text: /* Keyring handling
   *
   * Copyright (C) 2004-2005, 2008, 2013 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/security.h>
  #include <linux/seq_file.h>
  #include <linux/err.h>
  #include <keys/keyring-type.h>
  #include <keys/user-type.h>
  #include <linux/assoc_array_priv.h>
  #include <linux/uaccess.h>
  #include "internal.h"
  
  /*
   * When plumbing the depths of the key tree, this sets a hard limit
   * set on how deep we're willing to go.
   */
  #define KEYRING_SEARCH_MAX_DEPTH 6
  
  /*
   * We keep all named keyrings in a hash to speed looking them up.
   */
  #define KEYRING_NAME_HASH_SIZE	(1 << 5)
  
  /*
   * We mark pointers we pass to the associative array with bit 1 set if
   * they're keyrings and clear otherwise.
   */
  #define KEYRING_PTR_SUBTYPE	0x2UL
  
  static inline bool keyring_ptr_is_keyring(const struct assoc_array_ptr *x)
  {
  	return (unsigned long)x & KEYRING_PTR_SUBTYPE;
  }
  static inline struct key *keyring_ptr_to_key(const struct assoc_array_ptr *x)
  {
  	void *object = assoc_array_ptr_to_leaf(x);
  	return (struct key *)((unsigned long)object & ~KEYRING_PTR_SUBTYPE);
  }
  static inline void *keyring_key_to_ptr(struct key *key)
  {
  	if (key->type == &key_type_keyring)
  		return (void *)((unsigned long)key | KEYRING_PTR_SUBTYPE);
  	return key;
  }
  
  static struct list_head	keyring_name_hash[KEYRING_NAME_HASH_SIZE];
  static DEFINE_RWLOCK(keyring_name_lock);
  
  static inline unsigned keyring_hash(const char *desc)
  {
  	unsigned bucket = 0;
  
  	for (; *desc; desc++)
  		bucket += (unsigned char)*desc;
  
  	return bucket & (KEYRING_NAME_HASH_SIZE - 1);
  }
  
  /*
   * The keyring key type definition.  Keyrings are simply keys of this type and
   * can be treated as ordinary keys in addition to having their own special
   * operations.
   */
  static int keyring_preparse(struct key_preparsed_payload *prep);
  static void keyring_free_preparse(struct key_preparsed_payload *prep);
  static int keyring_instantiate(struct key *keyring,
  			       struct key_preparsed_payload *prep);
  static void keyring_revoke(struct key *keyring);
  static void keyring_destroy(struct key *keyring);
  static void keyring_describe(const struct key *keyring, struct seq_file *m);
  static long keyring_read(const struct key *keyring,
  			 char __user *buffer, size_t buflen);
  
  struct key_type key_type_keyring = {
  	.name		= "keyring",
  	.def_datalen	= 0,
  	.preparse	= keyring_preparse,
  	.free_preparse	= keyring_free_preparse,
  	.instantiate	= keyring_instantiate,
  	.revoke		= keyring_revoke,
  	.destroy	= keyring_destroy,
  	.describe	= keyring_describe,
  	.read		= keyring_read,
  };
  EXPORT_SYMBOL(key_type_keyring);
  
  /*
   * Semaphore to serialise link/link calls to prevent two link calls in parallel
   * introducing a cycle.
   */
  static DECLARE_RWSEM(keyring_serialise_link_sem);
  
  /*
   * Publish the name of a keyring so that it can be found by name (if it has
   * one).
   */
  static void keyring_publish_name(struct key *keyring)
  {
  	int bucket;
  
  	if (keyring->description) {
  		bucket = keyring_hash(keyring->description);
  
  		write_lock(&keyring_name_lock);
  
  		if (!keyring_name_hash[bucket].next)
  			INIT_LIST_HEAD(&keyring_name_hash[bucket]);
  
  		list_add_tail(&keyring->name_link,
  			      &keyring_name_hash[bucket]);
  
  		write_unlock(&keyring_name_lock);
  	}
  }
  
  /*
   * Preparse a keyring payload
   */
  static int keyring_preparse(struct key_preparsed_payload *prep)
  {
  	return prep->datalen != 0 ? -EINVAL : 0;
  }
  
