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;
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 /* start processing a new keyring */
323 descend:
324 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
325 goto not_this_keyring;
326
327 keylist = rcu_dereference(keyring->payload.subscriptions);
328 if (!keylist)
329 goto not_this_keyring;
330
331 /* iterate through the keys in this keyring first */
332 for (kix = 0; kix < keylist->nkeys; kix++) {
333 key = keylist->keys[kix];
334
335 /* ignore keys not of this type */
336 if (key->type != type)
337 continue;
338
339 /* skip revoked keys and expired keys */
340 if (test_bit(KEY_FLAG_REVOKED, &key->flags))
341 continue;
342
343 if (key->expiry && now.tv_sec >= key->expiry)
344 continue;
345
346 /* keys that don't match */
347 if (!match(key, description))
348 continue;
349
350 /* key must have search permissions */
351 if (key_task_permission(make_key_ref(key, possessed),
352 context, KEY_SEARCH) < 0)
353 continue;
354
355 /* we set a different error code if we find a negative key */
356 if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
357 err = -ENOKEY;
358 continue;
359 }
360
361 goto found;
362 }
363
364 /* search through the keyrings nested in this one */
365 kix = 0;
366 ascend:
367 for (; kix < keylist->nkeys; kix++) {
368 key = keylist->keys[kix];
369 if (key->type != &key_type_keyring)
370 continue;
371
372 /* recursively search nested keyrings
373 * - only search keyrings for which we have search permission
374 */
375 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
376 continue;
377
378 if (key_task_permission(make_key_ref(key, possessed),
379 context, KEY_SEARCH) < 0)
380 continue;
381
382 /* stack the current position */
383 stack[sp].keylist = keylist;
384 stack[sp].kix = kix;
385 sp++;
386
387 /* begin again with the new keyring */
388 keyring = key;
389 goto descend;
390 }
391
392 /* the keyring we're looking at was disqualified or didn't contain a
393 * matching key */
394 not_this_keyring:
395 if (sp > 0) {
396 /* resume the processing of a keyring higher up in the tree */
397 sp--;
398 keylist = stack[sp].keylist;
399 kix = stack[sp].kix + 1;
400 goto ascend;
401 }
402
403 key_ref = ERR_PTR(err);
404 goto error_2;
405
406 /* we found a viable match */
407 found:
408 atomic_inc(&key->usage);
409 key_check(key);
410 key_ref = make_key_ref(key, possessed);
411 error_2:
412 rcu_read_unlock();
413 error:
414 return key_ref;
415
416 } /* end keyring_search_aux() */
417
418 /*****************************************************************************/
419 /*
420 * search the supplied keyring tree for a key that matches the criterion
421 * - perform a breadth-then-depth search up to the prescribed limit
422 * - we only find keys on which we have search permission
423 * - we readlock the keyrings as we search down the tree
424 * - we return -EAGAIN if we didn't find any matching key
425 * - we return -ENOKEY if we only found negative matching keys
426 */
427 key_ref_t keyring_search(key_ref_t keyring,
428 struct key_type *type,
429 const char *description)
430 {
431 if (!type->match)
432 return ERR_PTR(-ENOKEY);
433
434 return keyring_search_aux(keyring, current,
435 type, description, type->match);
436
437 } /* end keyring_search() */
438
439 EXPORT_SYMBOL(keyring_search);
440
441 /*****************************************************************************/
442 /*
443 * search the given keyring only (no recursion)
444 * - keyring must be locked by caller
445 * - caller must guarantee that the keyring is a keyring
446 */
447 key_ref_t __keyring_search_one(key_ref_t keyring_ref,
448 const struct key_type *ktype,
449 const char *description,
450 key_perm_t perm)
451 {
452 struct keyring_list *klist;
453 unsigned long possessed;
454 struct key *keyring, *key;
455 int loop;
456
457 keyring = key_ref_to_ptr(keyring_ref);
458 possessed = is_key_possessed(keyring_ref);
459
460 rcu_read_lock();
461
462 klist = rcu_dereference(keyring->payload.subscriptions);
463 if (klist) {
464 for (loop = 0; loop < klist->nkeys; loop++) {
465 key = klist->keys[loop];
466
467 if (key->type == ktype &&
468 (!key->type->match ||
469 key->type->match(key, description)) &&
470 key_permission(make_key_ref(key, possessed),
