1// SPDX-License-Identifier: GPL-2.0-or-later
   2/* Keyring handling
   3 *
   4 * Copyright (C) 2004-2005, 2008, 2013 Red Hat, Inc. All Rights Reserved.
   5 * Written by David Howells (dhowells@redhat.com)
   6 */
   7
   8#include <linux/export.h>
   9#include <linux/init.h>
  10#include <linux/sched.h>
  11#include <linux/slab.h>
  12#include <linux/security.h>
  13#include <linux/seq_file.h>
  14#include <linux/err.h>
  15#include <linux/user_namespace.h>
  16#include <linux/nsproxy.h>
  17#include <keys/keyring-type.h>
  18#include <keys/user-type.h>
  19#include <linux/assoc_array_priv.h>
  20#include <linux/uaccess.h>
  21#include <net/net_namespace.h>
  22#include "internal.h"
  23
  24/*
  25 * When plumbing the depths of the key tree, this sets a hard limit
  26 * set on how deep we're willing to go.
  27 */
  28#define KEYRING_SEARCH_MAX_DEPTH 6
  29
  30/*
  31 * We mark pointers we pass to the associative array with bit 1 set if
  32 * they're keyrings and clear otherwise.
  33 */
  34#define KEYRING_PTR_SUBTYPE	0x2UL
  35
  36static inline bool keyring_ptr_is_keyring(const struct assoc_array_ptr *x)
  37{
  38	return (unsigned long)x & KEYRING_PTR_SUBTYPE;
  39}
  40static inline struct key *keyring_ptr_to_key(const struct assoc_array_ptr *x)
  41{
  42	void *object = assoc_array_ptr_to_leaf(x);
  43	return (struct key *)((unsigned long)object & ~KEYRING_PTR_SUBTYPE);
  44}
  45static inline void *keyring_key_to_ptr(struct key *key)
  46{
  47	if (key->type == &key_type_keyring)
  48		return (void *)((unsigned long)key | KEYRING_PTR_SUBTYPE);
  49	return key;
  50}
  51
  52static DEFINE_RWLOCK(keyring_name_lock);
  53
  54/*
  55 * Clean up the bits of user_namespace that belong to us.
  56 */
  57void key_free_user_ns(struct user_namespace *ns)
  58{
  59	write_lock(&keyring_name_lock);
  60	list_del_init(&ns->keyring_name_list);
  61	write_unlock(&keyring_name_lock);
  62
  63	key_put(ns->user_keyring_register);
  64#ifdef CONFIG_PERSISTENT_KEYRINGS
  65	key_put(ns->persistent_keyring_register);
  66#endif
  67}
  68
  69/*
  70 * The keyring key type definition.  Keyrings are simply keys of this type and
  71 * can be treated as ordinary keys in addition to having their own special
  72 * operations.
  73 */
  74static int keyring_preparse(struct key_preparsed_payload *prep);
  75static void keyring_free_preparse(struct key_preparsed_payload *prep);
  76static int keyring_instantiate(struct key *keyring,
  77			       struct key_preparsed_payload *prep);
  78static void keyring_revoke(struct key *keyring);
  79static void keyring_destroy(struct key *keyring);
  80static void keyring_describe(const struct key *keyring, struct seq_file *m);
  81static long keyring_read(const struct key *keyring,
  82			 char __user *buffer, size_t buflen);
  83
  84struct key_type key_type_keyring = {
  85	.name		= "keyring",
  86	.def_datalen	= 0,
  87	.preparse	= keyring_preparse,
  88	.free_preparse	= keyring_free_preparse,
  89	.instantiate	= keyring_instantiate,
  90	.revoke		= keyring_revoke,
  91	.destroy	= keyring_destroy,
  92	.describe	= keyring_describe,
  93	.read		= keyring_read,
  94};
  95EXPORT_SYMBOL(key_type_keyring);
  96
  97/*
  98 * Semaphore to serialise link/link calls to prevent two link calls in parallel
  99 * introducing a cycle.
 100 */
 101static DEFINE_MUTEX(keyring_serialise_link_lock);
 102
 103/*
 104 * Publish the name of a keyring so that it can be found by name (if it has
 105 * one and it doesn't begin with a dot).
 106 */
 107static void keyring_publish_name(struct key *keyring)
 108{
 109	struct user_namespace *ns = current_user_ns();
 110
 111	if (keyring->description &&
 112	    keyring->description[0] &&
 113	    keyring->description[0] != '.') {
 114		write_lock(&keyring_name_lock);
 115		list_add_tail(&keyring->name_link, &ns->keyring_name_list);
 116		write_unlock(&keyring_name_lock);
 117	}
 118}
 119
 120/*
 121 * Preparse a keyring payload
 122 */
 123static int keyring_preparse(struct key_preparsed_payload *prep)
 124{
 125	return prep->datalen != 0 ? -EINVAL : 0;
 126}
 127
 128/*
 129 * Free a preparse of a user defined key payload
 130 */
 131static void keyring_free_preparse(struct key_preparsed_payload *prep)
 132{
 133}
 134
 135/*
 136 * Initialise a keyring.
 137 *
 138 * Returns 0 on success, -EINVAL if given any data.
 139 */
 140static int keyring_instantiate(struct key *keyring,
 141			       struct key_preparsed_payload *prep)
 142{
 143	assoc_array_init(&keyring->keys);
 144	/* make the keyring available by name if it has one */
 145	keyring_publish_name(keyring);
 146	return 0;
 147}
 148
 149/*
 150 * Multiply 64-bits by 32-bits to 96-bits and fold back to 64-bit.  Ideally we'd
 151 * fold the carry back too, but that requires inline asm.
 152 */
 153static u64 mult_64x32_and_fold(u64 x, u32 y)
 154{
 155	u64 hi = (u64)(u32)(x >> 32) * y;
 156	u64 lo = (u64)(u32)(x) * y;
 157	return lo + ((u64)(u32)hi << 32) + (u32)(hi >> 32);
 158}
 159
 160/*
 161 * Hash a key type and description.
 162 */
 163static void hash_key_type_and_desc(struct keyring_index_key *index_key)
 164{
 165	const unsigned level_shift = ASSOC_ARRAY_LEVEL_STEP;
 166	const unsigned long fan_mask = ASSOC_ARRAY_FAN_MASK;
 167	const char *description = index_key->description;
 168	unsigned long hash, type;
 169	u32 piece;
 170	u64 acc;
 171	int n, desc_len = index_key->desc_len;
 172
 173	type = (unsigned long)index_key->type;
 174	acc = mult_64x32_and_fold(type, desc_len + 13);
 175	acc = mult_64x32_and_fold(acc, 9207);
 176	piece = (unsigned long)index_key->domain_tag;
 177	acc = mult_64x32_and_fold(acc, piece);
 178	acc = mult_64x32_and_fold(acc, 9207);
 179
 180	for (;;) {
 181		n = desc_len;
 182		if (n <= 0)
 183			break;
 184		if (n > 4)
 185			n = 4;
 186		piece = 0;
 187		memcpy(&piece, description, n);
 188		description += n;
 189		desc_len -= n;
 190		acc = mult_64x32_and_fold(acc, piece);
 191		acc = mult_64x32_and_fold(acc, 9207);
 192	}
 193
 194	/* Fold the hash down to 32 bits if need be. */
 195	hash = acc;
 196	if (ASSOC_ARRAY_KEY_CHUNK_SIZE == 32)
 197		hash ^= acc >> 32;
 198
 199	/* Squidge all the keyrings into a separate part of the tree to
 200	 * ordinary keys by making sure the lowest level segment in the hash is
 201	 * zero for keyrings and non-zero otherwise.
 202	 */
 203	if (index_key->type != &key_type_keyring && (hash & fan_mask) == 0)
 204		hash |= (hash >> (ASSOC_ARRAY_KEY_CHUNK_SIZE - level_shift)) | 1;
 205	else if (index_key->type == &key_type_keyring && (hash & fan_mask) != 0)
 206		hash = (hash + (hash << level_shift)) & ~fan_mask;
 207	index_key->hash = hash;
 208}
 209
 210/*
 211 * Finalise an index key to include a part of the description actually in the
 212 * index key, to set the domain tag and to calculate the hash.
