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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/export.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->name_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->name_link.next != NULL &&
391                     !list_empty(&keyring->name_link))
392                         list_del(&keyring->name_link);
393 
394                 write_unlock(&keyring_name_lock);
395         }
396 
397         if (keyring->restrict_link) {
398                 struct key_restriction *keyres = keyring->restrict_link;
399 
400                 key_put(keyres->key);
401                 kfree(keyres);
402         }
403 
404         assoc_array_destroy(&keyring->keys, &keyring_assoc_array_ops);
405 }
406 
407 /*
408  * Describe a keyring for /proc.
409  */
410 static void keyring_describe(const struct key *keyring, struct seq_file *m)
411 {
412         if (keyring->description)
413                 seq_puts(m, keyring->description);
414         else
415                 seq_puts(m, "[anon]");
416 
417         if (key_is_positive(keyring)) {
418                 if (keyring->keys.nr_leaves_on_tree != 0)
419                         seq_printf(m, ": %lu", keyring->keys.nr_leaves_on_tree);
420                 else
421                         seq_puts(m, ": empty");
422         }
423 }
424 
425 struct keyring_read_iterator_context {
426         size_t                  buflen;
427         size_t                  count;
428         key_serial_t __user     *buffer;
429 };
430 
431 static int keyring_read_iterator(const void *object, void *data)
432 {
433         struct keyring_read_iterator_context *ctx = data;
434         const struct key *key = keyring_ptr_to_key(object);
435         int ret;
436 
437         kenter("{%s,%d},,{%zu/%zu}",
438                key->type->name, key->serial, ctx->count, ctx->buflen);
439 
440         if (ctx->count >= ctx->buflen)
441                 return 1;
442 
443         ret = put_user(key->serial, ctx->buffer);
444         if (ret < 0)
445                 return ret;
446         ctx->buffer++;
447         ctx->count += sizeof(key->serial);
448         return 0;
449 }
450 
451 /*
452  * Read a list of key IDs from the keyring's contents in binary form
453  *
454  * The keyring's semaphore is read-locked by the caller.  This prevents someone
455  * from modifying it under us - which could cause us to read key IDs multiple
456  * times.
457  */
458 static long keyring_read(const struct key *keyring,
459                          char __user *buffer, size_t buflen)
460 {
461         struct keyring_read_iterator_context ctx;
462         long ret;
463 
464         kenter("{%d},,%zu", key_serial(keyring), buflen);
465 
466         if (buflen & (sizeof(key_serial_t) - 1))
467                 return -EINVAL;
468 
469         /* Copy as many key IDs as fit into the buffer */
470         if (buffer && buflen) {
471                 ctx.buffer = (key_serial_t __user *)buffer;
472                 ctx.buflen = buflen;
473                 ctx.count = 0;
474                 ret = assoc_array_iterate(&keyring->keys,
475                                           keyring_read_iterator, &ctx);
476                 if (ret < 0) {
477                         kleave(" = %ld [iterate]", ret);
478                         return ret;
479                 }
480         }
481 
482         /* Return the size of the buffer needed */
483         ret = keyring->keys.nr_leaves_on_tree * sizeof(key_serial_t);
484         if (ret <= buflen)
485                 kleave("= %ld [ok]", ret);
486         else
487                 kleave("= %ld [buffer too small]", ret);
488         return ret;
489 }
490 
491 /*
492  * Allocate a keyring and link into the destination keyring.
493  */
494 struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
495                           const struct cred *cred, key_perm_t perm,
496                           unsigned long flags,
497                           struct key_restriction *restrict_link,
498                           struct key *dest)
499 {
500         struct key *keyring;
501         int ret;
502 
503         keyring = key_alloc(&key_type_keyring, description,
504                             uid, gid, cred, perm, flags, restrict_link);
505         if (!IS_ERR(keyring)) {
506                 ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
507                 if (ret < 0) {
508                         key_put(keyring);
509                         keyring = ERR_PTR(ret);
510                 }
511         }
512 
513         return keyring;
514 }
515 EXPORT_SYMBOL(keyring_alloc);
516 
517 /**
518  * restrict_link_reject - Give -EPERM to restrict link
519  * @keyring: The keyring being added to.
520  * @type: The type of key being added.
521  * @payload: The payload of the key intended to be added.
522  * @data: Additional data for evaluating restriction.
523  *
524  * Reject the addition of any links to a keyring.  It can be overridden by
525  * passing KEY_ALLOC_BYPASS_RESTRICTION to key_instantiate_and_link() when
526  * adding a key to a keyring.
527  *
528  * This is meant to be stored in a key_restriction structure which is passed
529  * in the restrict_link parameter to keyring_alloc().
530  */
531 int restrict_link_reject(struct key *keyring,
532                          const struct key_type *type,
533                          const union key_payload *payload,
534                          struct key *restriction_key)
535 {
536         return -EPERM;
537 }
538 
539 /*
540  * By default, we keys found by getting an exact match on their descriptions.
541  */
542 bool key_default_cmp(const struct key *key,
543                      const struct key_match_data *match_data)
544 {
545         return strcmp(key->description, match_data->raw_data) == 0;
546 }
547 
548 /*
549  * Iteration function to consider each key found.
