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Linux/security/keys/keyring.c

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  1 /* Keyring handling
  2  *
  3  * Copyright (C) 2004-2005, 2008, 2013 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 <keys/keyring-type.h>
 20 #include <keys/user-type.h>
 21 #include <linux/assoc_array_priv.h>
 22 #include <linux/uaccess.h>
 23 #include "internal.h"
 24 
 25 /*
 26  * When plumbing the depths of the key tree, this sets a hard limit
 27  * set on how deep we're willing to go.
 28  */
 29 #define KEYRING_SEARCH_MAX_DEPTH 6
 30 
 31 /*
 32  * We keep all named keyrings in a hash to speed looking them up.
 33  */
 34 #define KEYRING_NAME_HASH_SIZE  (1 << 5)
 35 
 36 /*
 37  * We mark pointers we pass to the associative array with bit 1 set if
 38  * they're keyrings and clear otherwise.
 39  */
 40 #define KEYRING_PTR_SUBTYPE     0x2UL
 41 
 42 static inline bool keyring_ptr_is_keyring(const struct assoc_array_ptr *x)
 43 {
 44         return (unsigned long)x & KEYRING_PTR_SUBTYPE;
 45 }
 46 static inline struct key *keyring_ptr_to_key(const struct assoc_array_ptr *x)
 47 {
 48         void *object = assoc_array_ptr_to_leaf(x);
 49         return (struct key *)((unsigned long)object & ~KEYRING_PTR_SUBTYPE);
 50 }
 51 static inline void *keyring_key_to_ptr(struct key *key)
 52 {
 53         if (key->type == &key_type_keyring)
 54                 return (void *)((unsigned long)key | KEYRING_PTR_SUBTYPE);
 55         return key;
 56 }
 57 
 58 static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
 59 static DEFINE_RWLOCK(keyring_name_lock);
 60 
 61 static inline unsigned keyring_hash(const char *desc)
 62 {
 63         unsigned bucket = 0;
 64 
 65         for (; *desc; desc++)
 66                 bucket += (unsigned char)*desc;
 67 
 68         return bucket & (KEYRING_NAME_HASH_SIZE - 1);
 69 }
 70 
 71 /*
 72  * The keyring key type definition.  Keyrings are simply keys of this type and
 73  * can be treated as ordinary keys in addition to having their own special
 74  * operations.
 75  */
 76 static int keyring_preparse(struct key_preparsed_payload *prep);
 77 static void keyring_free_preparse(struct key_preparsed_payload *prep);
 78 static int keyring_instantiate(struct key *keyring,
 79                                struct key_preparsed_payload *prep);
 80 static void keyring_revoke(struct key *keyring);
 81 static void keyring_destroy(struct key *keyring);
 82 static void keyring_describe(const struct key *keyring, struct seq_file *m);
 83 static long keyring_read(const struct key *keyring,
 84                          char __user *buffer, size_t buflen);
 85 
 86 struct key_type key_type_keyring = {
 87         .name           = "keyring",
 88         .def_datalen    = 0,
 89         .preparse       = keyring_preparse,
 90         .free_preparse  = keyring_free_preparse,
 91         .instantiate    = keyring_instantiate,
 92         .revoke         = keyring_revoke,
 93         .destroy        = keyring_destroy,
 94         .describe       = keyring_describe,
 95         .read           = keyring_read,
 96 };
 97 EXPORT_SYMBOL(key_type_keyring);
 98 
 99 /*
100  * Semaphore to serialise link/link calls to prevent two link calls in parallel
101  * introducing a cycle.
102  */
103 static DECLARE_RWSEM(keyring_serialise_link_sem);
104 
105 /*
106  * Publish the name of a keyring so that it can be found by name (if it has
107  * one).
108  */
109 static void keyring_publish_name(struct key *keyring)
110 {
111         int bucket;
112 
113         if (keyring->description) {
114                 bucket = keyring_hash(keyring->description);
115 
116                 write_lock(&keyring_name_lock);
117 
118                 if (!keyring_name_hash[bucket].next)
119                         INIT_LIST_HEAD(&keyring_name_hash[bucket]);
120 
121                 list_add_tail(&keyring->type_data.link,
122                               &keyring_name_hash[bucket]);
123 
124                 write_unlock(&keyring_name_lock);
125         }
126 }
127 
128 /*
129  * Preparse a keyring payload
130  */
131 static int keyring_preparse(struct key_preparsed_payload *prep)
132 {
133         return prep->datalen != 0 ? -EINVAL : 0;
134 }
135 
136 /*
137  * Free a preparse of a user defined key payload
138  */
139 static void keyring_free_preparse(struct key_preparsed_payload *prep)
140 {
141 }
142 
143 /*
144  * Initialise a keyring.
145  *
146  * Returns 0 on success, -EINVAL if given any data.
147  */
148 static int keyring_instantiate(struct key *keyring,
149                                struct key_preparsed_payload *prep)
150 {
151         assoc_array_init(&keyring->keys);
152         /* make the keyring available by name if it has one */
153         keyring_publish_name(keyring);
154         return 0;
155 }
156 
157 /*
158  * Multiply 64-bits by 32-bits to 96-bits and fold back to 64-bit.  Ideally we'd
159  * fold the carry back too, but that requires inline asm.
160  */
161 static u64 mult_64x32_and_fold(u64 x, u32 y)
162 {
163         u64 hi = (u64)(u32)(x >> 32) * y;
164         u64 lo = (u64)(u32)(x) * y;
165         return lo + ((u64)(u32)hi << 32) + (u32)(hi >> 32);
166 }
167 
168 /*
169  * Hash a key type and description.
