higher up in the tree */
638                 sp--;
639                 keylist = stack[sp].keylist;
640                 kix = stack[sp].kix + 1;
641                 goto ascend;
642         }
643
644         ret = 0; /* no cycles detected */
645
646  error:
647         rcu_read_unlock();
648         return ret;
649
650  too_deep:
651         ret = -ELOOP;
652         goto error;
653
654  cycle_detected:
655         ret = -EDEADLK;
656         goto error;
657
658 } /* end keyring_detect_cycle() */
659
660 /*****************************************************************************/
661 /*
662  * dispose of a keyring list after the RCU grace period
663  */
664 static void keyring_link_rcu_disposal(struct rcu_head *rcu)
665 {
666         struct keyring_list *klist =
667                 container_of(rcu, struct keyring_list, rcu);
668
669         kfree(klist);
670
671 } /* end keyring_link_rcu_disposal() */
672
673 /*****************************************************************************/
674 /*
675  * dispose of a keyring list after the RCU grace period, freeing the unlinked
676  * key
677  */
678 static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
679 {
680         struct keyring_list *klist =
681                 container_of(rcu, struct keyring_list, rcu);
682
683         key_put(klist->keys[klist->delkey]);
684         kfree(klist);
685
686 } /* end keyring_unlink_rcu_disposal() */
687
688 /*****************************************************************************/
689 /*
690  * link a key into to a keyring
691  * - must be called with the keyring's semaphore write-locked
692  * - discard already extant link to matching key if there is one
693  */
694 int __key_link(struct key *keyring, struct key *key)
695 {
696         struct keyring_list *klist, *nklist;
697         unsigned max;
698         size_t size;
699         int loop, ret;
700
701         ret = -EKEYREVOKED;
702         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
703                 goto error;
704
705         ret = -ENOTDIR;
706         if (keyring->type != &key_type_keyring)
707                 goto error;
708
709         /* serialise link/link calls to prevent parallel calls causing a
710          * cycle when applied to two keyring in opposite orders */
711         down_write(&keyring_serialise_link_sem);
712
713         /* check that we aren't going to create a cycle adding one keyring to
714          * another */
715         if (key->type == &key_type_keyring) {
716                 ret = keyring_detect_cycle(keyring, key);
717                 if (ret < 0)
718                         goto error2;
719         }
720
721         /* see if there's a matching key we can displace */
722         klist = keyring->payload.subscriptions;
723
724         if (klist && klist->nkeys > 0) {
725                 struct key_type *type = key->type;
726
727                 for (loop = klist->nkeys - 1; loop >= 0; loop--) {
728                         if (klist->keys[loop]->type == type &&
729                             strcmp(klist->keys[loop]->description,
730                                    key->description) == 0
731                             ) {
732                                 /* found a match - replace with new key */
733                                 size = sizeof(struct key *) * klist->maxkeys;
734                                 size += sizeof(*klist);
735                                 BUG_ON(size > PAGE_SIZE);
736
737                                 ret = -ENOMEM;
738                                 nklist = kmemdup(klist, size, GFP_KERNEL);
739                                 if (!nklist)
740                                         goto error2;
741
742                                 /* replace matched key */
743                                 atomic_inc(&key->usage);
744                                 nklist->keys[loop] = key;
745
746                                 rcu_assign_pointer(
747                                         keyring->payload.subscriptions,
748                                         nklist);
749
750                                 /* dispose of the old keyring list and the
751                                  * displaced key */
752                                 klist->delkey = loop;
753                                 call_rcu(&klist->rcu,
754                                          keyring_unlink_rcu_disposal);
755
756                                 goto done;
757                         }
758                 }
759         }
760
761         /* check that we aren't going to overrun the user's quota */
762         ret = key_payload_reserve(keyring,
763                                   keyring->datalen + KEYQUOTA_LINK_BYTES);
764         if (ret < 0)
765                 goto error2;
766
767         klist = keyring->payload.subscriptions;
768
769         if (klist && klist->nkeys < klist->maxkeys) {
770                 /* there's sufficient slack space to add directly */
771                 atomic_inc(&key->usage);
772
773                 klist->keys[klist->nkeys] = key;
774                 smp_wmb();
775                 klist->nkeys++;
776                 smp_wmb();
777         }
778         else {
779                 /* grow the key list */
780                 max = 4;
781                 if (klist)
782                         max += klist->maxkeys;
783
784                 ret = -ENFILE;
785                 if (max > 65535)
786                         goto error3;
787                 size = sizeof(*klist) + sizeof(struct key *) * max;
788                 if (size > PAGE_SIZE)
789                         goto error3;
790
791                 ret = -ENOMEM;
792                 nklist = kmalloc(size, GFP_KERNEL);
793                 if (!nklist)
794                         goto error3;
795                 nklist->maxkeys = max;
796                 nklist->nkeys = 0;
797
798                 if (klist) {
799                         nklist->nkeys = klist->nkeys;
800                         memcpy(nklist->keys,
801                                klist->keys,
802                                sizeof(struct key *) * klist->nkeys);
803                 }
804
805                 /* add the key into the new space */