  /*
   * Free a preparse of a user defined key payload
   */
  static void keyring_free_preparse(struct key_preparsed_payload *prep)
  {
  }
  
  /*
   * Initialise a keyring.
   *
   * Returns 0 on success, -EINVAL if given any data.
   */
  static int keyring_instantiate(struct key *keyring,
  			       struct key_preparsed_payload *prep)
  {
  	assoc_array_init(&keyring->keys);
  	/* make the keyring available by name if it has one */
  	keyring_publish_name(keyring);
  	return 0;
  }
  
  /*
   * Multiply 64-bits by 32-bits to 96-bits and fold back to 64-bit.  Ideally we'd
   * fold the carry back too, but that requires inline asm.
   */
  static u64 mult_64x32_and_fold(u64 x, u32 y)
  {
  	u64 hi = (u64)(u32)(x >> 32) * y;
  	u64 lo = (u64)(u32)(x) * y;
  	return lo + ((u64)(u32)hi << 32) + (u32)(hi >> 32);
  }
  
  /*
   * Hash a key type and description.
   */
  static unsigned long hash_key_type_and_desc(const struct keyring_index_key *index_key)
  {
  	const unsigned level_shift = ASSOC_ARRAY_LEVEL_STEP;
  	const unsigned long fan_mask = ASSOC_ARRAY_FAN_MASK;
  	const char *description = index_key->description;
  	unsigned long hash, type;
  	u32 piece;
  	u64 acc;
  	int n, desc_len = index_key->desc_len;
  
  	type = (unsigned long)index_key->type;
  
  	acc = mult_64x32_and_fold(type, desc_len + 13);
  	acc = mult_64x32_and_fold(acc, 9207);
  	for (;;) {
  		n = desc_len;
  		if (n <= 0)
  			break;
  		if (n > 4)
  			n = 4;
  		piece = 0;
  		memcpy(&piece, description, n);
  		description += n;
  		desc_len -= n;
  		acc = mult_64x32_and_fold(acc, piece);
  		acc = mult_64x32_and_fold(acc, 9207);
  	}
  
  	/* Fold the hash down to 32 bits if need be. */
  	hash = acc;
  	if (ASSOC_ARRAY_KEY_CHUNK_SIZE == 32)
  		hash ^= acc >> 32;
  
  	/* Squidge all the keyrings into a separate part of the tree to
  	 * ordinary keys by making sure the lowest level segment in the hash is
  	 * zero for keyrings and non-zero otherwise.
  	 */
  	if (index_key->type != &key_type_keyring && (hash & fan_mask) == 0)
  		return hash | (hash >> (ASSOC_ARRAY_KEY_CHUNK_SIZE - level_shift)) | 1;
  	if (index_key->type == &key_type_keyring && (hash & fan_mask) != 0)
  		return (hash + (hash << level_shift)) & ~fan_mask;
  	return hash;
  }
  
  /*
   * Build the next index key chunk.
   *
   * On 32-bit systems the index key is laid out as:
   *
   *	0	4	5	9...
   *	hash	desclen	typeptr	desc[]
   *
   * On 64-bit systems:
   *
   *	0	8	9	17...
   *	hash	desclen	typeptr	desc[]
   *
   * We return it one word-sized chunk at a time.
   */
  static unsigned long keyring_get_key_chunk(const void *data, int level)
  {
  	const struct keyring_index_key *index_key = data;
  	unsigned long chunk = 0;
  	long offset = 0;
  	int desc_len = index_key->desc_len, n = sizeof(chunk);
  
  	level /= ASSOC_ARRAY_KEY_CHUNK_SIZE;
  	switch (level) {
  	case 0:
  		return hash_key_type_and_desc(index_key);
  	case 1:
  		return ((unsigned long)index_key->type << 8) | desc_len;
  	case 2:
  		if (desc_len == 0)
  			return (u8)((unsigned long)index_key->type >>
  				    (ASSOC_ARRAY_KEY_CHUNK_SIZE - 8));
  		n--;
  		offset = 1;
  	default:
  		offset += sizeof(chunk) - 1;
  		offset += (level - 3) * sizeof(chunk);
  		if (offset >= desc_len)
  			return 0;
  		desc_len -= offset;
  		if (desc_len > n)
  			desc_len = n;
  		offset += desc_len;
  		do {
  			chunk <<= 8;
  			chunk |= ((u8*)index_key->description)[--offset];
  		} while (--desc_len > 0);
  