170  */
171 static unsigned long hash_key_type_and_desc(const struct keyring_index_key *index_key)
172 {
173         const unsigned level_shift = ASSOC_ARRAY_LEVEL_STEP;
174         const unsigned long fan_mask = ASSOC_ARRAY_FAN_MASK;
175         const char *description = index_key->description;
176         unsigned long hash, type;
177         u32 piece;
178         u64 acc;
179         int n, desc_len = index_key->desc_len;
180 
181         type = (unsigned long)index_key->type;
182 
183         acc = mult_64x32_and_fold(type, desc_len + 13);
184         acc = mult_64x32_and_fold(acc, 9207);
185         for (;;) {
186                 n = desc_len;
187                 if (n <= 0)
188                         break;
189                 if (n > 4)
190                         n = 4;
191                 piece = 0;
192                 memcpy(&piece, description, n);
193                 description += n;
194                 desc_len -= n;
195                 acc = mult_64x32_and_fold(acc, piece);
196                 acc = mult_64x32_and_fold(acc, 9207);
197         }
198 
199         /* Fold the hash down to 32 bits if need be. */
200         hash = acc;
201         if (ASSOC_ARRAY_KEY_CHUNK_SIZE == 32)
202                 hash ^= acc >> 32;
203 
204         /* Squidge all the keyrings into a separate part of the tree to
205          * ordinary keys by making sure the lowest level segment in the hash is
206          * zero for keyrings and non-zero otherwise.
207          */
208         if (index_key->type != &key_type_keyring && (hash & fan_mask) == 0)
209                 return hash | (hash >> (ASSOC_ARRAY_KEY_CHUNK_SIZE - level_shift)) | 1;
210         if (index_key->type == &key_type_keyring && (hash & fan_mask) != 0)
211                 return (hash + (hash << level_shift)) & ~fan_mask;
212         return hash;
213 }
214 
215 /*
216  * Build the next index key chunk.
217  *
218  * On 32-bit systems the index key is laid out as:
219  *
220  *      0       4       5       9...
221  *      hash    desclen typeptr desc[]
222  *
223  * On 64-bit systems:
224  *
225  *      0       8       9       17...
226  *      hash    desclen typeptr desc[]
227  *
228  * We return it one word-sized chunk at a time.
229  */
230 static unsigned long keyring_get_key_chunk(const void *data, int level)
231 {
232         const struct keyring_index_key *index_key = data;
233         unsigned long chunk = 0;
234         long offset = 0;
235         int desc_len = index_key->desc_len, n = sizeof(chunk);
236 
237         level /= ASSOC_ARRAY_KEY_CHUNK_SIZE;
238         switch (level) {
239         case 0:
240                 return hash_key_type_and_desc(index_key);
241         case 1:
242                 return ((unsigned long)index_key->type << 8) | desc_len;
243         case 2:
244                 if (desc_len == 0)
245                         return (u8)((unsigned long)index_key->type >>
246                                     (ASSOC_ARRAY_KEY_CHUNK_SIZE - 8));
247                 n--;
248                 offset = 1;
249         default:
250                 offset += sizeof(chunk) - 1;
251                 offset += (level - 3) * sizeof(chunk);
252                 if (offset >= desc_len)
253                         return 0;
254                 desc_len -= offset;
255                 if (desc_len > n)
256                         desc_len = n;
257                 offset += desc_len;
258                 do {
259                         chunk <<= 8;
260                         chunk |= ((u8*)index_key->description)[--offset];
261                 } while (--desc_len > 0);
262 
263                 if (level == 2) {
264                         chunk <<= 8;
265                         chunk |= (u8)((unsigned long)index_key->type >>
266                                       (ASSOC_ARRAY_KEY_CHUNK_SIZE - 8));
267                 }
268                 return chunk;
269         }
270 }
271 
272 static unsigned long keyring_get_object_key_chunk(const void *object, int level)
273 {
274         const struct key *key = keyring_ptr_to_key(object);
275         return keyring_get_key_chunk(&key->index_key, level);
276 }
277 
278 static bool keyring_compare_object(const void *object, const void *data)
279 {
280         const struct keyring_index_key *index_key = data;
281         const struct key *key = keyring_ptr_to_key(object);
282 
283         return key->index_key.type == index_key->type &&
284                 key->index_key.desc_len == index_key->desc_len &&
285                 memcmp(key->index_key.description, index_key->description,
286                        index_key->desc_len) == 0;
287 }
288 
289 /*
290  * Compare the index keys of a pair of objects and determine the bit position
291  * at which they differ - if they differ.
292  */
293 static int keyring_diff_objects(const void *object, const void *data)
294 {
295         const struct key *key_a = keyring_ptr_to_key(object);
296         const struct keyring_index_key *a = &key_a->index_key;
297         const struct keyring_index_key *b = data;
298         unsigned long seg_a, seg_b;
299         int level, i;
300 
301         level = 0;
302         seg_a = hash_key_type_and_desc(a);
303         seg_b = hash_key_type_and_desc(b);
304         if ((seg_a ^ seg_b) != 0)
305                 goto differ;
306 
307         /* The number of bits contributed by the hash is controlled by a
308          * constant in the assoc_array headers.  Everything else thereafter we
309          * can deal with as being machine word-size dependent.
310          */
311         level += ASSOC_ARRAY_KEY_CHUNK_SIZE / 8;
312         seg_a = a->desc_len;
313         seg_b = b->desc_len;
314         if ((seg_a ^ seg_b) != 0)
315                 goto differ;
316 
317         /* The next bit may not work on big endian */
318         level++;
319         seg_a = (unsigned long)a->type;
320         seg_b = (unsigned long)b->type;
321         if ((seg_a ^ seg_b) != 0)
322                 goto differ;
323 
324         level += sizeof(unsigned long);
325         if (a->desc_len == 0)
326                 goto same;
327 
328         i = 0;
329         if (((unsigned long)a->description | (unsigned long)b->description) &
330             (sizeof(unsigned long) - 1)) {
331                 do {
332                         seg_a = *(unsigned long *)(a->description + i);
333                         seg_b = *(unsigned long *)(b->description + i);
334                         if ((seg_a ^ seg_b) != 0)
335                                 goto differ_plus_i;
336                         i += sizeof(unsigned long);
337                 } while (i < (a->desc_len & (sizeof(unsigned long) - 1)));
338         }
339 
340         for (; i < a->desc_len; i++) {
341                 seg_a = *(unsigned char *)(a->description + i);
342                 seg_b = *(unsigned char *)(b->description + i);
343                 if ((seg_a ^ seg_b) != 0)
344                         goto differ_plus_i;
345         }
346 
347 same:
348         return -1;
349 
350 differ_plus_i:
351         level += i;
352 differ:
353         i = level * 8 + __ffs(seg_a ^ seg_b);
354         return i;
355 }
356 
357 /*
358  * Free an object after stripping the keyring flag off of the pointer.