 213 */
 214void key_set_index_key(struct keyring_index_key *index_key)
 215{
 216	static struct key_tag default_domain_tag = { .usage = REFCOUNT_INIT(1), };
 217	size_t n = min_t(size_t, index_key->desc_len, sizeof(index_key->desc));
 218
 219	memcpy(index_key->desc, index_key->description, n);
 220
 221	if (!index_key->domain_tag) {
 222		if (index_key->type->flags & KEY_TYPE_NET_DOMAIN)
 223			index_key->domain_tag = current->nsproxy->net_ns->key_domain;
 224		else
 225			index_key->domain_tag = &default_domain_tag;
 226	}
 227
 228	hash_key_type_and_desc(index_key);
 229}
 230
 231/**
 232 * key_put_tag - Release a ref on a tag.
 233 * @tag: The tag to release.
 234 *
 235 * This releases a reference the given tag and returns true if that ref was the
 236 * last one.
 237 */
 238bool key_put_tag(struct key_tag *tag)
 239{
 240	if (refcount_dec_and_test(&tag->usage)) {
 241		kfree_rcu(tag, rcu);
 242		return true;
 243	}
 244
 245	return false;
 246}
 247
 248/**
 249 * key_remove_domain - Kill off a key domain and gc its keys
 250 * @domain_tag: The domain tag to release.
 251 *
 252 * This marks a domain tag as being dead and releases a ref on it.  If that
 253 * wasn't the last reference, the garbage collector is poked to try and delete
 254 * all keys that were in the domain.
 255 */
 256void key_remove_domain(struct key_tag *domain_tag)
 257{
 258	domain_tag->removed = true;
 259	if (!key_put_tag(domain_tag))
 260		key_schedule_gc_links();
 261}
 262
 263/*
 264 * Build the next index key chunk.
 265 *
 266 * We return it one word-sized chunk at a time.
 267 */
 268static unsigned long keyring_get_key_chunk(const void *data, int level)
 269{
 270	const struct keyring_index_key *index_key = data;
 271	unsigned long chunk = 0;
 272	const u8 *d;
 273	int desc_len = index_key->desc_len, n = sizeof(chunk);
 274
 275	level /= ASSOC_ARRAY_KEY_CHUNK_SIZE;
 276	switch (level) {
 277	case 0:
 278		return index_key->hash;
 279	case 1:
 280		return index_key->x;
 281	case 2:
 282		return (unsigned long)index_key->type;
 283	case 3:
 284		return (unsigned long)index_key->domain_tag;
 285	default:
 286		level -= 4;
 287		if (desc_len <= sizeof(index_key->desc))
 288			return 0;
 289
 290		d = index_key->description + sizeof(index_key->desc);
 291		d += level * sizeof(long);
 292		desc_len -= sizeof(index_key->desc);
 293		if (desc_len > n)
 294			desc_len = n;
 295		do {
 296			chunk <<= 8;
 297			chunk |= *d++;
 298		} while (--desc_len > 0);
 299		return chunk;
 300	}
 301}
 302
 303static unsigned long keyring_get_object_key_chunk(const void *object, int level)
 304{
 305	const struct key *key = keyring_ptr_to_key(object);
 306	return keyring_get_key_chunk(&key->index_key, level);
 307}
 308
 309static bool keyring_compare_object(const void *object, const void *data)
 310{
 311	const struct keyring_index_key *index_key = data;
 312	const struct key *key = keyring_ptr_to_key(object);
 313
 314	return key->index_key.type == index_key->type &&
 315		key->index_key.domain_tag == index_key->domain_tag &&
 316		key->index_key.desc_len == index_key->desc_len &&
 317		memcmp(key->index_key.description, index_key->description,
 318		       index_key->desc_len) == 0;
 319}
 320
 321/*
 322 * Compare the index keys of a pair of objects and determine the bit position
 323 * at which they differ - if they differ.
 324 */
 325static int keyring_diff_objects(const void *object, const void *data)
 326{
 327	const struct key *key_a = keyring_ptr_to_key(object);
 328	const struct keyring_index_key *a = &key_a->index_key;
 329	const struct keyring_index_key *b = data;
 330	unsigned long seg_a, seg_b;
 331	int level, i;
 332
 333	level = 0;
 334	seg_a = a->hash;
 335	seg_b = b->hash;
 336	if ((seg_a ^ seg_b) != 0)
 337		goto differ;
 338	level += ASSOC_ARRAY_KEY_CHUNK_SIZE / 8;
 339
 340	/* The number of bits contributed by the hash is controlled by a
 341	 * constant in the assoc_array headers.  Everything else thereafter we
 342	 * can deal with as being machine word-size dependent.
 343	 */
 344	seg_a = a->x;
 345	seg_b = b->x;
 346	if ((seg_a ^ seg_b) != 0)
 347		goto differ;
 348	level += sizeof(unsigned long);
 349
 350	/* The next bit may not work on big endian */
 351	seg_a = (unsigned long)a->type;
 352	seg_b = (unsigned long)b->type;
 353	if ((seg_a ^ seg_b) != 0)
 354		goto differ;
 355	level += sizeof(unsigned long);
 356
 357	seg_a = (unsigned long)a->domain_tag;
 358	seg_b = (unsigned long)b->domain_tag;
 359	if ((seg_a ^ seg_b) != 0)
 360		goto differ;
 361	level += sizeof(unsigned long);
 362
 363	i = sizeof(a->desc);
 364	if (a->desc_len <= i)
 365		goto same;
 366
 367	for (; i < a->desc_len; i++) {
 368		seg_a = *(unsigned char *)(a->description + i);
 369		seg_b = *(unsigned char *)(b->description + i);
 370		if ((seg_a ^ seg_b) != 0)
 371			goto differ_plus_i;
 372	}
 373
 374same:
 375	return -1;
 376
 377differ_plus_i:
 378	level += i;
 379differ:
 380	i = level * 8 + __ffs(seg_a ^ seg_b);
 381	return i;
 382}
 383
 384/*
 385 * Free an object after stripping the keyring flag off of the pointer.
 386 */
 387static void keyring_free_object(void *object)
 388{
 389	key_put(keyring_ptr_to_key(object));
 390}
 391
 392/*
 393 * Operations for keyring management by the index-tree routines.
 394 */
 395static const struct assoc_array_ops keyring_assoc_array_ops = {
 396	.get_key_chunk		= keyring_get_key_chunk,
 397	.get_object_key_chunk	= keyring_get_object_key_chunk,
 398	.compare_object		= keyring_compare_object,
 399	.diff_objects		= keyring_diff_objects,
 400	.free_object		= keyring_free_object,
 401};
 402
 403/*
 404 * Clean up a keyring when it is destroyed.  Unpublish its name if it had one
 405 * and dispose of its data.
 406 *
 407 * The garbage collector detects the final key_put(), removes the keyring from
 408 * the serial number tree and then does RCU synchronisation before coming here,
 409 * so we shouldn't need to worry about code poking around here with the RCU
 410 * readlock held by this time.
 411 */
 412static void keyring_destroy(struct key *keyring)
 413{
 414	if (keyring->description) {
 415		write_lock(&keyring_name_lock);
 416
 417		if (keyring->name_link.next != NULL &&
 418		    !list_empty(&keyring->name_link))
 419			list_del(&keyring->name_link);
 420
 421		write_unlock(&keyring_name_lock);
 422	}
 423
 424	if (keyring->restrict_link) {
 425		struct key_restriction *keyres = keyring->restrict_link;
 426
 427		key_put(keyres->key);
 428		kfree(keyres);
 429	}
 430
 431	assoc_array_destroy(&keyring->keys, &keyring_assoc_array_ops);
 432}
 433
 434/*
 435 * Describe a keyring for /proc.