  		if (level == 2) {
  			chunk <<= 8;
  			chunk |= (u8)((unsigned long)index_key->type >>
  				      (ASSOC_ARRAY_KEY_CHUNK_SIZE - 8));
  		}
  		return chunk;
  	}
  }
  
  static unsigned long keyring_get_object_key_chunk(const void *object, int level)
  {
  	const struct key *key = keyring_ptr_to_key(object);
  	return keyring_get_key_chunk(&key->index_key, level);
  }
  
  static bool keyring_compare_object(const void *object, const void *data)
  {
  	const struct keyring_index_key *index_key = data;
  	const struct key *key = keyring_ptr_to_key(object);
  
  	return key->index_key.type == index_key->type &&
  		key->index_key.desc_len == index_key->desc_len &&
  		memcmp(key->index_key.description, index_key->description,
  		       index_key->desc_len) == 0;
  }
  
  /*
   * Compare the index keys of a pair of objects and determine the bit position
   * at which they differ - if they differ.
   */
  static int keyring_diff_objects(const void *object, const void *data)
  {
  	const struct key *key_a = keyring_ptr_to_key(object);
  	const struct keyring_index_key *a = &key_a->index_key;
  	const struct keyring_index_key *b = data;
  	unsigned long seg_a, seg_b;
  	int level, i;
  
  	level = 0;
  	seg_a = hash_key_type_and_desc(a);
  	seg_b = hash_key_type_and_desc(b);
  	if ((seg_a ^ seg_b) != 0)
  		goto differ;
  
  	/* The number of bits contributed by the hash is controlled by a
  	 * constant in the assoc_array headers.  Everything else thereafter we
  	 * can deal with as being machine word-size dependent.
  	 */
  	level += ASSOC_ARRAY_KEY_CHUNK_SIZE / 8;
  	seg_a = a->desc_len;
  	seg_b = b->desc_len;
  	if ((seg_a ^ seg_b) != 0)
  		goto differ;
  
  	/* The next bit may not work on big endian */
  	level++;
  	seg_a = (unsigned long)a->type;
  	seg_b = (unsigned long)b->type;
  	if ((seg_a ^ seg_b) != 0)
  		goto differ;
  
  	level += sizeof(unsigned long);
  	if (a->desc_len == 0)
  		goto same;
  
  	i = 0;
  	if (((unsigned long)a->description | (unsigned long)b->description) &
  	    (sizeof(unsigned long) - 1)) {
  		do {
  			seg_a = *(unsigned long *)(a->description + i);
  			seg_b = *(unsigned long *)(b->description + i);
  			if ((seg_a ^ seg_b) != 0)
  				goto differ_plus_i;
  			i += sizeof(unsigned long);
  		} while (i < (a->desc_len & (sizeof(unsigned long) - 1)));
  	}
  
  	for (; i < a->desc_len; i++) {
  		seg_a = *(unsigned char *)(a->description + i);
  		seg_b = *(unsigned char *)(b->description + i);
  		if ((seg_a ^ seg_b) != 0)
  			goto differ_plus_i;
  	}
  
  same:
  	return -1;
  
  differ_plus_i:
  	level += i;
  differ:
  	i = level * 8 + __ffs(seg_a ^ seg_b);
  	return i;
  }
  
  /*
   * Free an object after stripping the keyring flag off of the pointer.
   */
  static void keyring_free_object(void *object)
  {
  	key_put(keyring_ptr_to_key(object));
  }
  