359  */
360 static void keyring_free_object(void *object)
361 {
362         key_put(keyring_ptr_to_key(object));
363 }
364 
365 /*
366  * Operations for keyring management by the index-tree routines.
367  */
368 static const struct assoc_array_ops keyring_assoc_array_ops = {
369         .get_key_chunk          = keyring_get_key_chunk,
370         .get_object_key_chunk   = keyring_get_object_key_chunk,
371         .compare_object         = keyring_compare_object,
372         .diff_objects           = keyring_diff_objects,
373         .free_object            = keyring_free_object,
374 };
375 
376 /*
377  * Clean up a keyring when it is destroyed.  Unpublish its name if it had one
378  * and dispose of its data.
379  *
380  * The garbage collector detects the final key_put(), removes the keyring from
381  * the serial number tree and then does RCU synchronisation before coming here,
382  * so we shouldn't need to worry about code poking around here with the RCU
383  * readlock held by this time.
384  */
385 static void keyring_destroy(struct key *keyring)
386 {
387         if (keyring->description) {
388                 write_lock(&keyring_name_lock);
389 
390                 if (keyring->type_data.link.next != NULL &&
391                     !list_empty(&keyring->type_data.link))
392                         list_del(&keyring->type_data.link);
393 
394                 write_unlock(&keyring_name_lock);
395         }
396 
397         assoc_array_destroy(&keyring->keys, &keyring_assoc_array_ops);
398 }
399 
400 /*
401  * Describe a keyring for /proc.
402  */
403 static void keyring_describe(const struct key *keyring, struct seq_file *m)
404 {
405         if (keyring->description)
406                 seq_puts(m, keyring->description);
407         else
408                 seq_puts(m, "[anon]");
409 
410         if (key_is_instantiated(keyring)) {
411                 if (keyring->keys.nr_leaves_on_tree != 0)
412                         seq_printf(m, ": %lu", keyring->keys.nr_leaves_on_tree);
413                 else
414                         seq_puts(m, ": empty");
415         }
416 }
417 
418 struct keyring_read_iterator_context {
419         size_t                  qty;
420         size_t                  count;
421         key_serial_t __user     *buffer;
422 };
423 
424 static int keyring_read_iterator(const void *object, void *data)
425 {
426         struct keyring_read_iterator_context *ctx = data;
427         const struct key *key = keyring_ptr_to_key(object);
428         int ret;
429 
430         kenter("{%s,%d},,{%zu/%zu}",
431                key->type->name, key->serial, ctx->count, ctx->qty);
432 
433         if (ctx->count >= ctx->qty)
434                 return 1;
435 
436         ret = put_user(key->serial, ctx->buffer);
437         if (ret < 0)
438                 return ret;
439         ctx->buffer++;
440         ctx->count += sizeof(key->serial);
441         return 0;
442 }
443 
444 /*
445  * Read a list of key IDs from the keyring's contents in binary form
446  *
447  * The keyring's semaphore is read-locked by the caller.  This prevents someone
448  * from modifying it under us - which could cause us to read key IDs multiple
449  * times.
450  */
451 static long keyring_read(const struct key *keyring,
452                          char __user *buffer, size_t buflen)
453 {
454         struct keyring_read_iterator_context ctx;
455         unsigned long nr_keys;
456         int ret;
457 
458         kenter("{%d},,%zu", key_serial(keyring), buflen);
459 
460         if (buflen & (sizeof(key_serial_t) - 1))
461                 return -EINVAL;
462 
463         nr_keys = keyring->keys.nr_leaves_on_tree;
464         if (nr_keys == 0)
465                 return 0;
466 
467         /* Calculate how much data we could return */
468         ctx.qty = nr_keys * sizeof(key_serial_t);
469 
470         if (!buffer || !buflen)
471                 return ctx.qty;
472 
473         if (buflen > ctx.qty)
474                 ctx.qty = buflen;
475 
476         /* Copy the IDs of the subscribed keys into the buffer */
477         ctx.buffer = (key_serial_t __user *)buffer;
478         ctx.count = 0;
479         ret = assoc_array_iterate(&keyring->keys, keyring_read_iterator, &ctx);
480         if (ret < 0) {
481                 kleave(" = %d [iterate]", ret);
482                 return ret;
483         }
484 
485         kleave(" = %zu [ok]", ctx.count);
486         return ctx.count;
487 }
488 
489 /*
490  * Allocate a keyring and link into the destination keyring.
491  */
492 struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
493                           const struct cred *cred, key_perm_t perm,
494                           unsigned long flags, struct key *dest)
495 {
496         struct key *keyring;
497         int ret;
498 
499         keyring = key_alloc(&key_type_keyring, description,
500                             uid, gid, cred, perm, flags);
501         if (!IS_ERR(keyring)) {
502                 ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
503                 if (ret < 0) {
504                         key_put(keyring);
505                         keyring = ERR_PTR(ret);
506                 }
507         }
508 
509         return keyring;
510 }
511 EXPORT_SYMBOL(keyring_alloc);
512 
513 /*
514  * By default, we keys found by getting an exact match on their descriptions.
515  */
516 bool key_default_cmp(const struct key *key,
517                      const struct key_match_data *match_data)
518 {
519         return strcmp(key->description, match_data->raw_data) == 0;
520 }
521 
522 /*
523  * Iteration function to consider each key found.