550  */
551 static int keyring_search_iterator(const void *object, void *iterator_data)
552 {
553         struct keyring_search_context *ctx = iterator_data;
554         const struct key *key = keyring_ptr_to_key(object);
555         unsigned long kflags = READ_ONCE(key->flags);
556         short state = READ_ONCE(key->state);
557 
558         kenter("{%d}", key->serial);
559 
560         /* ignore keys not of this type */
561         if (key->type != ctx->index_key.type) {
562                 kleave(" = 0 [!type]");
563                 return 0;
564         }
565 
566         /* skip invalidated, revoked and expired keys */
567         if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
568                 time64_t expiry = READ_ONCE(key->expiry);
569 
570                 if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
571                               (1 << KEY_FLAG_REVOKED))) {
572                         ctx->result = ERR_PTR(-EKEYREVOKED);
573                         kleave(" = %d [invrev]", ctx->skipped_ret);
574                         goto skipped;
575                 }
576 
577                 if (expiry && ctx->now >= expiry) {
578                         if (!(ctx->flags & KEYRING_SEARCH_SKIP_EXPIRED))
579                                 ctx->result = ERR_PTR(-EKEYEXPIRED);
580                         kleave(" = %d [expire]", ctx->skipped_ret);
581                         goto skipped;
582                 }
583         }
584 
585         /* keys that don't match */
586         if (!ctx->match_data.cmp(key, &ctx->match_data)) {
587                 kleave(" = 0 [!match]");
588                 return 0;
589         }
590 
591         /* key must have search permissions */
592         if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
593             key_task_permission(make_key_ref(key, ctx->possessed),
594                                 ctx->cred, KEY_NEED_SEARCH) < 0) {
595                 ctx->result = ERR_PTR(-EACCES);
596                 kleave(" = %d [!perm]", ctx->skipped_ret);
597                 goto skipped;
598         }
599 
600         if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
601                 /* we set a different error code if we pass a negative key */
602                 if (state < 0) {
603                         ctx->result = ERR_PTR(state);
604                         kleave(" = %d [neg]", ctx->skipped_ret);
605                         goto skipped;
606                 }
607         }
608 
609         /* Found */
610         ctx->result = make_key_ref(key, ctx->possessed);
611         kleave(" = 1 [found]");
612         return 1;
613 
614 skipped:
615         return ctx->skipped_ret;
616 }
617 
618 /*
619  * Search inside a keyring for a key.  We can search by walking to it
620  * directly based on its index-key or we can iterate over the entire
621  * tree looking for it, based on the match function.
622  */
623 static int search_keyring(struct key *keyring, struct keyring_search_context *ctx)
624 {
625         if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_DIRECT) {
626                 const void *object;
627 
628                 object = assoc_array_find(&keyring->keys,
629                                           &keyring_assoc_array_ops,
630                                           &ctx->index_key);
631                 return object ? ctx->iterator(object, ctx) : 0;
632         }
633         return assoc_array_iterate(&keyring->keys, ctx->iterator, ctx);
634 }
635 
636 /*
637  * Search a tree of keyrings that point to other keyrings up to the maximum
638  * depth.
639  */
640 static bool search_nested_keyrings(struct key *keyring,
641                                    struct keyring_search_context *ctx)
642 {
643         struct {
644                 struct key *keyring;
645                 struct assoc_array_node *node;
646                 int slot;
647         } stack[KEYRING_SEARCH_MAX_DEPTH];
648 
649         struct assoc_array_shortcut *shortcut;
650         struct assoc_array_node *node;
651         struct assoc_array_ptr *ptr;
652         struct key *key;
653         int sp = 0, slot;
654 
655         kenter("{%d},{%s,%s}",
656                keyring->serial,
657                ctx->index_key.type->name,
658                ctx->index_key.description);
659 
660 #define STATE_CHECKS (KEYRING_SEARCH_NO_STATE_CHECK | KEYRING_SEARCH_DO_STATE_CHECK)
661         BUG_ON((ctx->flags & STATE_CHECKS) == 0 ||
662                (ctx->flags & STATE_CHECKS) == STATE_CHECKS);
663 
664         /* Check to see if this top-level keyring is what we are looking for
665          * and whether it is valid or not.
666          */
667         if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_ITERATE ||
668             keyring_compare_object(keyring, &ctx->index_key)) {
669                 ctx->skipped_ret = 2;
670                 switch (ctx->iterator(keyring_key_to_ptr(keyring), ctx)) {
671                 case 1:
672                         goto found;
673                 case 2:
674                         return false;
675                 default:
676                         break;
677                 }
678         }
679 
680         ctx->skipped_ret = 0;
681 
682         /* Start processing a new keyring */
683 descend_to_keyring:
684         kdebug("descend to %d", keyring->serial);
685         if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
686                               (1 << KEY_FLAG_REVOKED)))
687                 goto not_this_keyring;
688 
689         /* Search through the keys in this keyring before its searching its
690          * subtrees.
691          */
692         if (search_keyring(keyring, ctx))
693                 goto found;
694 
695         /* Then manually iterate through the keyrings nested in this one.
696          *
697          * Start from the root node of the index tree.  Because of the way the
698          * hash function has been set up, keyrings cluster on the leftmost
699          * branch of the root node (root slot 0) or in the root node itself.