 436 */
 437static void keyring_describe(const struct key *keyring, struct seq_file *m)
 438{
 439	if (keyring->description)
 440		seq_puts(m, keyring->description);
 441	else
 442		seq_puts(m, "[anon]");
 443
 444	if (key_is_positive(keyring)) {
 445		if (keyring->keys.nr_leaves_on_tree != 0)
 446			seq_printf(m, ": %lu", keyring->keys.nr_leaves_on_tree);
 447		else
 448			seq_puts(m, ": empty");
 449	}
 450}
 451
 452struct keyring_read_iterator_context {
 453	size_t			buflen;
 454	size_t			count;
 455	key_serial_t __user	*buffer;
 456};
 457
 458static int keyring_read_iterator(const void *object, void *data)
 459{
 460	struct keyring_read_iterator_context *ctx = data;
 461	const struct key *key = keyring_ptr_to_key(object);
 
 462
 463	kenter("{%s,%d},,{%zu/%zu}",
 464	       key->type->name, key->serial, ctx->count, ctx->buflen);
 465
 466	if (ctx->count >= ctx->buflen)
 467		return 1;
 468
 469	*ctx->buffer++ = key->serial;
 
 
 
 470	ctx->count += sizeof(key->serial);
 471	return 0;
 472}
 473
 474/*
 475 * Read a list of key IDs from the keyring's contents in binary form
 476 *
 477 * The keyring's semaphore is read-locked by the caller.  This prevents someone
 478 * from modifying it under us - which could cause us to read key IDs multiple
 479 * times.
 480 */
 481static long keyring_read(const struct key *keyring,
 482			 char __user *buffer, size_t buflen)
 483{
 484	struct keyring_read_iterator_context ctx;
 485	long ret;
 486
 487	kenter("{%d},,%zu", key_serial(keyring), buflen);
 488
 489	if (buflen & (sizeof(key_serial_t) - 1))
 490		return -EINVAL;
 491
 492	/* Copy as many key IDs as fit into the buffer */
 493	if (buffer && buflen) {
 494		ctx.buffer = (key_serial_t __user *)buffer;
 495		ctx.buflen = buflen;
 496		ctx.count = 0;
 497		ret = assoc_array_iterate(&keyring->keys,
 498					  keyring_read_iterator, &ctx);
 499		if (ret < 0) {
 500			kleave(" = %ld [iterate]", ret);
 501			return ret;
 502		}
 503	}
 504
 505	/* Return the size of the buffer needed */
 506	ret = keyring->keys.nr_leaves_on_tree * sizeof(key_serial_t);
 507	if (ret <= buflen)
 508		kleave("= %ld [ok]", ret);
 509	else
 510		kleave("= %ld [buffer too small]", ret);
 511	return ret;
 512}
 513
 514/*
 515 * Allocate a keyring and link into the destination keyring.
 516 */
 517struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
 518			  const struct cred *cred, key_perm_t perm,
 519			  unsigned long flags,
 520			  struct key_restriction *restrict_link,
 521			  struct key *dest)
 522{
 523	struct key *keyring;
 524	int ret;
 525
 526	keyring = key_alloc(&key_type_keyring, description,
 527			    uid, gid, cred, perm, flags, restrict_link);
 528	if (!IS_ERR(keyring)) {
 529		ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
 530		if (ret < 0) {
 531			key_put(keyring);
 532			keyring = ERR_PTR(ret);
 533		}
 534	}
 535
 536	return keyring;
 537}
 538EXPORT_SYMBOL(keyring_alloc);
 539
 540/**
 541 * restrict_link_reject - Give -EPERM to restrict link
 542 * @keyring: The keyring being added to.
 543 * @type: The type of key being added.
 544 * @payload: The payload of the key intended to be added.
 545 * @restriction_key: Keys providing additional data for evaluating restriction.
 546 *
 547 * Reject the addition of any links to a keyring.  It can be overridden by
 548 * passing KEY_ALLOC_BYPASS_RESTRICTION to key_instantiate_and_link() when
 549 * adding a key to a keyring.
 550 *
 551 * This is meant to be stored in a key_restriction structure which is passed
 552 * in the restrict_link parameter to keyring_alloc().
 553 */
 554int restrict_link_reject(struct key *keyring,
 555			 const struct key_type *type,
 556			 const union key_payload *payload,
 557			 struct key *restriction_key)
 558{
 559	return -EPERM;
 560}
 561
 562/*
 563 * By default, we keys found by getting an exact match on their descriptions.
 564 */
 565bool key_default_cmp(const struct key *key,
 566		     const struct key_match_data *match_data)
 567{
 568	return strcmp(key->description, match_data->raw_data) == 0;
 569}
 570
 571/*
 572 * Iteration function to consider each key found.
 573 */
 574static int keyring_search_iterator(const void *object, void *iterator_data)
 575{
 576	struct keyring_search_context *ctx = iterator_data;
 577	const struct key *key = keyring_ptr_to_key(object);
 578	unsigned long kflags = READ_ONCE(key->flags);
 579	short state = READ_ONCE(key->state);
 580
 581	kenter("{%d}", key->serial);
 582
 583	/* ignore keys not of this type */
 584	if (key->type != ctx->index_key.type) {
 585		kleave(" = 0 [!type]");
 586		return 0;
 587	}
 588
 589	/* skip invalidated, revoked and expired keys */
 590	if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
 591		time64_t expiry = READ_ONCE(key->expiry);
 592
 593		if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
 594			      (1 << KEY_FLAG_REVOKED))) {
 595			ctx->result = ERR_PTR(-EKEYREVOKED);
 596			kleave(" = %d [invrev]", ctx->skipped_ret);
 597			goto skipped;
 598		}
 599
 600		if (expiry && ctx->now >= expiry) {
 601			if (!(ctx->flags & KEYRING_SEARCH_SKIP_EXPIRED))
 602				ctx->result = ERR_PTR(-EKEYEXPIRED);
 603			kleave(" = %d [expire]", ctx->skipped_ret);
 604			goto skipped;
 605		}
 606	}
 607
 608	/* keys that don't match */
 609	if (!ctx->match_data.cmp(key, &ctx->match_data)) {
 610		kleave(" = 0 [!match]");
 611		return 0;
 612	}
 613
 614	/* key must have search permissions */
 615	if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
 616	    key_task_permission(make_key_ref(key, ctx->possessed),
 617				ctx->cred, KEY_NEED_SEARCH) < 0) {
 618		ctx->result = ERR_PTR(-EACCES);
 619		kleave(" = %d [!perm]", ctx->skipped_ret);
 620		goto skipped;
 621	}
 622
 623	if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
 624		/* we set a different error code if we pass a negative key */
 625		if (state < 0) {
 626			ctx->result = ERR_PTR(state);
 627			kleave(" = %d [neg]", ctx->skipped_ret);
 628			goto skipped;
 629		}
 630	}
 631
 632	/* Found */
 633	ctx->result = make_key_ref(key, ctx->possessed);
 634	kleave(" = 1 [found]");
 635	return 1;
 636
 637skipped:
 638	return ctx->skipped_ret;
 639}
 640
 641/*
 642 * Search inside a keyring for a key.  We can search by walking to it
 643 * directly based on its index-key or we can iterate over the entire
 644 * tree looking for it, based on the match function.
 645 */
 646static int search_keyring(struct key *keyring, struct keyring_search_context *ctx)
 647{
 648	if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_DIRECT) {
 649		const void *object;
 650
 651		object = assoc_array_find(&keyring->keys,
 652					  &keyring_assoc_array_ops,
 653					  &ctx->index_key);
 654		return object ? ctx->iterator(object, ctx) : 0;
 655	}
 656	return assoc_array_iterate(&keyring->keys, ctx->iterator, ctx);
 657}
 658
 659/*
 660 * Search a tree of keyrings that point to other keyrings up to the maximum
 661 * depth.