524  */
525 static int keyring_search_iterator(const void *object, void *iterator_data)
526 {
527         struct keyring_search_context *ctx = iterator_data;
528         const struct key *key = keyring_ptr_to_key(object);
529         unsigned long kflags = key->flags;
530 
531         kenter("{%d}", key->serial);
532 
533         /* ignore keys not of this type */
534         if (key->type != ctx->index_key.type) {
535                 kleave(" = 0 [!type]");
536                 return 0;
537         }
538 
539         /* skip invalidated, revoked and expired keys */
540         if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
541                 if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
542                               (1 << KEY_FLAG_REVOKED))) {
543                         ctx->result = ERR_PTR(-EKEYREVOKED);
544                         kleave(" = %d [invrev]", ctx->skipped_ret);
545                         goto skipped;
546                 }
547 
548                 if (key->expiry && ctx->now.tv_sec >= key->expiry) {
549                         if (!(ctx->flags & KEYRING_SEARCH_SKIP_EXPIRED))
550                                 ctx->result = ERR_PTR(-EKEYEXPIRED);
551                         kleave(" = %d [expire]", ctx->skipped_ret);
552                         goto skipped;
553                 }
554         }
555 
556         /* keys that don't match */
557         if (!ctx->match_data.cmp(key, &ctx->match_data)) {
558                 kleave(" = 0 [!match]");
559                 return 0;
560         }
561 
562         /* key must have search permissions */
563         if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
564             key_task_permission(make_key_ref(key, ctx->possessed),
565                                 ctx->cred, KEY_NEED_SEARCH) < 0) {
566                 ctx->result = ERR_PTR(-EACCES);
567                 kleave(" = %d [!perm]", ctx->skipped_ret);
568                 goto skipped;
569         }
570 
571         if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
572                 /* we set a different error code if we pass a negative key */
573                 if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
574                         smp_rmb();
575                         ctx->result = ERR_PTR(key->type_data.reject_error);
576                         kleave(" = %d [neg]", ctx->skipped_ret);
577                         goto skipped;
578                 }
579         }
580 
581         /* Found */
582         ctx->result = make_key_ref(key, ctx->possessed);
583         kleave(" = 1 [found]");
584         return 1;
585 
586 skipped:
587         return ctx->skipped_ret;
588 }
589 
590 /*
591  * Search inside a keyring for a key.  We can search by walking to it
592  * directly based on its index-key or we can iterate over the entire
593  * tree looking for it, based on the match function.
594  */
595 static int search_keyring(struct key *keyring, struct keyring_search_context *ctx)
596 {
597         if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_DIRECT) {
598                 const void *object;
599 
600                 object = assoc_array_find(&keyring->keys,
601                                           &keyring_assoc_array_ops,
602                                           &ctx->index_key);
603                 return object ? ctx->iterator(object, ctx) : 0;
604         }
605         return assoc_array_iterate(&keyring->keys, ctx->iterator, ctx);
606 }
607 
608 /*
609  * Search a tree of keyrings that point to other keyrings up to the maximum
610  * depth.
611  */
612 static bool search_nested_keyrings(struct key *keyring,
613                                    struct keyring_search_context *ctx)
614 {
615         struct {
616                 struct key *keyring;
617                 struct assoc_array_node *node;
618                 int slot;
619         } stack[KEYRING_SEARCH_MAX_DEPTH];
620 
621         struct assoc_array_shortcut *shortcut;
622         struct assoc_array_node *node;
623         struct assoc_array_ptr *ptr;
624         struct key *key;
625         int sp = 0, slot;
626 
627         kenter("{%d},{%s,%s}",
628                keyring->serial,
629                ctx->index_key.type->name,
630                ctx->index_key.description);
631 
632 #define STATE_CHECKS (KEYRING_SEARCH_NO_STATE_CHECK | KEYRING_SEARCH_DO_STATE_CHECK)
633         BUG_ON((ctx->flags & STATE_CHECKS) == 0 ||
634                (ctx->flags & STATE_CHECKS) == STATE_CHECKS);
635 
636         if (ctx->index_key.description)
637                 ctx->index_key.desc_len = strlen(ctx->index_key.description);
638 
639         /* Check to see if this top-level keyring is what we are looking for
640          * and whether it is valid or not.
641          */
642         if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_ITERATE ||
643             keyring_compare_object(keyring, &ctx->index_key)) {
644                 ctx->skipped_ret = 2;
645                 switch (ctx->iterator(keyring_key_to_ptr(keyring), ctx)) {
646                 case 1:
647                         goto found;
648                 case 2:
649                         return false;
650                 default:
651                         break;
652                 }
653         }
654 
655         ctx->skipped_ret = 0;
656 
657         /* Start processing a new keyring */
658 descend_to_keyring:
659         kdebug("descend to %d", keyring->serial);
660         if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
661                               (1 << KEY_FLAG_REVOKED)))
662                 goto not_this_keyring;
663 
664         /* Search through the keys in this keyring before its searching its
665          * subtrees.
666          */
667         if (search_keyring(keyring, ctx))
668                 goto found;
669 
670         /* Then manually iterate through the keyrings nested in this one.
671          *
672          * Start from the root node of the index tree.  Because of the way the
673          * hash function has been set up, keyrings cluster on the leftmost
674          * branch of the root node (root slot 0) or in the root node itself.
675          * Non-keyrings avoid the leftmost branch of the root entirely (root
676          * slots 1-15).
677          */
678         ptr = ACCESS_ONCE(keyring->keys.root);
679         if (!ptr)
680                 goto not_this_keyring;
681 
682         if (assoc_array_ptr_is_shortcut(ptr)) {
683                 /* If the root is a shortcut, either the keyring only contains
684                  * keyring pointers (everything clusters behind root slot 0) or
685                  * doesn't contain any keyring pointers.
686                  */
687                 shortcut = assoc_array_ptr_to_shortcut(ptr);
688                 smp_read_barrier_depends();
689                 if ((shortcut->index_key[0] & ASSOC_ARRAY_FAN_MASK) != 0)
690                         goto not_this_keyring;
691 
692                 ptr = ACCESS_ONCE(shortcut->next_node);
693                 node = assoc_array_ptr_to_node(ptr);
694                 goto begin_node;
695         }
696 
697         node = assoc_array_ptr_to_node(ptr);
698         smp_read_barrier_depends();
699 
700         ptr = node->slots[0];
701         if (!assoc_array_ptr_is_meta(ptr))
702                 goto begin_node;
703 
704 descend_to_node:
705         /* Descend to a more distal node in this keyring's content tree and go
706          * through that.