700          * Non-keyrings avoid the leftmost branch of the root entirely (root
701          * slots 1-15).
702          */
703         ptr = READ_ONCE(keyring->keys.root);
704         if (!ptr)
705                 goto not_this_keyring;
706 
707         if (assoc_array_ptr_is_shortcut(ptr)) {
708                 /* If the root is a shortcut, either the keyring only contains
709                  * keyring pointers (everything clusters behind root slot 0) or
710                  * doesn't contain any keyring pointers.
711                  */
712                 shortcut = assoc_array_ptr_to_shortcut(ptr);
713                 if ((shortcut->index_key[0] & ASSOC_ARRAY_FAN_MASK) != 0)
714                         goto not_this_keyring;
715 
716                 ptr = READ_ONCE(shortcut->next_node);
717                 node = assoc_array_ptr_to_node(ptr);
718                 goto begin_node;
719         }
720 
721         node = assoc_array_ptr_to_node(ptr);
722         ptr = node->slots[0];
723         if (!assoc_array_ptr_is_meta(ptr))
724                 goto begin_node;
725 
726 descend_to_node:
727         /* Descend to a more distal node in this keyring's content tree and go
728          * through that.
729          */
730         kdebug("descend");
731         if (assoc_array_ptr_is_shortcut(ptr)) {
732                 shortcut = assoc_array_ptr_to_shortcut(ptr);
733                 ptr = READ_ONCE(shortcut->next_node);
734                 BUG_ON(!assoc_array_ptr_is_node(ptr));
735         }
736         node = assoc_array_ptr_to_node(ptr);
737 
738 begin_node:
739         kdebug("begin_node");
740         slot = 0;
741 ascend_to_node:
742         /* Go through the slots in a node */
743         for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
744                 ptr = READ_ONCE(node->slots[slot]);
745 
746                 if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
747                         goto descend_to_node;
748 
749                 if (!keyring_ptr_is_keyring(ptr))
750                         continue;
751 
752                 key = keyring_ptr_to_key(ptr);
753 
754                 if (sp >= KEYRING_SEARCH_MAX_DEPTH) {
755                         if (ctx->flags & KEYRING_SEARCH_DETECT_TOO_DEEP) {
756                                 ctx->result = ERR_PTR(-ELOOP);
757                                 return false;
758                         }
759                         goto not_this_keyring;
760                 }
761 
762                 /* Search a nested keyring */
763                 if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
764                     key_task_permission(make_key_ref(key, ctx->possessed),
765                                         ctx->cred, KEY_NEED_SEARCH) < 0)
766                         continue;
767 
768                 /* stack the current position */
769                 stack[sp].keyring = keyring;
770                 stack[sp].node = node;
771                 stack[sp].slot = slot;
772                 sp++;
773 
774                 /* begin again with the new keyring */
775                 keyring = key;
776                 goto descend_to_keyring;
777         }
778 
779         /* We've dealt with all the slots in the current node, so now we need
780          * to ascend to the parent and continue processing there.
781          */
782         ptr = READ_ONCE(node->back_pointer);
783         slot = node->parent_slot;
784 
785         if (ptr && assoc_array_ptr_is_shortcut(ptr)) {
786                 shortcut = assoc_array_ptr_to_shortcut(ptr);
787                 ptr = READ_ONCE(shortcut->back_pointer);
788                 slot = shortcut->parent_slot;
789         }
790         if (!ptr)
791                 goto not_this_keyring;
792         node = assoc_array_ptr_to_node(ptr);
793         slot++;
794 
795         /* If we've ascended to the root (zero backpointer), we must have just
796          * finished processing the leftmost branch rather than the root slots -
797          * so there can't be any more keyrings for us to find.
798          */
799         if (node->back_pointer) {
800                 kdebug("ascend %d", slot);
801                 goto ascend_to_node;
802         }
803 
804         /* The keyring we're looking at was disqualified or didn't contain a
805          * matching key.
806          */
807 not_this_keyring:
808         kdebug("not_this_keyring %d", sp);
809         if (sp <= 0) {
810                 kleave(" = false");
811                 return false;
812         }
813 
814         /* Resume the processing of a keyring higher up in the tree */
815         sp--;
816         keyring = stack[sp].keyring;
817         node = stack[sp].node;
818         slot = stack[sp].slot + 1;
819         kdebug("ascend to %d [%d]", keyring->serial, slot);
820         goto ascend_to_node;
821 
822         /* We found a viable match */
823 found:
824         key = key_ref_to_ptr(ctx->result);
825         key_check(key);
826         if (!(ctx->flags & KEYRING_SEARCH_NO_UPDATE_TIME)) {
827                 key->last_used_at = ctx->now;
828                 keyring->last_used_at = ctx->now;
829                 while (sp > 0)
830                         stack[--sp].keyring->last_used_at = ctx->now;
831         }
832         kleave(" = true");
833         return true;
834 }
835 
836 /**
837  * keyring_search_aux - Search a keyring tree for a key matching some criteria
838  * @keyring_ref: A pointer to the keyring with possession indicator.
839  * @ctx: The keyring search context.
840  *
841  * Search the supplied keyring tree for a key that matches the criteria given.