  /*
   * Operations for keyring management by the index-tree routines.
   */
  static const struct assoc_array_ops keyring_assoc_array_ops = {
  	.get_key_chunk		= keyring_get_key_chunk,
  	.get_object_key_chunk	= keyring_get_object_key_chunk,
  	.compare_object		= keyring_compare_object,
  	.diff_objects		= keyring_diff_objects,
  	.free_object		= keyring_free_object,
  };
  
  /*
   * Clean up a keyring when it is destroyed.  Unpublish its name if it had one
   * and dispose of its data.
   *
   * The garbage collector detects the final key_put(), removes the keyring from
   * the serial number tree and then does RCU synchronisation before coming here,
   * so we shouldn't need to worry about code poking around here with the RCU
   * readlock held by this time.
   */
  static void keyring_destroy(struct key *keyring)
  {
  	if (keyring->description) {
  		write_lock(&keyring_name_lock);
  
  		if (keyring->name_link.next != NULL &&
  		    !list_empty(&keyring->name_link))
  			list_del(&keyring->name_link);
  
  		write_unlock(&keyring_name_lock);
  	}
  
  	if (keyring->restrict_link) {
  		struct key_restriction *keyres = keyring->restrict_link;
  
  		key_put(keyres->key);
  		kfree(keyres);
  	}
  
  	assoc_array_destroy(&keyring->keys, &keyring_assoc_array_ops);
  }
  
  /*
   * Describe a keyring for /proc.
   */
  static void keyring_describe(const struct key *keyring, struct seq_file *m)
  {
  	if (keyring->description)
  		seq_puts(m, keyring->description);
  	else
  		seq_puts(m, "[anon]");
  
  	if (key_is_positive(keyring)) {
  		if (keyring->keys.nr_leaves_on_tree != 0)
  			seq_printf(m, ": %lu", keyring->keys.nr_leaves_on_tree);
  		else
  			seq_puts(m, ": empty");
  	}
  }
  
  struct keyring_read_iterator_context {
  	size_t			buflen;
  	size_t			count;
  	key_serial_t __user	*buffer;
  };
  
  static int keyring_read_iterator(const void *object, void *data)
  {
  	struct keyring_read_iterator_context *ctx = data;
  	const struct key *key = keyring_ptr_to_key(object);
  	int ret;
  
  	kenter("{%s,%d},,{%zu/%zu}",
  	       key->type->name, key->serial, ctx->count, ctx->buflen);
  
  	if (ctx->count >= ctx->buflen)
  		return 1;
  
  	ret = put_user(key->serial, ctx->buffer);
  	if (ret < 0)
  		return ret;
  	ctx->buffer++;
  	ctx->count += sizeof(key->serial);
  	return 0;
  }
  
  /*
   * Read a list of key IDs from the keyring's contents in binary form
   *
   * The keyring's semaphore is read-locked by the caller.  This prevents someone
   * from modifying it under us - which could cause us to read key IDs multiple
   * times.
   */
  static long keyring_read(const struct key *keyring,
  			 char __user *buffer, size_t buflen)
  {
  	struct keyring_read_iterator_context ctx;
  	long ret;
  
  	kenter("{%d},,%zu", key_serial(keyring), buflen);
  
  	if (buflen & (sizeof(key_serial_t) - 1))
  		return -EINVAL;
  
  	/* Copy as many key IDs as fit into the buffer */
  	if (buffer && buflen) {
  		ctx.buffer = (key_serial_t __user *)buffer;
  		ctx.buflen = buflen;
  		ctx.count = 0;
  		ret = assoc_array_iterate(&keyring->keys,
  					  keyring_read_iterator, &ctx);
  		if (ret < 0) {
  			kleave(" = %ld [iterate]", ret);
  			return ret;
  		}
  	}
  
  	/* Return the size of the buffer needed */
  	ret = keyring->keys.nr_leaves_on_tree * sizeof(key_serial_t);
  	if (ret <= buflen)
  		kleave("= %ld [ok]", ret);
  	else
  		kleave("= %ld [buffer too small]", ret);
  	return ret;
  }
  