707          */
708         kdebug("descend");
709         if (assoc_array_ptr_is_shortcut(ptr)) {
710                 shortcut = assoc_array_ptr_to_shortcut(ptr);
711                 smp_read_barrier_depends();
712                 ptr = ACCESS_ONCE(shortcut->next_node);
713                 BUG_ON(!assoc_array_ptr_is_node(ptr));
714         }
715         node = assoc_array_ptr_to_node(ptr);
716 
717 begin_node:
718         kdebug("begin_node");
719         smp_read_barrier_depends();
720         slot = 0;
721 ascend_to_node:
722         /* Go through the slots in a node */
723         for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
724                 ptr = ACCESS_ONCE(node->slots[slot]);
725 
726                 if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
727                         goto descend_to_node;
728 
729                 if (!keyring_ptr_is_keyring(ptr))
730                         continue;
731 
732                 key = keyring_ptr_to_key(ptr);
733 
734                 if (sp >= KEYRING_SEARCH_MAX_DEPTH) {
735                         if (ctx->flags & KEYRING_SEARCH_DETECT_TOO_DEEP) {
736                                 ctx->result = ERR_PTR(-ELOOP);
737                                 return false;
738                         }
739                         goto not_this_keyring;
740                 }
741 
742                 /* Search a nested keyring */
743                 if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
744                     key_task_permission(make_key_ref(key, ctx->possessed),
745                                         ctx->cred, KEY_NEED_SEARCH) < 0)
746                         continue;
747 
748                 /* stack the current position */
749                 stack[sp].keyring = keyring;
750                 stack[sp].node = node;
751                 stack[sp].slot = slot;
752                 sp++;
753 
754                 /* begin again with the new keyring */
755                 keyring = key;
756                 goto descend_to_keyring;
757         }
758 
759         /* We've dealt with all the slots in the current node, so now we need
760          * to ascend to the parent and continue processing there.
761          */
762         ptr = ACCESS_ONCE(node->back_pointer);
763         slot = node->parent_slot;
764 
765         if (ptr && assoc_array_ptr_is_shortcut(ptr)) {
766                 shortcut = assoc_array_ptr_to_shortcut(ptr);
767                 smp_read_barrier_depends();
768                 ptr = ACCESS_ONCE(shortcut->back_pointer);
769                 slot = shortcut->parent_slot;
770         }
771         if (!ptr)
772                 goto not_this_keyring;
773         node = assoc_array_ptr_to_node(ptr);
774         smp_read_barrier_depends();
775         slot++;
776 
777         /* If we've ascended to the root (zero backpointer), we must have just
778          * finished processing the leftmost branch rather than the root slots -
779          * so there can't be any more keyrings for us to find.
780          */
781         if (node->back_pointer) {
782                 kdebug("ascend %d", slot);
783                 goto ascend_to_node;
784         }
785 
786         /* The keyring we're looking at was disqualified or didn't contain a
787          * matching key.
788          */
789 not_this_keyring:
790         kdebug("not_this_keyring %d", sp);
791         if (sp <= 0) {
792                 kleave(" = false");
793                 return false;
794         }
795 
796         /* Resume the processing of a keyring higher up in the tree */
797         sp--;
798         keyring = stack[sp].keyring;
799         node = stack[sp].node;
800         slot = stack[sp].slot + 1;
801         kdebug("ascend to %d [%d]", keyring->serial, slot);
802         goto ascend_to_node;
803 
804         /* We found a viable match */
805 found:
806         key = key_ref_to_ptr(ctx->result);
807         key_check(key);
808         if (!(ctx->flags & KEYRING_SEARCH_NO_UPDATE_TIME)) {
809                 key->last_used_at = ctx->now.tv_sec;
810                 keyring->last_used_at = ctx->now.tv_sec;
811                 while (sp > 0)
812                         stack[--sp].keyring->last_used_at = ctx->now.tv_sec;
813         }
814         kleave(" = true");
815         return true;
816 }
817 
818 /**
819  * keyring_search_aux - Search a keyring tree for a key matching some criteria
820  * @keyring_ref: A pointer to the keyring with possession indicator.
821  * @ctx: The keyring search context.
822  *
823  * Search the supplied keyring tree for a key that matches the criteria given.
824  * The root keyring and any linked keyrings must grant Search permission to the
825  * caller to be searchable and keys can only be found if they too grant Search
826  * to the caller. The possession flag on the root keyring pointer controls use
827  * of the possessor bits in permissions checking of the entire tree.  In
828  * addition, the LSM gets to forbid keyring searches and key matches.
829  *
830  * The search is performed as a breadth-then-depth search up to the prescribed
831  * limit (KEYRING_SEARCH_MAX_DEPTH).
832  *
833  * Keys are matched to the type provided and are then filtered by the match
834  * function, which is given the description to use in any way it sees fit.  The
835  * match function may use any attributes of a key that it wishes to to
836  * determine the match.  Normally the match function from the key type would be
837  * used.
838  *
839  * RCU can be used to prevent the keyring key lists from disappearing without
840  * the need to take lots of locks.
841  *
842  * Returns a pointer to the found key and increments the key usage count if
843  * successful; -EAGAIN if no matching keys were found, or if expired or revoked
844  * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
845  * specified keyring wasn't a keyring.
846  *
847  * In the case of a successful return, the possession attribute from
848  * @keyring_ref is propagated to the returned key reference.
849  */
850 key_ref_t keyring_search_aux(key_ref_t keyring_ref,
851                              struct keyring_search_context *ctx)
852 {
853         struct key *keyring;
854         long err;
855 
856         ctx->iterator = keyring_search_iterator;
857         ctx->possessed = is_key_possessed(keyring_ref);
858         ctx->result = ERR_PTR(-EAGAIN);
859 
860         keyring = key_ref_to_ptr(keyring_ref);
861         key_check(keyring);
862 
863         if (keyring->type != &key_type_keyring)
864                 return ERR_PTR(-ENOTDIR);
865 
866         if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM)) {
867                 err = key_task_permission(keyring_ref, ctx->cred, KEY_NEED_SEARCH);
868                 if (err < 0)
869                         return ERR_PTR(err);
870         }
871 
872         rcu_read_lock();
873         ctx->now = current_kernel_time();
874         if (search_nested_keyrings(keyring, ctx))
875                 __key_get(key_ref_to_ptr(ctx->result));
876         rcu_read_unlock();
877         return ctx->result;
878 }
879 
880 /**
881  * keyring_search - Search the supplied keyring tree for a matching key
882  * @keyring: The root of the keyring tree to be searched.