842  * The root keyring and any linked keyrings must grant Search permission to the
843  * caller to be searchable and keys can only be found if they too grant Search
844  * to the caller. The possession flag on the root keyring pointer controls use
845  * of the possessor bits in permissions checking of the entire tree.  In
846  * addition, the LSM gets to forbid keyring searches and key matches.
847  *
848  * The search is performed as a breadth-then-depth search up to the prescribed
849  * limit (KEYRING_SEARCH_MAX_DEPTH).
850  *
851  * Keys are matched to the type provided and are then filtered by the match
852  * function, which is given the description to use in any way it sees fit.  The
853  * match function may use any attributes of a key that it wishes to to
854  * determine the match.  Normally the match function from the key type would be
855  * used.
856  *
857  * RCU can be used to prevent the keyring key lists from disappearing without
858  * the need to take lots of locks.
859  *
860  * Returns a pointer to the found key and increments the key usage count if
861  * successful; -EAGAIN if no matching keys were found, or if expired or revoked
862  * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
863  * specified keyring wasn't a keyring.
864  *
865  * In the case of a successful return, the possession attribute from
866  * @keyring_ref is propagated to the returned key reference.
867  */
868 key_ref_t keyring_search_aux(key_ref_t keyring_ref,
869                              struct keyring_search_context *ctx)
870 {
871         struct key *keyring;
872         long err;
873 
874         ctx->iterator = keyring_search_iterator;
875         ctx->possessed = is_key_possessed(keyring_ref);
876         ctx->result = ERR_PTR(-EAGAIN);
877 
878         keyring = key_ref_to_ptr(keyring_ref);
879         key_check(keyring);
880 
881         if (keyring->type != &key_type_keyring)
882                 return ERR_PTR(-ENOTDIR);
883 
884         if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM)) {
885                 err = key_task_permission(keyring_ref, ctx->cred, KEY_NEED_SEARCH);
886                 if (err < 0)
887                         return ERR_PTR(err);
888         }
889 
890         rcu_read_lock();
891         ctx->now = ktime_get_real_seconds();
892         if (search_nested_keyrings(keyring, ctx))
893                 __key_get(key_ref_to_ptr(ctx->result));
894         rcu_read_unlock();
895         return ctx->result;
896 }
897 
898 /**
899  * keyring_search - Search the supplied keyring tree for a matching key
900  * @keyring: The root of the keyring tree to be searched.
901  * @type: The type of keyring we want to find.
902  * @description: The name of the keyring we want to find.
903  *
904  * As keyring_search_aux() above, but using the current task's credentials and
905  * type's default matching function and preferred search method.
906  */
907 key_ref_t keyring_search(key_ref_t keyring,
908                          struct key_type *type,
909                          const char *description)
910 {
911         struct keyring_search_context ctx = {
912                 .index_key.type         = type,
913                 .index_key.description  = description,
914                 .index_key.desc_len     = strlen(description),
915                 .cred                   = current_cred(),
916                 .match_data.cmp         = key_default_cmp,
917                 .match_data.raw_data    = description,
918                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
919                 .flags                  = KEYRING_SEARCH_DO_STATE_CHECK,
920         };
921         key_ref_t key;
922         int ret;
923 
924         if (type->match_preparse) {
925                 ret = type->match_preparse(&ctx.match_data);
926                 if (ret < 0)
927                         return ERR_PTR(ret);
928         }
929 
930         key = keyring_search_aux(keyring, &ctx);
931 
932         if (type->match_free)
933                 type->match_free(&ctx.match_data);
934         return key;
935 }
936 EXPORT_SYMBOL(keyring_search);
937 
938 static struct key_restriction *keyring_restriction_alloc(
939         key_restrict_link_func_t check)
940 {
941         struct key_restriction *keyres =
942                 kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
943 
944         if (!keyres)
945                 return ERR_PTR(-ENOMEM);
946 
947         keyres->check = check;
948 
949         return keyres;
950 }
951 
952 /*
953  * Semaphore to serialise restriction setup to prevent reference count
954  * cycles through restriction key pointers.
955  */
956 static DECLARE_RWSEM(keyring_serialise_restrict_sem);
957 
958 /*
959  * Check for restriction cycles that would prevent keyring garbage collection.
960  * keyring_serialise_restrict_sem must be held.