 662 */
 663static bool search_nested_keyrings(struct key *keyring,
 664				   struct keyring_search_context *ctx)
 665{
 666	struct {
 667		struct key *keyring;
 668		struct assoc_array_node *node;
 669		int slot;
 670	} stack[KEYRING_SEARCH_MAX_DEPTH];
 671
 672	struct assoc_array_shortcut *shortcut;
 673	struct assoc_array_node *node;
 674	struct assoc_array_ptr *ptr;
 675	struct key *key;
 676	int sp = 0, slot;
 677
 678	kenter("{%d},{%s,%s}",
 679	       keyring->serial,
 680	       ctx->index_key.type->name,
 681	       ctx->index_key.description);
 682
 683#define STATE_CHECKS (KEYRING_SEARCH_NO_STATE_CHECK | KEYRING_SEARCH_DO_STATE_CHECK)
 684	BUG_ON((ctx->flags & STATE_CHECKS) == 0 ||
 685	       (ctx->flags & STATE_CHECKS) == STATE_CHECKS);
 686
 687	if (ctx->index_key.description)
 688		key_set_index_key(&ctx->index_key);
 689
 690	/* Check to see if this top-level keyring is what we are looking for
 691	 * and whether it is valid or not.
 692	 */
 693	if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_ITERATE ||
 694	    keyring_compare_object(keyring, &ctx->index_key)) {
 695		ctx->skipped_ret = 2;
 696		switch (ctx->iterator(keyring_key_to_ptr(keyring), ctx)) {
 697		case 1:
 698			goto found;
 699		case 2:
 700			return false;
 701		default:
 702			break;
 703		}
 704	}
 705
 706	ctx->skipped_ret = 0;
 707
 708	/* Start processing a new keyring */
 709descend_to_keyring:
 710	kdebug("descend to %d", keyring->serial);
 711	if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
 712			      (1 << KEY_FLAG_REVOKED)))
 713		goto not_this_keyring;
 714
 715	/* Search through the keys in this keyring before its searching its
 716	 * subtrees.
 717	 */
 718	if (search_keyring(keyring, ctx))
 719		goto found;
 720
 721	/* Then manually iterate through the keyrings nested in this one.
 722	 *
 723	 * Start from the root node of the index tree.  Because of the way the
 724	 * hash function has been set up, keyrings cluster on the leftmost
 725	 * branch of the root node (root slot 0) or in the root node itself.
 726	 * Non-keyrings avoid the leftmost branch of the root entirely (root
 727	 * slots 1-15).
 728	 */
 729	if (!(ctx->flags & KEYRING_SEARCH_RECURSE))
 730		goto not_this_keyring;
 731
 732	ptr = READ_ONCE(keyring->keys.root);
 733	if (!ptr)
 734		goto not_this_keyring;
 735
 736	if (assoc_array_ptr_is_shortcut(ptr)) {
 737		/* If the root is a shortcut, either the keyring only contains
 738		 * keyring pointers (everything clusters behind root slot 0) or
 739		 * doesn't contain any keyring pointers.
 740		 */
 741		shortcut = assoc_array_ptr_to_shortcut(ptr);
 742		if ((shortcut->index_key[0] & ASSOC_ARRAY_FAN_MASK) != 0)
 743			goto not_this_keyring;
 744
 745		ptr = READ_ONCE(shortcut->next_node);
 746		node = assoc_array_ptr_to_node(ptr);
 747		goto begin_node;
 748	}
 749
 750	node = assoc_array_ptr_to_node(ptr);
 751	ptr = node->slots[0];
 752	if (!assoc_array_ptr_is_meta(ptr))
 753		goto begin_node;
 754
 755descend_to_node:
 756	/* Descend to a more distal node in this keyring's content tree and go
 757	 * through that.
 758	 */
 759	kdebug("descend");
 760	if (assoc_array_ptr_is_shortcut(ptr)) {
 761		shortcut = assoc_array_ptr_to_shortcut(ptr);
 762		ptr = READ_ONCE(shortcut->next_node);
 763		BUG_ON(!assoc_array_ptr_is_node(ptr));
 764	}
 765	node = assoc_array_ptr_to_node(ptr);
 766
 767begin_node:
 768	kdebug("begin_node");
 769	slot = 0;
 770ascend_to_node:
 771	/* Go through the slots in a node */
 772	for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
 773		ptr = READ_ONCE(node->slots[slot]);
 774
 775		if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
 776			goto descend_to_node;
 777
 778		if (!keyring_ptr_is_keyring(ptr))
 779			continue;
 780
 781		key = keyring_ptr_to_key(ptr);
 782
 783		if (sp >= KEYRING_SEARCH_MAX_DEPTH) {
 784			if (ctx->flags & KEYRING_SEARCH_DETECT_TOO_DEEP) {
 785				ctx->result = ERR_PTR(-ELOOP);
 786				return false;
 787			}
 788			goto not_this_keyring;
 789		}
 790
 791		/* Search a nested keyring */
 792		if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
 793		    key_task_permission(make_key_ref(key, ctx->possessed),
 794					ctx->cred, KEY_NEED_SEARCH) < 0)
 795			continue;
 796
 797		/* stack the current position */
 798		stack[sp].keyring = keyring;
 799		stack[sp].node = node;
 800		stack[sp].slot = slot;
 801		sp++;
 802
 803		/* begin again with the new keyring */
 804		keyring = key;
 805		goto descend_to_keyring;
 806	}
 807
 808	/* We've dealt with all the slots in the current node, so now we need
 809	 * to ascend to the parent and continue processing there.
 810	 */
 811	ptr = READ_ONCE(node->back_pointer);
 812	slot = node->parent_slot;
 813
 814	if (ptr && assoc_array_ptr_is_shortcut(ptr)) {
 815		shortcut = assoc_array_ptr_to_shortcut(ptr);
 816		ptr = READ_ONCE(shortcut->back_pointer);
 817		slot = shortcut->parent_slot;
 818	}
 819	if (!ptr)
 820		goto not_this_keyring;
 821	node = assoc_array_ptr_to_node(ptr);
 822	slot++;
 823
 824	/* If we've ascended to the root (zero backpointer), we must have just
 825	 * finished processing the leftmost branch rather than the root slots -
 826	 * so there can't be any more keyrings for us to find.
 827	 */
 828	if (node->back_pointer) {
 829		kdebug("ascend %d", slot);
 830		goto ascend_to_node;
 831	}
 832
 833	/* The keyring we're looking at was disqualified or didn't contain a
 834	 * matching key.
 835	 */
 836not_this_keyring:
 837	kdebug("not_this_keyring %d", sp);
 838	if (sp <= 0) {
 839		kleave(" = false");
 840		return false;
 841	}
 842
 843	/* Resume the processing of a keyring higher up in the tree */
 844	sp--;
 845	keyring = stack[sp].keyring;
 846	node = stack[sp].node;
 847	slot = stack[sp].slot + 1;
 848	kdebug("ascend to %d [%d]", keyring->serial, slot);
 849	goto ascend_to_node;
 850
 851	/* We found a viable match */
 852found:
 853	key = key_ref_to_ptr(ctx->result);
 854	key_check(key);
 855	if (!(ctx->flags & KEYRING_SEARCH_NO_UPDATE_TIME)) {
 856		key->last_used_at = ctx->now;
 857		keyring->last_used_at = ctx->now;
 858		while (sp > 0)
 859			stack[--sp].keyring->last_used_at = ctx->now;
 860	}
 861	kleave(" = true");
 862	return true;
 863}
 864
 865/**
 866 * keyring_search_rcu - Search a keyring tree for a matching key under RCU
 867 * @keyring_ref: A pointer to the keyring with possession indicator.
 868 * @ctx: The keyring search context.
 869 *
 870 * Search the supplied keyring tree for a key that matches the criteria given.
 871 * The root keyring and any linked keyrings must grant Search permission to the
 872 * caller to be searchable and keys can only be found if they too grant Search
 873 * to the caller. The possession flag on the root keyring pointer controls use
 874 * of the possessor bits in permissions checking of the entire tree.  In
 875 * addition, the LSM gets to forbid keyring searches and key matches.