471 perm) == 0 &&
472 !test_bit(KEY_FLAG_REVOKED, &key->flags)
473 )
474 goto found;
475 }
476 }
477
478 rcu_read_unlock();
479 return ERR_PTR(-ENOKEY);
480
481 found:
482 atomic_inc(&key->usage);
483 rcu_read_unlock();
484 return make_key_ref(key, possessed);
485
486 } /* end __keyring_search_one() */
487
488 /*****************************************************************************/
489 /*
490 * find a keyring with the specified name
491 * - all named keyrings are searched
492 * - only find keyrings with search permission for the process
493 * - only find keyrings with a serial number greater than the one specified
494 */
495 struct key *find_keyring_by_name(const char *name, key_serial_t bound)
496 {
497 struct key *keyring;
498 int bucket;
499
500 keyring = ERR_PTR(-EINVAL);
501 if (!name)
502 goto error;
503
504 bucket = keyring_hash(name);
505
506 read_lock(&keyring_name_lock);
507
508 if (keyring_name_hash[bucket].next) {
509 /* search this hash bucket for a keyring with a matching name
510 * that's readable and that hasn't been revoked */
511 list_for_each_entry(keyring,
512 &keyring_name_hash[bucket],
513 type_data.link
514 ) {
515 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
516 continue;
517
518 if (strcmp(keyring->description, name) != 0)
519 continue;
520
521 if (key_permission(make_key_ref(keyring, 0),
522 KEY_SEARCH) < 0)
523 continue;
524
525 /* found a potential candidate, but we still need to
526 * check the serial number */
527 if (keyring->serial <= bound)
528 continue;
529
530 /* we've got a match */
531 atomic_inc(&keyring->usage);
532 read_unlock(&keyring_name_lock);
533 goto error;
534 }
535 }
536
537 read_unlock(&keyring_name_lock);
538 keyring = ERR_PTR(-ENOKEY);
539
540 error:
541 return keyring;
542
543 } /* end find_keyring_by_name() */
544
545 /*****************************************************************************/
546 /*
547 * see if a cycle will will be created by inserting acyclic tree B in acyclic
548 * tree A at the topmost level (ie: as a direct child of A)
549 * - since we are adding B to A at the top level, checking for cycles should
550 * just be a matter of seeing if node A is somewhere in tree B
551 */
552 static int keyring_detect_cycle(struct key *A, struct key *B)
553 {
554 struct {
555 struct keyring_list *keylist;
556 int kix;
557 } stack[KEYRING_SEARCH_MAX_DEPTH];
558
559 struct keyring_list *keylist;
560 struct key *subtree, *key;
561 int sp, kix, ret;
562
563 rcu_read_lock();
564
565 ret = -EDEADLK;
566 if (A == B)
567 goto cycle_detected;
568
569 subtree = B;
570 sp = 0;
571
572 /* start processing a new keyring */
573 descend:
574 if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
575 goto not_this_keyring;
576
577 keylist = rcu_dereference(subtree->payload.subscriptions);
578 if (!keylist)
579 goto not_this_keyring;
580 kix = 0;
581
582 ascend:
583 /* iterate through the remaining keys in this keyring */
584 for (; kix < keylist->nkeys; kix++) {
585 key = keylist->keys[kix];
586
587 if (key == A)
588 goto cycle_detected;
589
590 /* recursively check nested keyrings */
591 if (key->type == &key_type_keyring) {
592 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
593 goto too_deep;
594
595 /* stack the current position */
596 stack[sp].keylist = keylist;
597 stack[sp].kix = kix;
598 sp++;
599
600 /* begin again with the new keyring */
601 subtree = key;
602 goto descend;
603 }
604 }
605
606 /* the keyring we're looking at was disqualified or didn't contain a
607 * matching key */
608 not_this_keyring:
609 if (sp > 0) {
610 /* resume the checking of a keyring higher up in the tree */
611 sp--;
612 keylist = stack[sp].keylist;
613 kix = stack[sp].kix + 1;
614 goto ascend;
615 }
616
617 ret = 0; /* no cycles detected */
618
619 error:
620 rcu_read_unlock();
621 return ret;
622
623 too_deep:
624 ret = -ELOOP;
625 goto error;
626
627 cycle_detected:
628 ret = -EDEADLK;
629 goto error;
630
631 } /* end keyring_detect_cycle() */
632
633 /*****************************************************************************/
634 /*
635 * dispose of a keyring list after the RCU grace period
636 */
637 static void keyring_link_rcu_disposal(struct rcu_head *rcu)
638 {
639 struct keyring_list *klist =