961  */
962 static bool keyring_detect_restriction_cycle(const struct key *dest_keyring,
963                                              struct key_restriction *keyres)
964 {
965         while (keyres && keyres->key &&
966                keyres->key->type == &key_type_keyring) {
967                 if (keyres->key == dest_keyring)
968                         return true;
969 
970                 keyres = keyres->key->restrict_link;
971         }
972 
973         return false;
974 }
975 
976 /**
977  * keyring_restrict - Look up and apply a restriction to a keyring
978  *
979  * @keyring: The keyring to be restricted
980  * @restriction: The restriction options to apply to the keyring
981  */
982 int keyring_restrict(key_ref_t keyring_ref, const char *type,
983                      const char *restriction)
984 {
985         struct key *keyring;
986         struct key_type *restrict_type = NULL;
987         struct key_restriction *restrict_link;
988         int ret = 0;
989 
990         keyring = key_ref_to_ptr(keyring_ref);
991         key_check(keyring);
992 
993         if (keyring->type != &key_type_keyring)
994                 return -ENOTDIR;
995 
996         if (!type) {
997                 restrict_link = keyring_restriction_alloc(restrict_link_reject);
998         } else {
999                 restrict_type = key_type_lookup(type);
1000 
1001                 if (IS_ERR(restrict_type))
1002                         return PTR_ERR(restrict_type);
1003 
1004                 if (!restrict_type->lookup_restriction) {
1005                         ret = -ENOENT;
1006                         goto error;
1007                 }
1008 
1009                 restrict_link = restrict_type->lookup_restriction(restriction);
1010         }
1011 
1012         if (IS_ERR(restrict_link)) {
1013                 ret = PTR_ERR(restrict_link);
1014                 goto error;
1015         }
1016 
1017         down_write(&keyring->sem);
1018         down_write(&keyring_serialise_restrict_sem);
1019 
1020         if (keyring->restrict_link)
1021                 ret = -EEXIST;
1022         else if (keyring_detect_restriction_cycle(keyring, restrict_link))
1023                 ret = -EDEADLK;
1024         else
1025                 keyring->restrict_link = restrict_link;
1026 
1027         up_write(&keyring_serialise_restrict_sem);
1028         up_write(&keyring->sem);
1029 
1030         if (ret < 0) {
1031                 key_put(restrict_link->key);
1032                 kfree(restrict_link);
1033         }
1034 
1035 error:
1036         if (restrict_type)
1037                 key_type_put(restrict_type);
1038 
1039         return ret;
1040 }
1041 EXPORT_SYMBOL(keyring_restrict);
1042 
1043 /*
1044  * Search the given keyring for a key that might be updated.
1045  *
1046  * The caller must guarantee that the keyring is a keyring and that the
1047  * permission is granted to modify the keyring as no check is made here.  The
1048  * caller must also hold a lock on the keyring semaphore.
1049  *
1050  * Returns a pointer to the found key with usage count incremented if
1051  * successful and returns NULL if not found.  Revoked and invalidated keys are
1052  * skipped over.
1053  *
1054  * If successful, the possession indicator is propagated from the keyring ref
1055  * to the returned key reference.
1056  */
1057 key_ref_t find_key_to_update(key_ref_t keyring_ref,
1058                              const struct keyring_index_key *index_key)
1059 {
1060         struct key *keyring, *key;
1061         const void *object;
1062 
1063         keyring = key_ref_to_ptr(keyring_ref);
1064 
1065         kenter("{%d},{%s,%s}",
1066                keyring->serial, index_key->type->name, index_key->description);
1067 
1068         object = assoc_array_find(&keyring->keys, &keyring_assoc_array_ops,
1069                                   index_key);
1070 
1071         if (object)
1072                 goto found;
1073 
1074         kleave(" = NULL");
1075         return NULL;
1076 
1077 found:
1078         key = keyring_ptr_to_key(object);
1079         if (key->flags & ((1 << KEY_FLAG_INVALIDATED) |
1080                           (1 << KEY_FLAG_REVOKED))) {
1081                 kleave(" = NULL [x]");
1082                 return NULL;
1083         }
1084         __key_get(key);
1085         kleave(" = {%d}", key->serial);
1086         return make_key_ref(key, is_key_possessed(keyring_ref));
1087 }
1088 
1089 /*
1090  * Find a keyring with the specified name.
1091  *
1092  * Only keyrings that have nonzero refcount, are not revoked, and are owned by a
1093  * user in the current user namespace are considered.  If @uid_keyring is %true,
1094  * the keyring additionally must have been allocated as a user or user session
1095  * keyring; otherwise, it must grant Search permission directly to the caller.
1096  *
1097  * Returns a pointer to the keyring with the keyring's refcount having being
1098  * incremented on success.  -ENOKEY is returned if a key could not be found.
1099  */
1100 struct key *find_keyring_by_name(const char *name, bool uid_keyring)
1101 {
1102         struct key *keyring;
1103         int bucket;
1104 
1105         if (!name)
1106                 return ERR_PTR(-EINVAL);
1107 
1108         bucket = keyring_hash(name);
1109 
1110         read_lock(&keyring_name_lock);
1111 
1112         if (keyring_name_hash[bucket].next) {
1113                 /* search this hash bucket for a keyring with a matching name
1114                  * that's readable and that hasn't been revoked */
1115                 list_for_each_entry(keyring,
1116                                     &keyring_name_hash[bucket],
1117                                     name_link
1118                                     ) {
1119                         if (!kuid_has_mapping(current_user_ns(), keyring->user->uid))
1120                                 continue;
1121 
1122                         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
1123                                 continue;
1124 
1125                         if (strcmp(keyring->description, name) != 0)
1126                                 continue;
1127 
1128                         if (uid_keyring) {
1129                                 if (!test_bit(KEY_FLAG_UID_KEYRING,
1130                                               &keyring->flags))
1131                                         continue;
1132                         } else {
1133                                 if (key_permission(make_key_ref(keyring, 0),
1134                                                    KEY_NEED_SEARCH) < 0)
1135                                         continue;
1136                         }
1137 
1138                         /* we've got a match but we might end up racing with
1139                          * key_cleanup() if the keyring is currently 'dead'
1140                          * (ie. it has a zero usage count) */
1141                         if (!refcount_inc_not_zero(&keyring->usage))
1142                                 continue;
1143                         keyring->last_used_at = ktime_get_real_seconds();
1144                         goto out;
1145                 }
1146         }
1147 
1148         keyring = ERR_PTR(-ENOKEY);
1149 out:
1150         read_unlock(&keyring_name_lock);
1151         return keyring;
1152 }
1153 
1154 static int keyring_detect_cycle_iterator(const void *object,
1155                                          void *iterator_data)
1156 {
1157         struct keyring_search_context *ctx = iterator_data;
1158         const struct key *key = keyring_ptr_to_key(object);
1159 
1160         kenter("{%d}", key->serial);
1161 
1162         /* We might get a keyring with matching index-key that is nonetheless a
1163          * different keyring. */
1164         if (key != ctx->match_data.raw_data)
1165                 return 0;
1166 
1167         ctx->result = ERR_PTR(-EDEADLK);
1168         return 1;
1169 }
1170 
1171 /*
1172  * See if a cycle will will be created by inserting acyclic tree B in acyclic
1173  * tree A at the topmost level (ie: as a direct child of A).