 876 *
 877 * The search is performed as a breadth-then-depth search up to the prescribed
 878 * limit (KEYRING_SEARCH_MAX_DEPTH).  The caller must hold the RCU read lock to
 879 * prevent keyrings from being destroyed or rearranged whilst they are being
 880 * searched.
 881 *
 882 * Keys are matched to the type provided and are then filtered by the match
 883 * function, which is given the description to use in any way it sees fit.  The
 884 * match function may use any attributes of a key that it wishes to to
 885 * determine the match.  Normally the match function from the key type would be
 886 * used.
 887 *
 888 * RCU can be used to prevent the keyring key lists from disappearing without
 889 * the need to take lots of locks.
 890 *
 891 * Returns a pointer to the found key and increments the key usage count if
 892 * successful; -EAGAIN if no matching keys were found, or if expired or revoked
 893 * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
 894 * specified keyring wasn't a keyring.
 895 *
 896 * In the case of a successful return, the possession attribute from
 897 * @keyring_ref is propagated to the returned key reference.
 898 */
 899key_ref_t keyring_search_rcu(key_ref_t keyring_ref,
 900			     struct keyring_search_context *ctx)
 901{
 902	struct key *keyring;
 903	long err;
 904
 905	ctx->iterator = keyring_search_iterator;
 906	ctx->possessed = is_key_possessed(keyring_ref);
 907	ctx->result = ERR_PTR(-EAGAIN);
 908
 909	keyring = key_ref_to_ptr(keyring_ref);
 910	key_check(keyring);
 911
 912	if (keyring->type != &key_type_keyring)
 913		return ERR_PTR(-ENOTDIR);
 914
 915	if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM)) {
 916		err = key_task_permission(keyring_ref, ctx->cred, KEY_NEED_SEARCH);
 917		if (err < 0)
 918			return ERR_PTR(err);
 919	}
 920
 921	ctx->now = ktime_get_real_seconds();
 922	if (search_nested_keyrings(keyring, ctx))
 923		__key_get(key_ref_to_ptr(ctx->result));
 924	return ctx->result;
 925}
 926
 927/**
 928 * keyring_search - Search the supplied keyring tree for a matching key
 929 * @keyring: The root of the keyring tree to be searched.
 930 * @type: The type of keyring we want to find.
 931 * @description: The name of the keyring we want to find.
 932 * @recurse: True to search the children of @keyring also
 933 *
 934 * As keyring_search_rcu() above, but using the current task's credentials and
 935 * type's default matching function and preferred search method.
 936 */
 937key_ref_t keyring_search(key_ref_t keyring,
 938			 struct key_type *type,
 939			 const char *description,
 940			 bool recurse)
 941{
 942	struct keyring_search_context ctx = {
 943		.index_key.type		= type,
 944		.index_key.description	= description,
 945		.index_key.desc_len	= strlen(description),
 946		.cred			= current_cred(),
 947		.match_data.cmp		= key_default_cmp,
 948		.match_data.raw_data	= description,
 949		.match_data.lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
 950		.flags			= KEYRING_SEARCH_DO_STATE_CHECK,
 951	};
 952	key_ref_t key;
 953	int ret;
 954
 955	if (recurse)
 956		ctx.flags |= KEYRING_SEARCH_RECURSE;
 957	if (type->match_preparse) {
 958		ret = type->match_preparse(&ctx.match_data);
 959		if (ret < 0)
 960			return ERR_PTR(ret);
 961	}
 962
 963	rcu_read_lock();
 964	key = keyring_search_rcu(keyring, &ctx);
 965	rcu_read_unlock();
 966
 967	if (type->match_free)
 968		type->match_free(&ctx.match_data);
 969	return key;
 970}
 971EXPORT_SYMBOL(keyring_search);
 972
 973static struct key_restriction *keyring_restriction_alloc(
 974	key_restrict_link_func_t check)
 975{
 976	struct key_restriction *keyres =
 977		kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
 978
 979	if (!keyres)
 980		return ERR_PTR(-ENOMEM);
 981
 982	keyres->check = check;
 983
 984	return keyres;
 985}
 986
 987/*
 988 * Semaphore to serialise restriction setup to prevent reference count
 989 * cycles through restriction key pointers.
 990 */
 991static DECLARE_RWSEM(keyring_serialise_restrict_sem);
 992
 993/*
 994 * Check for restriction cycles that would prevent keyring garbage collection.
 995 * keyring_serialise_restrict_sem must be held.
 996 */
 997static bool keyring_detect_restriction_cycle(const struct key *dest_keyring,
 998					     struct key_restriction *keyres)
 999{
1000	while (keyres && keyres->key &&
1001	       keyres->key->type == &key_type_keyring) {
1002		if (keyres->key == dest_keyring)
1003			return true;
1004
1005		keyres = keyres->key->restrict_link;
1006	}
1007
1008	return false;
1009}
1010
1011/**
1012 * keyring_restrict - Look up and apply a restriction to a keyring
1013 * @keyring_ref: The keyring to be restricted
1014 * @type: The key type that will provide the restriction checker.
1015 * @restriction: The restriction options to apply to the keyring
1016 *
1017 * Look up a keyring and apply a restriction to it.  The restriction is managed
1018 * by the specific key type, but can be configured by the options specified in
1019 * the restriction string.
1020 */
1021int keyring_restrict(key_ref_t keyring_ref, const char *type,
1022		     const char *restriction)
1023{
1024	struct key *keyring;
1025	struct key_type *restrict_type = NULL;
1026	struct key_restriction *restrict_link;
1027	int ret = 0;
1028
1029	keyring = key_ref_to_ptr(keyring_ref);
1030	key_check(keyring);
1031
1032	if (keyring->type != &key_type_keyring)
1033		return -ENOTDIR;
1034
1035	if (!type) {
1036		restrict_link = keyring_restriction_alloc(restrict_link_reject);
1037	} else {
1038		restrict_type = key_type_lookup(type);
1039
1040		if (IS_ERR(restrict_type))
1041			return PTR_ERR(restrict_type);
1042
1043		if (!restrict_type->lookup_restriction) {
1044			ret = -ENOENT;
1045			goto error;
1046		}
1047
1048		restrict_link = restrict_type->lookup_restriction(restriction);
1049	}
1050
1051	if (IS_ERR(restrict_link)) {
1052		ret = PTR_ERR(restrict_link);
1053		goto error;
1054	}
1055
1056	down_write(&keyring->sem);
1057	down_write(&keyring_serialise_restrict_sem);
1058
1059	if (keyring->restrict_link) {
1060		ret = -EEXIST;
1061	} else if (keyring_detect_restriction_cycle(keyring, restrict_link)) {
1062		ret = -EDEADLK;
1063	} else {
1064		keyring->restrict_link = restrict_link;
1065		notify_key(keyring, NOTIFY_KEY_SETATTR, 0);
1066	}
1067
1068	up_write(&keyring_serialise_restrict_sem);
1069	up_write(&keyring->sem);
1070
1071	if (ret < 0) {
1072		key_put(restrict_link->key);
1073		kfree(restrict_link);
1074	}
1075
1076error:
1077	if (restrict_type)
1078		key_type_put(restrict_type);
1079
1080	return ret;
1081}
1082EXPORT_SYMBOL(keyring_restrict);
1083
1084/*
1085 * Search the given keyring for a key that might be updated.
1086 *
1087 * The caller must guarantee that the keyring is a keyring and that the
1088 * permission is granted to modify the keyring as no check is made here.  The
1089 * caller must also hold a lock on the keyring semaphore.
1090 *
1091 * Returns a pointer to the found key with usage count incremented if
1092 * successful and returns NULL if not found.  Revoked and invalidated keys are
1093 * skipped over.
1094 *
1095 * If successful, the possession indicator is propagated from the keyring ref
1096 * to the returned key reference.