  /*
   * Allocate a keyring and link into the destination keyring.
   */
  struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
  			  const struct cred *cred, key_perm_t perm,
  			  unsigned long flags,
  			  struct key_restriction *restrict_link,
  			  struct key *dest)
  {
  	struct key *keyring;
  	int ret;
  
  	keyring = key_alloc(&key_type_keyring, description,
  			    uid, gid, cred, perm, flags, restrict_link);
  	if (!IS_ERR(keyring)) {
  		ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
  		if (ret < 0) {
  			key_put(keyring);
  			keyring = ERR_PTR(ret);
  		}
  	}
  
  	return keyring;
  }
  EXPORT_SYMBOL(keyring_alloc);
  
  /**
   * restrict_link_reject - Give -EPERM to restrict link
   * @keyring: The keyring being added to.
   * @type: The type of key being added.
   * @payload: The payload of the key intended to be added.
   * @data: Additional data for evaluating restriction.
   *
   * Reject the addition of any links to a keyring.  It can be overridden by
   * passing KEY_ALLOC_BYPASS_RESTRICTION to key_instantiate_and_link() when
   * adding a key to a keyring.
   *
   * This is meant to be stored in a key_restriction structure which is passed
   * in the restrict_link parameter to keyring_alloc().
   */
  int restrict_link_reject(struct key *keyring,
  			 const struct key_type *type,
  			 const union key_payload *payload,
  			 struct key *restriction_key)
  {
  	return -EPERM;
  }
  
  /*
   * By default, we keys found by getting an exact match on their descriptions.
   */
  bool key_default_cmp(const struct key *key,
  		     const struct key_match_data *match_data)
  {
  	return strcmp(key->description, match_data->raw_data) == 0;
  }
  
  /*
   * Iteration function to consider each key found.
   */
  static int keyring_search_iterator(const void *object, void *iterator_data)
  {
  	struct keyring_search_context *ctx = iterator_data;
  	const struct key *key = keyring_ptr_to_key(object);
  	unsigned long kflags = READ_ONCE(key->flags);
  	short state = READ_ONCE(key->state);
  
  	kenter("{%d}", key->serial);
  
  	/* ignore keys not of this type */
  	if (key->type != ctx->index_key.type) {
  		kleave(" = 0 [!type]");
  		return 0;
  	}
  
  	/* skip invalidated, revoked and expired keys */
  	if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
  		time_t expiry = READ_ONCE(key->expiry);
  
  		if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
  			      (1 << KEY_FLAG_REVOKED))) {
  			ctx->result = ERR_PTR(-EKEYREVOKED);
  			kleave(" = %d [invrev]", ctx->skipped_ret);
  			goto skipped;
  		}
  
  		if (expiry && ctx->now.tv_sec >= expiry) {
  			if (!(ctx->flags & KEYRING_SEARCH_SKIP_EXPIRED))
  				ctx->result = ERR_PTR(-EKEYEXPIRED);
  			kleave(" = %d [expire]", ctx->skipped_ret);
  			goto skipped;
  		}
  	}
  
  	/* keys that don't match */
  	if (!ctx->match_data.cmp(key, &ctx->match_data)) {
  		kleave(" = 0 [!match]");
  		return 0;
  	}
  
  	/* key must have search permissions */
  	if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
  	    key_task_permission(make_key_ref(key, ctx->possessed),
  				ctx->cred, KEY_NEED_SEARCH) < 0) {
  		ctx->result = ERR_PTR(-EACCES);
  		kleave(" = %d [!perm]", ctx->skipped_ret);
  		goto skipped;
  	}
  
  	if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
  		/* we set a different error code if we pass a negative key */
  		if (state < 0) {
  			ctx->result = ERR_PTR(state);
  			kleave(" = %d [neg]", ctx->skipped_ret);
  			goto skipped;
  		}
  	}
  
  	/* Found */
  	ctx->result = make_key_ref(key, ctx->possessed);
  	kleave(" = 1 [found]");
  	return 1;
  
  skipped:
  	return ctx->skipped_ret;
  }
  
  /*
   * Search inside a keyring for a key.  We can search by walking to it
   * directly based on its index-key or we can iterate over the entire
   * tree looking for it, based on the match function.
   */
  static int search_keyring(struct key *keyring, struct keyring_search_context *ctx)
  {
  	if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_DIRECT) {
  		const void *object;
  
  		object = assoc_array_find(&keyring->keys,
  					  &keyring_assoc_array_ops,
  					  &ctx->index_key);
  		return object ? ctx->iterator(object, ctx) : 0;
  	}
  	return assoc_array_iterate(&keyring->keys, ctx->iterator, ctx);
  }
  