1174  *
1175  * Since we are adding B to A at the top level, checking for cycles should just
1176  * be a matter of seeing if node A is somewhere in tree B.
1177  */
1178 static int keyring_detect_cycle(struct key *A, struct key *B)
1179 {
1180         struct keyring_search_context ctx = {
1181                 .index_key              = A->index_key,
1182                 .match_data.raw_data    = A,
1183                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
1184                 .iterator               = keyring_detect_cycle_iterator,
1185                 .flags                  = (KEYRING_SEARCH_NO_STATE_CHECK |
1186                                            KEYRING_SEARCH_NO_UPDATE_TIME |
1187                                            KEYRING_SEARCH_NO_CHECK_PERM |
1188                                            KEYRING_SEARCH_DETECT_TOO_DEEP),
1189         };
1190 
1191         rcu_read_lock();
1192         search_nested_keyrings(B, &ctx);
1193         rcu_read_unlock();
1194         return PTR_ERR(ctx.result) == -EAGAIN ? 0 : PTR_ERR(ctx.result);
1195 }
1196 
1197 /*
1198  * Preallocate memory so that a key can be linked into to a keyring.
1199  */
1200 int __key_link_begin(struct key *keyring,
1201                      const struct keyring_index_key *index_key,
1202                      struct assoc_array_edit **_edit)
1203         __acquires(&keyring->sem)
1204         __acquires(&keyring_serialise_link_sem)
1205 {
1206         struct assoc_array_edit *edit;
1207         int ret;
1208 
1209         kenter("%d,%s,%s,",
1210                keyring->serial, index_key->type->name, index_key->description);
1211 
1212         BUG_ON(index_key->desc_len == 0);
1213 
1214         if (keyring->type != &key_type_keyring)
1215                 return -ENOTDIR;
1216 
1217         down_write(&keyring->sem);
1218 
1219         ret = -EKEYREVOKED;
1220         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
1221                 goto error_krsem;
1222 
1223         /* serialise link/link calls to prevent parallel calls causing a cycle
1224          * when linking two keyring in opposite orders */
1225         if (index_key->type == &key_type_keyring)
1226                 down_write(&keyring_serialise_link_sem);
1227 
1228         /* Create an edit script that will insert/replace the key in the
1229          * keyring tree.
1230          */
1231         edit = assoc_array_insert(&keyring->keys,
1232                                   &keyring_assoc_array_ops,
1233                                   index_key,
1234                                   NULL);
1235         if (IS_ERR(edit)) {
1236                 ret = PTR_ERR(edit);
1237                 goto error_sem;
1238         }
1239 
1240         /* If we're not replacing a link in-place then we're going to need some
1241          * extra quota.
1242          */
1243         if (!edit->dead_leaf) {
1244                 ret = key_payload_reserve(keyring,
1245                                           keyring->datalen + KEYQUOTA_LINK_BYTES);
1246                 if (ret < 0)
1247                         goto error_cancel;
1248         }
1249 
1250         *_edit = edit;
1251         kleave(" = 0");
1252         return 0;
1253 
1254 error_cancel:
1255         assoc_array_cancel_edit(edit);
1256 error_sem:
1257         if (index_key->type == &key_type_keyring)
1258                 up_write(&keyring_serialise_link_sem);
1259 error_krsem:
1260         up_write(&keyring->sem);
1261         kleave(" = %d", ret);
1262         return ret;
1263 }
1264 
1265 /*
1266  * Check already instantiated keys aren't going to be a problem.
1267  *
1268  * The caller must have called __key_link_begin(). Don't need to call this for
1269  * keys that were created since __key_link_begin() was called.
1270  */
1271 int __key_link_check_live_key(struct key *keyring, struct key *key)
1272 {
1273         if (key->type == &key_type_keyring)
1274                 /* check that we aren't going to create a cycle by linking one
1275                  * keyring to another */
1276                 return keyring_detect_cycle(keyring, key);
1277         return 0;
1278 }
1279 
1280 /*
1281  * Link a key into to a keyring.