1097 */
1098key_ref_t find_key_to_update(key_ref_t keyring_ref,
1099			     const struct keyring_index_key *index_key)
1100{
1101	struct key *keyring, *key;
1102	const void *object;
1103
1104	keyring = key_ref_to_ptr(keyring_ref);
1105
1106	kenter("{%d},{%s,%s}",
1107	       keyring->serial, index_key->type->name, index_key->description);
1108
1109	object = assoc_array_find(&keyring->keys, &keyring_assoc_array_ops,
1110				  index_key);
1111
1112	if (object)
1113		goto found;
1114
1115	kleave(" = NULL");
1116	return NULL;
1117
1118found:
1119	key = keyring_ptr_to_key(object);
1120	if (key->flags & ((1 << KEY_FLAG_INVALIDATED) |
1121			  (1 << KEY_FLAG_REVOKED))) {
1122		kleave(" = NULL [x]");
1123		return NULL;
1124	}
1125	__key_get(key);
1126	kleave(" = {%d}", key->serial);
1127	return make_key_ref(key, is_key_possessed(keyring_ref));
1128}
1129
1130/*
1131 * Find a keyring with the specified name.
1132 *
1133 * Only keyrings that have nonzero refcount, are not revoked, and are owned by a
1134 * user in the current user namespace are considered.  If @uid_keyring is %true,
1135 * the keyring additionally must have been allocated as a user or user session
1136 * keyring; otherwise, it must grant Search permission directly to the caller.
1137 *
1138 * Returns a pointer to the keyring with the keyring's refcount having being
1139 * incremented on success.  -ENOKEY is returned if a key could not be found.
1140 */
1141struct key *find_keyring_by_name(const char *name, bool uid_keyring)
1142{
1143	struct user_namespace *ns = current_user_ns();
1144	struct key *keyring;
1145
1146	if (!name)
1147		return ERR_PTR(-EINVAL);
1148
1149	read_lock(&keyring_name_lock);
1150
1151	/* Search this hash bucket for a keyring with a matching name that
1152	 * grants Search permission and that hasn't been revoked
1153	 */
1154	list_for_each_entry(keyring, &ns->keyring_name_list, name_link) {
1155		if (!kuid_has_mapping(ns, keyring->user->uid))
1156			continue;
1157
1158		if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
1159			continue;
1160
1161		if (strcmp(keyring->description, name) != 0)
1162			continue;
1163
1164		if (uid_keyring) {
1165			if (!test_bit(KEY_FLAG_UID_KEYRING,
1166				      &keyring->flags))
1167				continue;
1168		} else {
1169			if (key_permission(make_key_ref(keyring, 0),
1170					   KEY_NEED_SEARCH) < 0)
1171				continue;
1172		}
1173
1174		/* we've got a match but we might end up racing with
1175		 * key_cleanup() if the keyring is currently 'dead'
1176		 * (ie. it has a zero usage count) */
1177		if (!refcount_inc_not_zero(&keyring->usage))
1178			continue;
1179		keyring->last_used_at = ktime_get_real_seconds();
1180		goto out;
1181	}
1182
1183	keyring = ERR_PTR(-ENOKEY);
1184out:
1185	read_unlock(&keyring_name_lock);
1186	return keyring;
1187}
1188
1189static int keyring_detect_cycle_iterator(const void *object,
1190					 void *iterator_data)
1191{
1192	struct keyring_search_context *ctx = iterator_data;
1193	const struct key *key = keyring_ptr_to_key(object);
1194
1195	kenter("{%d}", key->serial);
1196
1197	/* We might get a keyring with matching index-key that is nonetheless a
1198	 * different keyring. */
1199	if (key != ctx->match_data.raw_data)
1200		return 0;
1201
1202	ctx->result = ERR_PTR(-EDEADLK);
1203	return 1;
1204}
1205
1206/*
1207 * See if a cycle will will be created by inserting acyclic tree B in acyclic
1208 * tree A at the topmost level (ie: as a direct child of A).
1209 *
1210 * Since we are adding B to A at the top level, checking for cycles should just
1211 * be a matter of seeing if node A is somewhere in tree B.
1212 */
1213static int keyring_detect_cycle(struct key *A, struct key *B)
1214{
1215	struct keyring_search_context ctx = {
1216		.index_key		= A->index_key,
1217		.match_data.raw_data	= A,
1218		.match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
1219		.iterator		= keyring_detect_cycle_iterator,
1220		.flags			= (KEYRING_SEARCH_NO_STATE_CHECK |
1221					   KEYRING_SEARCH_NO_UPDATE_TIME |
1222					   KEYRING_SEARCH_NO_CHECK_PERM |
1223					   KEYRING_SEARCH_DETECT_TOO_DEEP |
1224					   KEYRING_SEARCH_RECURSE),
1225	};
1226
1227	rcu_read_lock();
1228	search_nested_keyrings(B, &ctx);
1229	rcu_read_unlock();
1230	return PTR_ERR(ctx.result) == -EAGAIN ? 0 : PTR_ERR(ctx.result);
1231}
1232
1233/*
1234 * Lock keyring for link.
1235 */
1236int __key_link_lock(struct key *keyring,
1237		    const struct keyring_index_key *index_key)
1238	__acquires(&keyring->sem)
1239	__acquires(&keyring_serialise_link_lock)
1240{
1241	if (keyring->type != &key_type_keyring)
1242		return -ENOTDIR;
1243
1244	down_write(&keyring->sem);
1245
1246	/* Serialise link/link calls to prevent parallel calls causing a cycle
1247	 * when linking two keyring in opposite orders.
1248	 */
1249	if (index_key->type == &key_type_keyring)
1250		mutex_lock(&keyring_serialise_link_lock);
1251
1252	return 0;
1253}
1254
1255/*
1256 * Lock keyrings for move (link/unlink combination).
1257 */
1258int __key_move_lock(struct key *l_keyring, struct key *u_keyring,
1259		    const struct keyring_index_key *index_key)
1260	__acquires(&l_keyring->sem)
1261	__acquires(&u_keyring->sem)
1262	__acquires(&keyring_serialise_link_lock)
1263{
1264	if (l_keyring->type != &key_type_keyring ||
1265	    u_keyring->type != &key_type_keyring)
1266		return -ENOTDIR;
1267
1268	/* We have to be very careful here to take the keyring locks in the
1269	 * right order, lest we open ourselves to deadlocking against another
1270	 * move operation.
1271	 */
1272	if (l_keyring < u_keyring) {
1273		down_write(&l_keyring->sem);
1274		down_write_nested(&u_keyring->sem, 1);
1275	} else {
1276		down_write(&u_keyring->sem);
1277		down_write_nested(&l_keyring->sem, 1);
1278	}
1279
1280	/* Serialise link/link calls to prevent parallel calls causing a cycle
1281	 * when linking two keyring in opposite orders.
1282	 */
1283	if (index_key->type == &key_type_keyring)
1284		mutex_lock(&keyring_serialise_link_lock);
1285
1286	return 0;
1287}
1288
1289/*
1290 * Preallocate memory so that a key can be linked into to a keyring.
1291 */
1292int __key_link_begin(struct key *keyring,
1293		     const struct keyring_index_key *index_key,
1294		     struct assoc_array_edit **_edit)
1295{
1296	struct assoc_array_edit *edit;
1297	int ret;
1298
1299	kenter("%d,%s,%s,",
1300	       keyring->serial, index_key->type->name, index_key->description);
1301
1302	BUG_ON(index_key->desc_len == 0);
1303	BUG_ON(*_edit != NULL);
1304
1305	*_edit = NULL;
1306
1307	ret = -EKEYREVOKED;
1308	if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
1309		goto error;
1310
1311	/* Create an edit script that will insert/replace the key in the
1312	 * keyring tree.
1313	 */
1314	edit = assoc_array_insert(&keyring->keys,
1315				  &keyring_assoc_array_ops,
1316				  index_key,
1317				  NULL);
1318	if (IS_ERR(edit)) {
1319		ret = PTR_ERR(edit);
1320		goto error;
1321	}
1322
1323	/* If we're not replacing a link in-place then we're going to need some
1324	 * extra quota.