883  * @type: The type of keyring we want to find.
884  * @description: The name of the keyring we want to find.
885  *
886  * As keyring_search_aux() above, but using the current task's credentials and
887  * type's default matching function and preferred search method.
888  */
889 key_ref_t keyring_search(key_ref_t keyring,
890                          struct key_type *type,
891                          const char *description)
892 {
893         struct keyring_search_context ctx = {
894                 .index_key.type         = type,
895                 .index_key.description  = description,
896                 .cred                   = current_cred(),
897                 .match_data.cmp         = key_default_cmp,
898                 .match_data.raw_data    = description,
899                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
900                 .flags                  = KEYRING_SEARCH_DO_STATE_CHECK,
901         };
902         key_ref_t key;
903         int ret;
904 
905         if (type->match_preparse) {
906                 ret = type->match_preparse(&ctx.match_data);
907                 if (ret < 0)
908                         return ERR_PTR(ret);
909         }
910 
911         key = keyring_search_aux(keyring, &ctx);
912 
913         if (type->match_free)
914                 type->match_free(&ctx.match_data);
915         return key;
916 }
917 EXPORT_SYMBOL(keyring_search);
918 
919 /*
920  * Search the given keyring for a key that might be updated.
921  *
922  * The caller must guarantee that the keyring is a keyring and that the
923  * permission is granted to modify the keyring as no check is made here.  The
924  * caller must also hold a lock on the keyring semaphore.
925  *
926  * Returns a pointer to the found key with usage count incremented if
927  * successful and returns NULL if not found.  Revoked and invalidated keys are
928  * skipped over.
929  *
930  * If successful, the possession indicator is propagated from the keyring ref
931  * to the returned key reference.
932  */
933 key_ref_t find_key_to_update(key_ref_t keyring_ref,
934                              const struct keyring_index_key *index_key)
935 {
936         struct key *keyring, *key;
937         const void *object;
938 
939         keyring = key_ref_to_ptr(keyring_ref);
940 
941         kenter("{%d},{%s,%s}",
942                keyring->serial, index_key->type->name, index_key->description);
943 
944         object = assoc_array_find(&keyring->keys, &keyring_assoc_array_ops,
945                                   index_key);
946 
947         if (object)
948                 goto found;
949 
950         kleave(" = NULL");
951         return NULL;
952 
953 found:
954         key = keyring_ptr_to_key(object);
955         if (key->flags & ((1 << KEY_FLAG_INVALIDATED) |
956                           (1 << KEY_FLAG_REVOKED))) {
957                 kleave(" = NULL [x]");
958                 return NULL;
959         }
960         __key_get(key);
961         kleave(" = {%d}", key->serial);
962         return make_key_ref(key, is_key_possessed(keyring_ref));
963 }
964 
965 /*
966  * Find a keyring with the specified name.
967  *
968  * All named keyrings in the current user namespace are searched, provided they
969  * grant Search permission directly to the caller (unless this check is
970  * skipped).  Keyrings whose usage points have reached zero or who have been
971  * revoked are skipped.
972  *
973  * Returns a pointer to the keyring with the keyring's refcount having being
974  * incremented on success.  -ENOKEY is returned if a key could not be found.
975  */
976 struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
977 {
978         struct key *keyring;
979         int bucket;
980 
981         if (!name)
982                 return ERR_PTR(-EINVAL);
983 
984         bucket = keyring_hash(name);
985 
986         read_lock(&keyring_name_lock);
987 
988         if (keyring_name_hash[bucket].next) {
989                 /* search this hash bucket for a keyring with a matching name
990                  * that's readable and that hasn't been revoked */
991                 list_for_each_entry(keyring,
992                                     &keyring_name_hash[bucket],
993                                     type_data.link
994                                     ) {
995                         if (!kuid_has_mapping(current_user_ns(), keyring->user->uid))
996                                 continue;
997 
998                         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
999                                 continue;
1000 
1001                         if (strcmp(keyring->description, name) != 0)
1002                                 continue;
1003 
1004                         if (!skip_perm_check &&
1005                             key_permission(make_key_ref(keyring, 0),
1006                                            KEY_NEED_SEARCH) < 0)
1007                                 continue;
1008 
1009                         /* we've got a match but we might end up racing with
1010                          * key_cleanup() if the keyring is currently 'dead'
1011                          * (ie. it has a zero usage count) */
1012                         if (!atomic_inc_not_zero(&keyring->usage))
1013                                 continue;
1014                         keyring->last_used_at = current_kernel_time().tv_sec;
1015                         goto out;
1016                 }
1017         }
1018 
1019         keyring = ERR_PTR(-ENOKEY);
1020 out:
1021         read_unlock(&keyring_name_lock);
1022         return keyring;
1023 }
1024 
1025 static int keyring_detect_cycle_iterator(const void *object,
1026                                          void *iterator_data)
1027 {
1028         struct keyring_search_context *ctx = iterator_data;
1029         const struct key *key = keyring_ptr_to_key(object);
1030 
1031         kenter("{%d}", key->serial);
1032 
1033         /* We might get a keyring with matching index-key that is nonetheless a
1034          * different keyring. */
1035         if (key != ctx->match_data.raw_data)
1036                 return 0;
1037 
1038         ctx->result = ERR_PTR(-EDEADLK);
1039         return 1;
1040 }
1041 
1042 /*
1043  * See if a cycle will will be created by inserting acyclic tree B in acyclic
1044  * tree A at the topmost level (ie: as a direct child of A).