1282  *
1283  * Must be called with __key_link_begin() having being called.  Discards any
1284  * already extant link to matching key if there is one, so that each keyring
1285  * holds at most one link to any given key of a particular type+description
1286  * combination.
1287  */
1288 void __key_link(struct key *key, struct assoc_array_edit **_edit)
1289 {
1290         __key_get(key);
1291         assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key));
1292         assoc_array_apply_edit(*_edit);
1293         *_edit = NULL;
1294 }
1295 
1296 /*
1297  * Finish linking a key into to a keyring.
1298  *
1299  * Must be called with __key_link_begin() having being called.
1300  */
1301 void __key_link_end(struct key *keyring,
1302                     const struct keyring_index_key *index_key,
1303                     struct assoc_array_edit *edit)
1304         __releases(&keyring->sem)
1305         __releases(&keyring_serialise_link_sem)
1306 {
1307         BUG_ON(index_key->type == NULL);
1308         kenter("%d,%s,", keyring->serial, index_key->type->name);
1309 
1310         if (index_key->type == &key_type_keyring)
1311                 up_write(&keyring_serialise_link_sem);
1312 
1313         if (edit) {
1314                 if (!edit->dead_leaf) {
1315                         key_payload_reserve(keyring,
1316                                 keyring->datalen - KEYQUOTA_LINK_BYTES);
1317                 }
1318                 assoc_array_cancel_edit(edit);
1319         }
1320         up_write(&keyring->sem);
1321 }
1322 
1323 /*
1324  * Check addition of keys to restricted keyrings.
1325  */
1326 static int __key_link_check_restriction(struct key *keyring, struct key *key)
1327 {
1328         if (!keyring->restrict_link || !keyring->restrict_link->check)
1329                 return 0;
1330         return keyring->restrict_link->check(keyring, key->type, &key->payload,
1331                                              keyring->restrict_link->key);
1332 }
1333 
1334 /**
1335  * key_link - Link a key to a keyring
1336  * @keyring: The keyring to make the link in.
1337  * @key: The key to link to.
1338  *
1339  * Make a link in a keyring to a key, such that the keyring holds a reference
1340  * on that key and the key can potentially be found by searching that keyring.
1341  *
1342  * This function will write-lock the keyring's semaphore and will consume some
1343  * of the user's key data quota to hold the link.
1344  *
1345  * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
1346  * -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
1347  * full, -EDQUOT if there is insufficient key data quota remaining to add
1348  * another link or -ENOMEM if there's insufficient memory.
1349  *
1350  * It is assumed that the caller has checked that it is permitted for a link to
1351  * be made (the keyring should have Write permission and the key Link
1352  * permission).
1353  */
1354 int key_link(struct key *keyring, struct key *key)
1355 {
1356         struct assoc_array_edit *edit;
1357         int ret;
1358 
1359         kenter("{%d,%d}", keyring->serial, refcount_read(&keyring->usage));
1360 
1361         key_check(keyring);
1362         key_check(key);
1363 
1364         ret = __key_link_begin(keyring, &key->index_key, &edit);
1365         if (ret == 0) {
1366                 kdebug("begun {%d,%d}", keyring->serial, refcount_read(&keyring->usage));
1367                 ret = __key_link_check_restriction(keyring, key);
1368                 if (ret == 0)
1369                         ret = __key_link_check_live_key(keyring, key);
1370                 if (ret == 0)
1371                         __key_link(key, &edit);
1372                 __key_link_end(keyring, &key->index_key, edit);
1373         }
1374 
1375         kleave(" = %d {%d,%d}", ret, keyring->serial, refcount_read(&keyring->usage));
1376         return ret;
1377 }
1378 EXPORT_SYMBOL(key_link);
1379 
1380 /**
1381  * key_unlink - Unlink the first link to a key from a keyring.
1382  * @keyring: The keyring to remove the link from.
1383  * @key: The key the link is to.
1384  *
1385  * Remove a link from a keyring to a key.
1386  *
1387  * This function will write-lock the keyring's semaphore.
1388  *
1389  * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
1390  * the key isn't linked to by the keyring or -ENOMEM if there's insufficient
1391  * memory.
1392  *
1393  * It is assumed that the caller has checked that it is permitted for a link to
1394  * be removed (the keyring should have Write permission; no permissions are
1395  * required on the key).
1396  */
1397 int key_unlink(struct key *keyring, struct key *key)
1398 {
1399         struct assoc_array_edit *edit;
1400         int ret;
1401 
1402         key_check(keyring);
1403         key_check(key);
1404 
1405         if (keyring->type != &key_type_keyring)
1406                 return -ENOTDIR;
1407 
1408         down_write(&keyring->sem);
1409 
1410         edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops,
1411                                   &key->index_key);
1412         if (IS_ERR(edit)) {
1413                 ret = PTR_ERR(edit);
1414                 goto error;
1415         }
1416         ret = -ENOENT;
1417         if (edit == NULL)
1418                 goto error;
1419 
1420         assoc_array_apply_edit(edit);
1421         key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES);
1422         ret = 0;
1423 
1424 error:
1425         up_write(&keyring->sem);
1426         return ret;
1427 }
1428 EXPORT_SYMBOL(key_unlink);
1429 
1430 /**
1431  * keyring_clear - Clear a keyring
1432  * @keyring: The keyring to clear.