1325	 */
1326	if (!edit->dead_leaf) {
1327		ret = key_payload_reserve(keyring,
1328					  keyring->datalen + KEYQUOTA_LINK_BYTES);
1329		if (ret < 0)
1330			goto error_cancel;
1331	}
1332
1333	*_edit = edit;
1334	kleave(" = 0");
1335	return 0;
1336
1337error_cancel:
1338	assoc_array_cancel_edit(edit);
1339error:
1340	kleave(" = %d", ret);
1341	return ret;
1342}
1343
1344/*
1345 * Check already instantiated keys aren't going to be a problem.
1346 *
1347 * The caller must have called __key_link_begin(). Don't need to call this for
1348 * keys that were created since __key_link_begin() was called.
1349 */
1350int __key_link_check_live_key(struct key *keyring, struct key *key)
1351{
1352	if (key->type == &key_type_keyring)
1353		/* check that we aren't going to create a cycle by linking one
1354		 * keyring to another */
1355		return keyring_detect_cycle(keyring, key);
1356	return 0;
1357}
1358
1359/*
1360 * Link a key into to a keyring.
1361 *
1362 * Must be called with __key_link_begin() having being called.  Discards any
1363 * already extant link to matching key if there is one, so that each keyring
1364 * holds at most one link to any given key of a particular type+description
1365 * combination.
1366 */
1367void __key_link(struct key *keyring, struct key *key,
1368		struct assoc_array_edit **_edit)
1369{
1370	__key_get(key);
1371	assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key));
1372	assoc_array_apply_edit(*_edit);
1373	*_edit = NULL;
1374	notify_key(keyring, NOTIFY_KEY_LINKED, key_serial(key));
1375}
1376
1377/*
1378 * Finish linking a key into to a keyring.
1379 *
1380 * Must be called with __key_link_begin() having being called.
1381 */
1382void __key_link_end(struct key *keyring,
1383		    const struct keyring_index_key *index_key,
1384		    struct assoc_array_edit *edit)
1385	__releases(&keyring->sem)
1386	__releases(&keyring_serialise_link_lock)
1387{
1388	BUG_ON(index_key->type == NULL);
1389	kenter("%d,%s,", keyring->serial, index_key->type->name);
1390
1391	if (edit) {
1392		if (!edit->dead_leaf) {
1393			key_payload_reserve(keyring,
1394				keyring->datalen - KEYQUOTA_LINK_BYTES);
1395		}
1396		assoc_array_cancel_edit(edit);
1397	}
1398	up_write(&keyring->sem);
1399
1400	if (index_key->type == &key_type_keyring)
1401		mutex_unlock(&keyring_serialise_link_lock);
1402}
1403
1404/*
1405 * Check addition of keys to restricted keyrings.
1406 */
1407static int __key_link_check_restriction(struct key *keyring, struct key *key)
1408{
1409	if (!keyring->restrict_link || !keyring->restrict_link->check)
1410		return 0;
1411	return keyring->restrict_link->check(keyring, key->type, &key->payload,
1412					     keyring->restrict_link->key);
1413}
1414
1415/**
1416 * key_link - Link a key to a keyring
1417 * @keyring: The keyring to make the link in.
1418 * @key: The key to link to.
1419 *
1420 * Make a link in a keyring to a key, such that the keyring holds a reference
1421 * on that key and the key can potentially be found by searching that keyring.
1422 *
1423 * This function will write-lock the keyring's semaphore and will consume some
1424 * of the user's key data quota to hold the link.
1425 *
1426 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
1427 * -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
1428 * full, -EDQUOT if there is insufficient key data quota remaining to add
1429 * another link or -ENOMEM if there's insufficient memory.
1430 *
1431 * It is assumed that the caller has checked that it is permitted for a link to
1432 * be made (the keyring should have Write permission and the key Link
1433 * permission).
1434 */
1435int key_link(struct key *keyring, struct key *key)
1436{
1437	struct assoc_array_edit *edit = NULL;
1438	int ret;
1439
1440	kenter("{%d,%d}", keyring->serial, refcount_read(&keyring->usage));
1441
1442	key_check(keyring);
1443	key_check(key);
1444
1445	ret = __key_link_lock(keyring, &key->index_key);
1446	if (ret < 0)
1447		goto error;
1448
1449	ret = __key_link_begin(keyring, &key->index_key, &edit);
1450	if (ret < 0)
1451		goto error_end;
1452
1453	kdebug("begun {%d,%d}", keyring->serial, refcount_read(&keyring->usage));
1454	ret = __key_link_check_restriction(keyring, key);
1455	if (ret == 0)
1456		ret = __key_link_check_live_key(keyring, key);
1457	if (ret == 0)
1458		__key_link(keyring, key, &edit);
1459
1460error_end:
1461	__key_link_end(keyring, &key->index_key, edit);
1462error:
1463	kleave(" = %d {%d,%d}", ret, keyring->serial, refcount_read(&keyring->usage));
1464	return ret;
1465}
1466EXPORT_SYMBOL(key_link);
1467
1468/*
1469 * Lock a keyring for unlink.
1470 */
1471static int __key_unlink_lock(struct key *keyring)
1472	__acquires(&keyring->sem)
1473{
1474	if (keyring->type != &key_type_keyring)
1475		return -ENOTDIR;
1476
1477	down_write(&keyring->sem);
1478	return 0;
1479}
1480
1481/*
1482 * Begin the process of unlinking a key from a keyring.
1483 */
1484static int __key_unlink_begin(struct key *keyring, struct key *key,
1485			      struct assoc_array_edit **_edit)
1486{
1487	struct assoc_array_edit *edit;
1488
1489	BUG_ON(*_edit != NULL);
1490
1491	edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops,
1492				  &key->index_key);
1493	if (IS_ERR(edit))
1494		return PTR_ERR(edit);
1495
1496	if (!edit)
1497		return -ENOENT;
1498
1499	*_edit = edit;
1500	return 0;
1501}
1502
1503/*
1504 * Apply an unlink change.
1505 */
1506static void __key_unlink(struct key *keyring, struct key *key,
1507			 struct assoc_array_edit **_edit)
1508{
1509	assoc_array_apply_edit(*_edit);
1510	notify_key(keyring, NOTIFY_KEY_UNLINKED, key_serial(key));
1511	*_edit = NULL;
1512	key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES);
1513}
1514
1515/*
1516 * Finish unlinking a key from to a keyring.
1517 */
1518static void __key_unlink_end(struct key *keyring,
1519			     struct key *key,
1520			     struct assoc_array_edit *edit)
1521	__releases(&keyring->sem)
1522{
1523	if (edit)
1524		assoc_array_cancel_edit(edit);
1525	up_write(&keyring->sem);
1526}
1527
1528/**
1529 * key_unlink - Unlink the first link to a key from a keyring.
1530 * @keyring: The keyring to remove the link from.
1531 * @key: The key the link is to.
1532 *
1533 * Remove a link from a keyring to a key.
1534 *
1535 * This function will write-lock the keyring's semaphore.
1536 *
1537 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
1538 * the key isn't linked to by the keyring or -ENOMEM if there's insufficient
1539 * memory.
1540 *
1541 * It is assumed that the caller has checked that it is permitted for a link to
1542 * be removed (the keyring should have Write permission; no permissions are
1543 * required on the key).
1544 */
1545int key_unlink(struct key *keyring, struct key *key)
1546{
1547	struct assoc_array_edit *edit = NULL;
1548	int ret;
1549
1550	key_check(keyring);
1551	key_check(key);
1552
1553	ret = __key_unlink_lock(keyring);
1554	if (ret < 0)
1555		return ret;
1556
1557	ret = __key_unlink_begin(keyring, key, &edit);
1558	if (ret == 0)
1559		__key_unlink(keyring, key, &edit);
1560	__key_unlink_end(keyring, key, edit);
1561	return ret;
1562}
1563EXPORT_SYMBOL(key_unlink);
1564
1565/**
1566 * key_move - Move a key from one keyring to another
1567 * @key: The key to move
1568 * @from_keyring: The keyring to remove the link from.
