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
  42static inline bool keyring_ptr_is_keyring(const struct assoc_array_ptr *x)
  43{
  44	return (unsigned long)x & KEYRING_PTR_SUBTYPE;
  45}
  46static 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}
  51static 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
  58static struct list_head	keyring_name_hash[KEYRING_NAME_HASH_SIZE];
  59static DEFINE_RWLOCK(keyring_name_lock);
  60
  61static 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 */
  76static int keyring_preparse(struct key_preparsed_payload *prep);
  77static void keyring_free_preparse(struct key_preparsed_payload *prep);
  78static int keyring_instantiate(struct key *keyring,
  79			       struct key_preparsed_payload *prep);
  80static void keyring_revoke(struct key *keyring);
  81static void keyring_destroy(struct key *keyring);
  82static void keyring_describe(const struct key *keyring, struct seq_file *m);
  83static long keyring_read(const struct key *keyring,
  84			 char __user *buffer, size_t buflen);
  85
  86struct 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};
  97EXPORT_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 */
 103static 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 */
 109static 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 */
 131static 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 */
 139static 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 */
 148static 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 */
 161static 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 */
 171static 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 */
 230static 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
 272static 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
 278static 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 */
 293static 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
 347same:
 348	return -1;
 349
 350differ_plus_i:
 351	level += i;
 352differ:
 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 */
 360static 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 */
 368static 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 */
 385static 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	assoc_array_destroy(&keyring->keys, &keyring_assoc_array_ops);
 398}
 399
 400/*
 401 * Describe a keyring for /proc.
 402 */
 403static 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
 418struct keyring_read_iterator_context {
 419	size_t			qty;
 420	size_t			count;
 421	key_serial_t __user	*buffer;
 422};
 423
 424static 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 */
 451static 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 */
 492struct 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}
 511EXPORT_SYMBOL(keyring_alloc);
 512
 513/*
 514 * By default, we keys found by getting an exact match on their descriptions.
 515 */
 516bool 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 */
 525static 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->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
 586skipped:
 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 */
 595static 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 */
 612static 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 */
 658descend_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
 704descend_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
 717begin_node:
 718	kdebug("begin_node");
 719	smp_read_barrier_depends();
 720	slot = 0;
 721ascend_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	 */
 789not_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 */
 805found:
 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 */
 850key_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 */
 889key_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}
 917EXPORT_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 */
 933key_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
 953found:
 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 */
 976struct 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				    name_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);
1020out:
1021	read_unlock(&keyring_name_lock);
1022	return keyring;
1023}
1024
1025static 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 */
1049static 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 */
1071int __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
1125error_cancel:
1126	assoc_array_cancel_edit(edit);
1127error_sem:
1128	if (index_key->type == &key_type_keyring)
1129		up_write(&keyring_serialise_link_sem);
1130error_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 */
1142int __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 */
1159void __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 */
1172void __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 */
1214int 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}
1240EXPORT_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 */
1259int 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
1286error:
1287	up_write(&keyring->sem);
1288	return ret;
1289}
1290EXPORT_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 */
1300int 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}
1323EXPORT_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 */
1330static 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
1342static 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
1353static 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 */
1368void 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
1386dont_gc:
1387	kleave(" [no gc]");
1388	return;
1389
1390do_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}