1433  *
1434  * Clear the contents of the specified keyring.
1435  *
1436  * Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
1437  */
1438 int keyring_clear(struct key *keyring)
1439 {
1440         struct assoc_array_edit *edit;
1441         int ret;
1442 
1443         if (keyring->type != &key_type_keyring)
1444                 return -ENOTDIR;
1445 
1446         down_write(&keyring->sem);
1447 
1448         edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
1449         if (IS_ERR(edit)) {
1450                 ret = PTR_ERR(edit);
1451         } else {
1452                 if (edit)
1453                         assoc_array_apply_edit(edit);
1454                 key_payload_reserve(keyring, 0);
1455                 ret = 0;
1456         }
1457 
1458         up_write(&keyring->sem);
1459         return ret;
1460 }
1461 EXPORT_SYMBOL(keyring_clear);
1462 
1463 /*
1464  * Dispose of the links from a revoked keyring.
1465  *
1466  * This is called with the key sem write-locked.
1467  */
1468 static void keyring_revoke(struct key *keyring)
1469 {
1470         struct assoc_array_edit *edit;
1471 
1472         edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
1473         if (!IS_ERR(edit)) {
1474                 if (edit)
1475                         assoc_array_apply_edit(edit);
1476                 key_payload_reserve(keyring, 0);
1477         }
1478 }
1479 
1480 static bool keyring_gc_select_iterator(void *object, void *iterator_data)
1481 {
1482         struct key *key = keyring_ptr_to_key(object);
1483         time64_t *limit = iterator_data;
1484 
1485         if (key_is_dead(key, *limit))
1486                 return false;
1487         key_get(key);
1488         return true;
1489 }
1490 
1491 static int keyring_gc_check_iterator(const void *object, void *iterator_data)
1492 {
1493         const struct key *key = keyring_ptr_to_key(object);
1494         time64_t *limit = iterator_data;
1495 
1496         key_check(key);
1497         return key_is_dead(key, *limit);
1498 }
1499 
1500 /*
1501  * Garbage collect pointers from a keyring.
1502  *
1503  * Not called with any locks held.  The keyring's key struct will not be
1504  * deallocated under us as only our caller may deallocate it.
1505  */
1506 void keyring_gc(struct key *keyring, time64_t limit)
1507 {
1508         int result;
1509 
1510         kenter("%x{%s}", keyring->serial, keyring->description ?: "");
1511 
1512         if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
1513                               (1 << KEY_FLAG_REVOKED)))
1514                 goto dont_gc;
1515 
1516         /* scan the keyring looking for dead keys */
1517         rcu_read_lock();
1518         result = assoc_array_iterate(&keyring->keys,
1519                                      keyring_gc_check_iterator, &limit);
1520         rcu_read_unlock();
1521         if (result == true)
1522                 goto do_gc;
1523 
1524 dont_gc:
1525         kleave(" [no gc]");
1526         return;
1527 
1528 do_gc:
1529         down_write(&keyring->sem);
1530         assoc_array_gc(&keyring->keys, &keyring_assoc_array_ops,
1531                        keyring_gc_select_iterator, &limit);
1532         up_write(&keyring->sem);
1533         kleave(" [gc]");
1534 }
1535 
1536 /*
1537  * Garbage collect restriction pointers from a keyring.
1538  *
1539  * Keyring restrictions are associated with a key type, and must be cleaned
1540  * up if the key type is unregistered. The restriction is altered to always
1541  * reject additional keys so a keyring cannot be opened up by unregistering
1542  * a key type.
1543  *
1544  * Not called with any keyring locks held. The keyring's key struct will not
1545  * be deallocated under us as only our caller may deallocate it.
1546  *
1547  * The caller is required to hold key_types_sem and dead_type->sem. This is
1548  * fulfilled by key_gc_keytype() holding the locks on behalf of
1549  * key_garbage_collector(), which it invokes on a workqueue.
1550  */
1551 void keyring_restriction_gc(struct key *keyring, struct key_type *dead_type)
1552 {
1553         struct key_restriction *keyres;
1554 
1555         kenter("%x{%s}", keyring->serial, keyring->description ?: "");
1556 
1557         /*
1558          * keyring->restrict_link is only assigned at key allocation time
1559          * or with the key type locked, so the only values that could be
1560          * concurrently assigned to keyring->restrict_link are for key
1561          * types other than dead_type. Given this, it's ok to check
1562          * the key type before acquiring keyring->sem.
1563          */
1564         if (!dead_type || !keyring->restrict_link ||
1565             keyring->restrict_link->keytype != dead_type) {
1566                 kleave(" [no restriction gc]");
1567                 return;
1568         }
1569 
1570         /* Lock the keyring to ensure that a link is not in progress */
1571         down_write(&keyring->sem);
1572 
1573         keyres = keyring->restrict_link;
1574 
1575         keyres->check = restrict_link_reject;
1576 
1577         key_put(keyres->key);
1578         keyres->key = NULL;
1579         keyres->keytype = NULL;
1580 
1581         up_write(&keyring->sem);
1582 
1583         kleave(" [restriction gc]");
1584 }
1585 

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