1569 * @to_keyring: The keyring to make the link in.
1570 * @flags: Qualifying flags, such as KEYCTL_MOVE_EXCL.
1571 *
1572 * Make a link in @to_keyring to a key, such that the keyring holds a reference
1573 * on that key and the key can potentially be found by searching that keyring
1574 * whilst simultaneously removing a link to the key from @from_keyring.
1575 *
1576 * This function will write-lock both keyring's semaphores and will consume
1577 * some of the user's key data quota to hold the link on @to_keyring.
1578 *
1579 * Returns 0 if successful, -ENOTDIR if either keyring isn't a keyring,
1580 * -EKEYREVOKED if either keyring has been revoked, -ENFILE if the second
1581 * keyring is full, -EDQUOT if there is insufficient key data quota remaining
1582 * to add another link or -ENOMEM if there's insufficient memory.  If
1583 * KEYCTL_MOVE_EXCL is set, then -EEXIST will be returned if there's already a
1584 * matching key in @to_keyring.
1585 *
1586 * It is assumed that the caller has checked that it is permitted for a link to
1587 * be made (the keyring should have Write permission and the key Link
1588 * permission).
1589 */
1590int key_move(struct key *key,
1591	     struct key *from_keyring,
1592	     struct key *to_keyring,
1593	     unsigned int flags)
1594{
1595	struct assoc_array_edit *from_edit = NULL, *to_edit = NULL;
1596	int ret;
1597
1598	kenter("%d,%d,%d", key->serial, from_keyring->serial, to_keyring->serial);
1599
1600	if (from_keyring == to_keyring)
1601		return 0;
1602
1603	key_check(key);
1604	key_check(from_keyring);
1605	key_check(to_keyring);
1606
1607	ret = __key_move_lock(from_keyring, to_keyring, &key->index_key);
1608	if (ret < 0)
1609		goto out;
1610	ret = __key_unlink_begin(from_keyring, key, &from_edit);
1611	if (ret < 0)
1612		goto error;
1613	ret = __key_link_begin(to_keyring, &key->index_key, &to_edit);
1614	if (ret < 0)
1615		goto error;
1616
1617	ret = -EEXIST;
1618	if (to_edit->dead_leaf && (flags & KEYCTL_MOVE_EXCL))
1619		goto error;
1620
1621	ret = __key_link_check_restriction(to_keyring, key);
1622	if (ret < 0)
1623		goto error;
1624	ret = __key_link_check_live_key(to_keyring, key);
1625	if (ret < 0)
1626		goto error;
1627
1628	__key_unlink(from_keyring, key, &from_edit);
1629	__key_link(to_keyring, key, &to_edit);
1630error:
1631	__key_link_end(to_keyring, &key->index_key, to_edit);
1632	__key_unlink_end(from_keyring, key, from_edit);
1633out:
1634	kleave(" = %d", ret);
1635	return ret;
1636}
1637EXPORT_SYMBOL(key_move);
1638
1639/**
1640 * keyring_clear - Clear a keyring
1641 * @keyring: The keyring to clear.
1642 *
1643 * Clear the contents of the specified keyring.
1644 *
1645 * Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
1646 */
1647int keyring_clear(struct key *keyring)
1648{
1649	struct assoc_array_edit *edit;
1650	int ret;
1651
1652	if (keyring->type != &key_type_keyring)
1653		return -ENOTDIR;
1654
1655	down_write(&keyring->sem);
1656
1657	edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
1658	if (IS_ERR(edit)) {
1659		ret = PTR_ERR(edit);
1660	} else {
1661		if (edit)
1662			assoc_array_apply_edit(edit);
1663		notify_key(keyring, NOTIFY_KEY_CLEARED, 0);
1664		key_payload_reserve(keyring, 0);
1665		ret = 0;
1666	}
1667
1668	up_write(&keyring->sem);
1669	return ret;
1670}
1671EXPORT_SYMBOL(keyring_clear);
1672
1673/*
1674 * Dispose of the links from a revoked keyring.
1675 *
1676 * This is called with the key sem write-locked.
1677 */
1678static void keyring_revoke(struct key *keyring)
1679{
1680	struct assoc_array_edit *edit;
1681
1682	edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
1683	if (!IS_ERR(edit)) {
1684		if (edit)
1685			assoc_array_apply_edit(edit);
1686		key_payload_reserve(keyring, 0);
1687	}
1688}
1689
1690static bool keyring_gc_select_iterator(void *object, void *iterator_data)
1691{
1692	struct key *key = keyring_ptr_to_key(object);
1693	time64_t *limit = iterator_data;
1694
1695	if (key_is_dead(key, *limit))
1696		return false;
1697	key_get(key);
1698	return true;
1699}
1700
1701static int keyring_gc_check_iterator(const void *object, void *iterator_data)
1702{
1703	const struct key *key = keyring_ptr_to_key(object);
1704	time64_t *limit = iterator_data;
1705
1706	key_check(key);
1707	return key_is_dead(key, *limit);
1708}
1709
1710/*
1711 * Garbage collect pointers from a keyring.
1712 *
1713 * Not called with any locks held.  The keyring's key struct will not be
1714 * deallocated under us as only our caller may deallocate it.
1715 */
1716void keyring_gc(struct key *keyring, time64_t limit)
1717{
1718	int result;
1719
1720	kenter("%x{%s}", keyring->serial, keyring->description ?: "");
1721
1722	if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
1723			      (1 << KEY_FLAG_REVOKED)))
1724		goto dont_gc;
1725
1726	/* scan the keyring looking for dead keys */
1727	rcu_read_lock();
1728	result = assoc_array_iterate(&keyring->keys,
1729				     keyring_gc_check_iterator, &limit);
1730	rcu_read_unlock();
1731	if (result == true)
1732		goto do_gc;
1733
1734dont_gc:
1735	kleave(" [no gc]");
1736	return;
1737
1738do_gc:
1739	down_write(&keyring->sem);
1740	assoc_array_gc(&keyring->keys, &keyring_assoc_array_ops,
1741		       keyring_gc_select_iterator, &limit);
1742	up_write(&keyring->sem);
1743	kleave(" [gc]");
1744}
1745
1746/*
1747 * Garbage collect restriction pointers from a keyring.
1748 *
1749 * Keyring restrictions are associated with a key type, and must be cleaned
1750 * up if the key type is unregistered. The restriction is altered to always
1751 * reject additional keys so a keyring cannot be opened up by unregistering
1752 * a key type.
1753 *
1754 * Not called with any keyring locks held. The keyring's key struct will not
1755 * be deallocated under us as only our caller may deallocate it.
1756 *
1757 * The caller is required to hold key_types_sem and dead_type->sem. This is
1758 * fulfilled by key_gc_keytype() holding the locks on behalf of
1759 * key_garbage_collector(), which it invokes on a workqueue.
1760 */
1761void keyring_restriction_gc(struct key *keyring, struct key_type *dead_type)
1762{
1763	struct key_restriction *keyres;
1764
1765	kenter("%x{%s}", keyring->serial, keyring->description ?: "");
1766
1767	/*
1768	 * keyring->restrict_link is only assigned at key allocation time
1769	 * or with the key type locked, so the only values that could be
1770	 * concurrently assigned to keyring->restrict_link are for key
1771	 * types other than dead_type. Given this, it's ok to check
1772	 * the key type before acquiring keyring->sem.
1773	 */
1774	if (!dead_type || !keyring->restrict_link ||
1775	    keyring->restrict_link->keytype != dead_type) {
1776		kleave(" [no restriction gc]");
1777		return;
1778	}
1779
1780	/* Lock the keyring to ensure that a link is not in progress */
1781	down_write(&keyring->sem);
1782
1783	keyres = keyring->restrict_link;
1784
1785	keyres->check = restrict_link_reject;
1786
1787	key_put(keyres->key);
1788	keyres->key = NULL;
1789	keyres->keytype = NULL;
1790
1791	up_write(&keyring->sem);
1792
1793	kleave(" [restriction gc]");
1794}