640 container_of(rcu, struct keyring_list, rcu);
641
642 kfree(klist);
643
644 } /* end keyring_link_rcu_disposal() */
645
646 /*****************************************************************************/
647 /*
648 * dispose of a keyring list after the RCU grace period, freeing the unlinked
649 * key
650 */
651 static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
652 {
653 struct keyring_list *klist =
654 container_of(rcu, struct keyring_list, rcu);
655
656 key_put(klist->keys[klist->delkey]);
657 kfree(klist);
658
659 } /* end keyring_unlink_rcu_disposal() */
660
661 /*****************************************************************************/
662 /*
663 * link a key into to a keyring
664 * - must be called with the keyring's semaphore write-locked
665 * - discard already extant link to matching key if there is one
666 */
667 int __key_link(struct key *keyring, struct key *key)
668 {
669 struct keyring_list *klist, *nklist;
670 unsigned max;
671 size_t size;
672 int loop, ret;
673
674 ret = -EKEYREVOKED;
675 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
676 goto error;
677
678 ret = -ENOTDIR;
679 if (keyring->type != &key_type_keyring)
680 goto error;
681
682 /* serialise link/link calls to prevent parallel calls causing a
683 * cycle when applied to two keyring in opposite orders */
684 down_write(&keyring_serialise_link_sem);
685
686 /* check that we aren't going to create a cycle adding one keyring to
687 * another */
688 if (key->type == &key_type_keyring) {
689 ret = keyring_detect_cycle(keyring, key);
690 if (ret < 0)
691 goto error2;
692 }
693
694 /* see if there's a matching key we can displace */
695 klist = keyring->payload.subscriptions;
696
697 if (klist && klist->nkeys > 0) {
698 struct key_type *type = key->type;
699
700 for (loop = klist->nkeys - 1; loop >= 0; loop--) {
701 if (klist->keys[loop]->type == type &&
702 strcmp(klist->keys[loop]->description,
703 key->description) == 0
704 ) {
705 /* found a match - replace with new key */
706 size = sizeof(struct key *) * klist->maxkeys;
707 size += sizeof(*klist);
708 BUG_ON(size > PAGE_SIZE);
709
710 ret = -ENOMEM;
711 nklist = kmemdup(klist, size, GFP_KERNEL);
712 if (!nklist)
713 goto error2;
714
715 /* replace matched key */
716 atomic_inc(&key->usage);
717 nklist->keys[loop] = key;
718
719 rcu_assign_pointer(
720 keyring->payload.subscriptions,
721 nklist);
722
723 /* dispose of the old keyring list and the
724 * displaced key */
725 klist->delkey = loop;
726 call_rcu(&klist->rcu,
727 keyring_unlink_rcu_disposal);
728
729 goto done;
730 }
731 }
732 }
733
734 /* check that we aren't going to overrun the user's quota */
735 ret = key_payload_reserve(keyring,
736 keyring->datalen + KEYQUOTA_LINK_BYTES);
737 if (ret < 0)
738 goto error2;
739
740 klist = keyring->payload.subscriptions;
741
742 if (klist && klist->nkeys < klist->maxkeys) {
743 /* there's sufficient slack space to add directly */
744 atomic_inc(&key->usage);
745
746 klist->keys[klist->nkeys] = key;
747 smp_wmb();
748 klist->nkeys++;
749 smp_wmb();
750 }
751 else {
752 /* grow the key list */
753 max = 4;
754 if (klist)
755 max += klist->maxkeys;
756
757 ret = -ENFILE;
758 if (max > 65535)
759 goto error3;
760 size = sizeof(*klist) + sizeof(struct key *) * max;
761 if (size > PAGE_SIZE)
762 goto error3;
763
764 ret = -ENOMEM;
765 nklist = kmalloc(size, GFP_KERNEL);
766 if (!nklist)
767 goto error3;
768 nklist->maxkeys = max;
769 nklist->nkeys = 0;
770
771 if (klist) {
772 nklist->nkeys = klist->nkeys;
773 memcpy(nklist->keys,
774 klist->keys,
775 sizeof(struct key *) * klist->nkeys);
776 }
777
778 /* add the key into the new space */
779 atomic_inc(&key->usage);
780 nklist->keys[nklist->nkeys++] = key;
781
782 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
783
784 /* dispose of the old keyring list */
785 if (klist)
786 call_rcu(&klist->rcu, keyring_link_rcu_disposal);
787 }
788
789 done:
790 ret = 0;
791 error2:
792 up_write(&keyring_serialise_link_sem);
793 error:
794 return ret;
795
796 error3:
797 /* undo the quota changes */
798 key_payload_reserve(keyring,
799 keyring->datalen - KEYQUOTA_LINK_BYTES);
800 goto error2;
801
802 } /* end __key_link() */
803
804 /*****************************************************************************/
805 /*