806                 atomic_inc(&key->usage);
807                 nklist->keys[nklist->nkeys++] = key;
808
809                 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
810
811                 /* dispose of the old keyring list */
812                 if (klist)
813                         call_rcu(&klist->rcu, keyring_link_rcu_disposal);
814         }
815
816 done:
817         ret = 0;
818 error2:
819         up_write(&keyring_serialise_link_sem);
820 error:
821         return ret;
822
823 error3:
824         /* undo the quota changes */
825         key_payload_reserve(keyring,
826                             keyring->datalen - KEYQUOTA_LINK_BYTES);
827         goto error2;
828
829 } /* end __key_link() */
830
831 /*****************************************************************************/
832 /*
833  * link a key to a keyring
834  */
835 int key_link(struct key *keyring, struct key *key)
836 {
837         int ret;
838
839         key_check(keyring);
840         key_check(key);
841
842         down_write(&keyring->sem);
843         ret = __key_link(keyring, key);
844         up_write(&keyring->sem);
845
846         return ret;
847
848 } /* end key_link() */
849
850 EXPORT_SYMBOL(key_link);
851
852 /*****************************************************************************/
853 /*
854  * unlink the first link to a key from a keyring
855  */
856 int key_unlink(struct key *keyring, struct key *key)
857 {
858         struct keyring_list *klist, *nklist;
859         int loop, ret;
860
861         key_check(keyring);
862         key_check(key);
863
864         ret = -ENOTDIR;
865         if (keyring->type != &key_type_keyring)
866                 goto error;
867
868         down_write(&keyring->sem);
869
870         klist = keyring->payload.subscriptions;
871         if (klist) {
872                 /* search the keyring for the key */
873                 for (loop = 0; loop < klist->nkeys; loop++)
874                         if (klist->keys[loop] == key)
875                                 goto key_is_present;
876         }
877
878         up_write(&keyring->sem);
879         ret = -ENOENT;
880         goto error;
881
882 key_is_present:
883         /* we need to copy the key list for RCU purposes */
884         nklist = kmalloc(sizeof(*klist) +
885                          sizeof(struct key *) * klist->maxkeys,
886                          GFP_KERNEL);
887         if (!nklist)
888                 goto nomem;
889         nklist->maxkeys = klist->maxkeys;
890         nklist->nkeys = klist->nkeys - 1;
891
892         if (loop > 0)
893                 memcpy(&nklist->keys[0],
894                        &klist->keys[0],
895                        loop * sizeof(struct key *));
896
897         if (loop < nklist->nkeys)
898                 memcpy(&nklist->keys[loop],
899                        &klist->keys[loop + 1],
900                        (nklist->nkeys - loop) * sizeof(struct key *));
901
902         /* adjust the user's quota */
903         key_payload_reserve(keyring,
904                             keyring->datalen - KEYQUOTA_LINK_BYTES);
905
906         rcu_assign_pointer(keyring->payload.subscriptions, nklist);
907
908         up_write(&keyring->sem);
909
910         /* schedule for later cleanup */
911         klist->delkey = loop;
912         call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
913
914         ret = 0;
915
916 error:
917         return ret;
918 nomem:
919         ret = -ENOMEM;
920         up_write(&keyring->sem);
921         goto error;
922
923 } /* end key_unlink() */
924
925 EXPORT_SYMBOL(key_unlink);
926
927 /*****************************************************************************/
928 /*
929  * dispose of a keyring list after the RCU grace period, releasing the keys it
930  * links to
931  */
932 static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
933 {
934         struct keyring_list *klist;
935         int loop;
936
937         klist = container_of(rcu, struct keyring_list, rcu);
938
939         for (loop = klist->nkeys - 1; loop >= 0; loop--)
940                 key_put(klist->keys[loop]);
941
942         kfree(klist);
943
944 } /* end keyring_clear_rcu_disposal() */
945
946 /*****************************************************************************/
947 /*
948  * clear the specified process keyring
949  * - implements keyctl(KEYCTL_CLEAR)
950  */
951 int keyring_clear(struct key *keyring)
952 {
953         struct keyring_list *klist;
954         int ret;
955
956         ret = -ENOTDIR;
957         if (keyring->type == &key_type_keyring) {
958                 /* detach the pointer block with the locks held */
959                 down_write(&keyring->sem);
960
961                 klist = keyring->payload.subscriptions;
962                 if (klist) {
963                         /* adjust the quota */
964                         key_payload_reserve(keyring,
965                                             sizeof(struct keyring_list));
966
967                         rcu_assign_pointer(keyring->payload.subscriptions,
968                                            NULL);
969                 }
970
971                 up_write(&keyring->sem);
972
973                 /* free the keys after the locks have been dropped */
974                 if (klist)
975                         call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
976
977                 ret = 0;
978         }
979
980         return ret;
981
982 } /* end keyring_clear() */
983
984 EXPORT_SYMBOL(keyring_clear);
985
986 /*****************************************************************************/
987 /*
988  * dispose of the links from a revoked keyring
989  * - called with the key sem write-locked
990  */
991 static void keyring_revoke(struct key *keyring)
992 {
993         struct keyring_list *klist = keyring->payload.subscriptions;
994
995         /* adjust the quota */
996         key_payload_reserve(keyring, 0);
997
998         if (klist) {
999                 rcu_assign_pointer(keyring->payload.subscriptions, NULL);
1000                 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
1001         }
1002
1003 } /* end keyring_revoke() */