1045  *
1046  * Since we are adding B to A at the top level, checking for cycles should just
1047  * be a matter of seeing if node A is somewhere in tree B.
1048  */
1049 static int keyring_detect_cycle(struct key *A, struct key *B)
1050 {
1051         struct keyring_search_context ctx = {
1052                 .index_key              = A->index_key,
1053                 .match_data.raw_data    = A,
1054                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
1055                 .iterator               = keyring_detect_cycle_iterator,
1056                 .flags                  = (KEYRING_SEARCH_NO_STATE_CHECK |
1057                                            KEYRING_SEARCH_NO_UPDATE_TIME |
1058                                            KEYRING_SEARCH_NO_CHECK_PERM |
1059                                            KEYRING_SEARCH_DETECT_TOO_DEEP),
1060         };
1061 
1062         rcu_read_lock();
1063         search_nested_keyrings(B, &ctx);
1064         rcu_read_unlock();
1065         return PTR_ERR(ctx.result) == -EAGAIN ? 0 : PTR_ERR(ctx.result);
1066 }
1067 
1068 /*
1069  * Preallocate memory so that a key can be linked into to a keyring.
1070  */
1071 int __key_link_begin(struct key *keyring,
1072                      const struct keyring_index_key *index_key,
1073                      struct assoc_array_edit **_edit)
1074         __acquires(&keyring->sem)
1075         __acquires(&keyring_serialise_link_sem)
1076 {
1077         struct assoc_array_edit *edit;
1078         int ret;
1079 
1080         kenter("%d,%s,%s,",
1081                keyring->serial, index_key->type->name, index_key->description);
1082 
1083         BUG_ON(index_key->desc_len == 0);
1084 
1085         if (keyring->type != &key_type_keyring)
1086                 return -ENOTDIR;
1087 
1088         down_write(&keyring->sem);
1089 
1090         ret = -EKEYREVOKED;
1091         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
1092                 goto error_krsem;
1093 
1094         /* serialise link/link calls to prevent parallel calls causing a cycle
1095          * when linking two keyring in opposite orders */
1096         if (index_key->type == &key_type_keyring)
1097                 down_write(&keyring_serialise_link_sem);
1098 
1099         /* Create an edit script that will insert/replace the key in the
1100          * keyring tree.
1101          */
1102         edit = assoc_array_insert(&keyring->keys,
1103                                   &keyring_assoc_array_ops,
1104                                   index_key,
1105                                   NULL);
1106         if (IS_ERR(edit)) {
1107                 ret = PTR_ERR(edit);
1108                 goto error_sem;
1109         }
1110 
1111         /* If we're not replacing a link in-place then we're going to need some
1112          * extra quota.
1113          */
1114         if (!edit->dead_leaf) {
1115                 ret = key_payload_reserve(keyring,
1116                                           keyring->datalen + KEYQUOTA_LINK_BYTES);
1117                 if (ret < 0)
1118                         goto error_cancel;
1119         }
1120 
1121         *_edit = edit;
1122         kleave(" = 0");
1123         return 0;
1124 
1125 error_cancel:
1126         assoc_array_cancel_edit(edit);
1127 error_sem:
1128         if (index_key->type == &key_type_keyring)
1129                 up_write(&keyring_serialise_link_sem);
1130 error_krsem:
1131         up_write(&keyring->sem);
1132         kleave(" = %d", ret);
1133         return ret;
1134 }
1135 
1136 /*
1137  * Check already instantiated keys aren't going to be a problem.
1138  *
1139  * The caller must have called __key_link_begin(). Don't need to call this for
1140  * keys that were created since __key_link_begin() was called.
1141  */
1142 int __key_link_check_live_key(struct key *keyring, struct key *key)
1143 {
1144         if (key->type == &key_type_keyring)
1145                 /* check that we aren't going to create a cycle by linking one
1146                  * keyring to another */
1147                 return keyring_detect_cycle(keyring, key);
1148         return 0;
1149 }
1150 
1151 /*
1152  * Link a key into to a keyring.
1153  *
1154  * Must be called with __key_link_begin() having being called.  Discards any
1155  * already extant link to matching key if there is one, so that each keyring
1156  * holds at most one link to any given key of a particular type+description
1157  * combination.
1158  */
1159 void __key_link(struct key *key, struct assoc_array_edit **_edit)
1160 {
1161         __key_get(key);
1162         assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key));
1163         assoc_array_apply_edit(*_edit);
1164         *_edit = NULL;
1165 }
1166 
1167 /*
1168  * Finish linking a key into to a keyring.
1169  *
1170  * Must be called with __key_link_begin() having being called.
1171  */
1172 void __key_link_end(struct key *keyring,
1173                     const struct keyring_index_key *index_key,
1174                     struct assoc_array_edit *edit)
1175         __releases(&keyring->sem)
1176         __releases(&keyring_serialise_link_sem)
1177 {
1178         BUG_ON(index_key->type == NULL);
1179         kenter("%d,%s,", keyring->serial, index_key->type->name);
1180 
1181         if (index_key->type == &key_type_keyring)
1182                 up_write(&keyring_serialise_link_sem);
1183 
1184         if (edit) {
1185                 if (!edit->dead_leaf) {
1186                         key_payload_reserve(keyring,
1187                                 keyring->datalen - KEYQUOTA_LINK_BYTES);
1188                 }
1189                 assoc_array_cancel_edit(edit);
1190         }
1191         up_write(&keyring->sem);
1192 }
1193 
1194 /**
1195  * key_link - Link a key to a keyring
1196  * @keyring: The keyring to make the link in.
1197  * @key: The key to link to.
1198  *
1199  * Make a link in a keyring to a key, such that the keyring holds a reference
1200  * on that key and the key can potentially be found by searching that keyring.
1201  *
1202  * This function will write-lock the keyring's semaphore and will consume some
1203  * of the user's key data quota to hold the link.
1204  *
1205  * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
1206  * -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
1207  * full, -EDQUOT if there is insufficient key data quota remaining to add
1208  * another link or -ENOMEM if there's insufficient memory.