806 * link a key to a keyring
807 */
808 int key_link(struct key *keyring, struct key *key)
809 {
810 int ret;
811
812 key_check(keyring);
813 key_check(key);
814
815 down_write(&keyring->sem);
816 ret = __key_link(keyring, key);
817 up_write(&keyring->sem);
818
819 return ret;
820
821 } /* end key_link() */
822
823 EXPORT_SYMBOL(key_link);
824
825 /*****************************************************************************/
826 /*
827 * unlink the first link to a key from a keyring
828 */
829 int key_unlink(struct key *keyring, struct key *key)
830 {
831 struct keyring_list *klist, *nklist;
832 int loop, ret;
833
834 key_check(keyring);
835 key_check(key);
836
837 ret = -ENOTDIR;
838 if (keyring->type != &key_type_keyring)
839 goto error;
840
841 down_write(&keyring->sem);
842
843 klist = keyring->payload.subscriptions;
844 if (klist) {
845 /* search the keyring for the key */
846 for (loop = 0; loop < klist->nkeys; loop++)
847 if (klist->keys[loop] == key)
848 goto key_is_present;
849 }
850
851 up_write(&keyring->sem);
852 ret = -ENOENT;
853 goto error;
854
855 key_is_present:
856 /* we need to copy the key list for RCU purposes */
857 nklist = kmalloc(sizeof(*klist) +
858 sizeof(struct key *) * klist->maxkeys,
859 GFP_KERNEL);
860 if (!nklist)
861 goto nomem;
862 nklist->maxkeys = klist->maxkeys;
863 nklist->nkeys = klist->nkeys - 1;
864
865 if (loop > 0)
866 memcpy(&nklist->keys[0],
867 &klist->keys[0],
868 loop * sizeof(struct key *));
869
870 if (loop < nklist->nkeys)
871 memcpy(&nklist->keys[loop],
872 &klist->keys[loop + 1],
873 (nklist->nkeys - loop) * sizeof(struct key *));
874
875 /* adjust the user's quota */
876 key_payload_reserve(keyring,
877 keyring->datalen - KEYQUOTA_LINK_BYTES);
878
879 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
880
881 up_write(&keyring->sem);
882
883 /* schedule for later cleanup */
884 klist->delkey = loop;
885 call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
886
887 ret = 0;
888
889 error:
890 return ret;
891 nomem:
892 ret = -ENOMEM;
893 up_write(&keyring->sem);
894 goto error;
895
896 } /* end key_unlink() */
897
898 EXPORT_SYMBOL(key_unlink);
899
900 /*****************************************************************************/
901 /*
902 * dispose of a keyring list after the RCU grace period, releasing the keys it
903 * links to
904 */
905 static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
906 {
907 struct keyring_list *klist;
908 int loop;
909
910 klist = container_of(rcu, struct keyring_list, rcu);
911
912 for (loop = klist->nkeys - 1; loop >= 0; loop--)
913 key_put(klist->keys[loop]);
914
915 kfree(klist);
916
917 } /* end keyring_clear_rcu_disposal() */
918
919 /*****************************************************************************/
920 /*
921 * clear the specified process keyring
922 * - implements keyctl(KEYCTL_CLEAR)
923 */
924 int keyring_clear(struct key *keyring)
925 {
926 struct keyring_list *klist;
927 int ret;
928
929 ret = -ENOTDIR;
930 if (keyring->type == &key_type_keyring) {
931 /* detach the pointer block with the locks held */
932 down_write(&keyring->sem);
933
934 klist = keyring->payload.subscriptions;
935 if (klist) {
936 /* adjust the quota */
937 key_payload_reserve(keyring,
938 sizeof(struct keyring_list));
939
940 rcu_assign_pointer(keyring->payload.subscriptions,
941 NULL);
942 }
943
944 up_write(&keyring->sem);
945
946 /* free the keys after the locks have been dropped */
947 if (klist)
948 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
949
950 ret = 0;
951 }
952
953 return ret;
954
955 } /* end keyring_clear() */
956
957 EXPORT_SYMBOL(keyring_clear);
958
959 /*****************************************************************************/
960 /*
961 * dispose of the links from a revoked keyring
962 * - called with the key sem write-locked
963 */
964 static void keyring_revoke(struct key *keyring)
965 {
966 struct keyring_list *klist = keyring->payload.subscriptions;
967
968 /* adjust the quota */
969 key_payload_reserve(keyring, 0);
970
971 if (klist) {
972 rcu_assign_pointer(keyring->payload.subscriptions, NULL);
973 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
974 }
975
976 } /* end keyring_revoke() */
977
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