1209  *
1210  * It is assumed that the caller has checked that it is permitted for a link to
1211  * be made (the keyring should have Write permission and the key Link
1212  * permission).
1213  */
1214 int key_link(struct key *keyring, struct key *key)
1215 {
1216         struct assoc_array_edit *edit;
1217         int ret;
1218 
1219         kenter("{%d,%d}", keyring->serial, atomic_read(&keyring->usage));
1220 
1221         key_check(keyring);
1222         key_check(key);
1223 
1224         if (test_bit(KEY_FLAG_TRUSTED_ONLY, &keyring->flags) &&
1225             !test_bit(KEY_FLAG_TRUSTED, &key->flags))
1226                 return -EPERM;
1227 
1228         ret = __key_link_begin(keyring, &key->index_key, &edit);
1229         if (ret == 0) {
1230                 kdebug("begun {%d,%d}", keyring->serial, atomic_read(&keyring->usage));
1231                 ret = __key_link_check_live_key(keyring, key);
1232                 if (ret == 0)
1233                         __key_link(key, &edit);
1234                 __key_link_end(keyring, &key->index_key, edit);
1235         }
1236 
1237         kleave(" = %d {%d,%d}", ret, keyring->serial, atomic_read(&keyring->usage));
1238         return ret;
1239 }
1240 EXPORT_SYMBOL(key_link);
1241 
1242 /**
1243  * key_unlink - Unlink the first link to a key from a keyring.
1244  * @keyring: The keyring to remove the link from.
1245  * @key: The key the link is to.
1246  *
1247  * Remove a link from a keyring to a key.
1248  *
1249  * This function will write-lock the keyring's semaphore.
1250  *
1251  * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
1252  * the key isn't linked to by the keyring or -ENOMEM if there's insufficient
1253  * memory.
1254  *
1255  * It is assumed that the caller has checked that it is permitted for a link to
1256  * be removed (the keyring should have Write permission; no permissions are
1257  * required on the key).
1258  */
1259 int key_unlink(struct key *keyring, struct key *key)
1260 {
1261         struct assoc_array_edit *edit;
1262         int ret;
1263 
1264         key_check(keyring);
1265         key_check(key);
1266 
1267         if (keyring->type != &key_type_keyring)
1268                 return -ENOTDIR;
1269 
1270         down_write(&keyring->sem);
1271 
1272         edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops,
1273                                   &key->index_key);
1274         if (IS_ERR(edit)) {
1275                 ret = PTR_ERR(edit);
1276                 goto error;
1277         }
1278         ret = -ENOENT;
1279         if (edit == NULL)
1280                 goto error;
1281 
1282         assoc_array_apply_edit(edit);
1283         key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES);
1284         ret = 0;
1285 
1286 error:
1287         up_write(&keyring->sem);
1288         return ret;
1289 }
1290 EXPORT_SYMBOL(key_unlink);
1291 
1292 /**
1293  * keyring_clear - Clear a keyring
1294  * @keyring: The keyring to clear.
1295  *
1296  * Clear the contents of the specified keyring.
1297  *
1298  * Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
1299  */
1300 int keyring_clear(struct key *keyring)
1301 {
1302         struct assoc_array_edit *edit;
1303         int ret;
1304 
1305         if (keyring->type != &key_type_keyring)
1306                 return -ENOTDIR;
1307 
1308         down_write(&keyring->sem);
1309 
1310         edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
1311         if (IS_ERR(edit)) {
1312                 ret = PTR_ERR(edit);
1313         } else {
1314                 if (edit)
1315                         assoc_array_apply_edit(edit);
1316                 key_payload_reserve(keyring, 0);
1317                 ret = 0;
1318         }
1319 
1320         up_write(&keyring->sem);
1321         return ret;
1322 }
1323 EXPORT_SYMBOL(keyring_clear);
1324 
1325 /*
1326  * Dispose of the links from a revoked keyring.
1327  *
1328  * This is called with the key sem write-locked.
1329  */
1330 static void keyring_revoke(struct key *keyring)
1331 {
1332         struct assoc_array_edit *edit;
1333 
1334         edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
1335         if (!IS_ERR(edit)) {
1336                 if (edit)
1337                         assoc_array_apply_edit(edit);
1338                 key_payload_reserve(keyring, 0);
1339         }
1340 }
1341 
1342 static bool keyring_gc_select_iterator(void *object, void *iterator_data)
1343 {
1344         struct key *key = keyring_ptr_to_key(object);
1345         time_t *limit = iterator_data;
1346 
1347         if (key_is_dead(key, *limit))
1348                 return false;
1349         key_get(key);
1350         return true;
1351 }
1352 
1353 static int keyring_gc_check_iterator(const void *object, void *iterator_data)
1354 {
1355         const struct key *key = keyring_ptr_to_key(object);
1356         time_t *limit = iterator_data;
1357 
1358         key_check(key);
1359         return key_is_dead(key, *limit);
1360 }
1361 
1362 /*
1363  * Garbage collect pointers from a keyring.
1364  *
1365  * Not called with any locks held.  The keyring's key struct will not be
1366  * deallocated under us as only our caller may deallocate it.
1367  */
1368 void keyring_gc(struct key *keyring, time_t limit)
1369 {
1370         int result;
1371 
1372         kenter("%x{%s}", keyring->serial, keyring->description ?: "");
1373 
1374         if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
1375                               (1 << KEY_FLAG_REVOKED)))
1376                 goto dont_gc;
1377 
1378         /* scan the keyring looking for dead keys */
1379         rcu_read_lock();
1380         result = assoc_array_iterate(&keyring->keys,
1381                                      keyring_gc_check_iterator, &limit);
1382         rcu_read_unlock();
1383         if (result == true)
1384                 goto do_gc;
1385 
1386 dont_gc:
1387         kleave(" [no gc]");
1388         return;
1389 
1390 do_gc:
1391         down_write(&keyring->sem);
1392         assoc_array_gc(&keyring->keys, &keyring_assoc_array_ops,
1393                        keyring_gc_select_iterator, &limit);
1394         up_write(&keyring->sem);
1395         kleave(" [gc]");
1396 }
1397 

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