  /*
   * Search a tree of keyrings that point to other keyrings up to the maximum
   * depth.
   */
  static bool search_nested_keyrings(struct key *keyring,
  				   struct keyring_search_context *ctx)
  {
  	struct {
  		struct key *keyring;
  		struct assoc_array_node *node;
  		int slot;
  	} stack[KEYRING_SEARCH_MAX_DEPTH];
  
  	struct assoc_array_shortcut *shortcut;
  	struct assoc_array_node *node;
  	struct assoc_array_ptr *ptr;
  	struct key *key;
  	int sp = 0, slot;
  
  	kenter("{%d},{%s,%s}",
  	       keyring->serial,
  	       ctx->index_key.type->name,
  	       ctx->index_key.description);
  
  #define STATE_CHECKS (KEYRING_SEARCH_NO_STATE_CHECK | KEYRING_SEARCH_DO_STATE_CHECK)
  	BUG_ON((ctx->flags & STATE_CHECKS) == 0 ||
  	       (ctx->flags & STATE_CHECKS) == STATE_CHECKS);
  
  	/* Check to see if this top-level keyring is what we are looking for
  	 * and whether it is valid or not.
  	 */
  	if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_ITERATE ||
  	    keyring_compare_object(keyring, &ctx->index_key)) {
  		ctx->skipped_ret = 2;
  		switch (ctx->iterator(keyring_key_to_ptr(keyring), ctx)) {
  		case 1:
  			goto found;
  		case 2:
  			return false;
  		default:
  			break;
  		}
  	}
  
  	ctx->skipped_ret = 0;
  
  	/* Start processing a new keyring */
  descend_to_keyring:
  	kdebug("descend to %d", keyring->serial);
  	if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
  			      (1 << KEY_FLAG_REVOKED)))
  		goto not_this_keyring;
  
  	/* Search through the keys in this keyring before its searching its
  	 * subtrees.
  	 */
  	if (search_keyring(keyring, ctx))
  		goto found;
  
  	/* Then manually iterate through the keyrings nested in this one.
  	 *
  	 * Start from the root node of the index tree.  Because of the way the
  	 * hash function has been set up, keyrings cluster on the leftmost
  	 * branch of the root node (root slot 0) or in the root node itself.
  	 * Non-keyrings avoid the leftmost branch of the root entirely (root
  	 * slots 1-15).
  	 */
  	ptr = READ_ONCE(keyring->keys.root);
  	if (!ptr)
  		goto not_this_keyring;
  
  	if (assoc_array_ptr_is_shortcut(ptr)) {
  		/* If the root is a shortcut, either the keyring only contains
  		 * keyring pointers (everything clusters behind root slot 0) or
  		 * doesn't contain any keyring pointers.
  		 */
  		shortcut = assoc_array_ptr_to_shortcut(ptr);
  		smp_read_barrier_depends();
  		if ((shortcut->index_key[0] & ASSOC_ARRAY_FAN_MASK) != 0)
  			goto not_this_keyring;
  
  		ptr = READ_ONCE(shortcut->next_node);
  		node = assoc_array_ptr_to_node(ptr);
  		goto begin_node;
  	}
  
  	node = assoc_array_ptr_to_node(ptr);
  	smp_read_barrier_depends();
  
  	ptr = node->slots[0];
  	if (!assoc_array_ptr_is_meta(ptr))
  		goto begin_node;
  
  descend_to_node:
  	/* Descend to a more distal node in this keyring's content tree and go
  	 * through that.
  	 */
  	kdebug("descend");
  	if (assoc_array_ptr_is_shortcut(ptr)) {
  		shortcut = assoc_array_ptr_to_shortcut(ptr);
  		smp_read_barrier_depends();
  		ptr = READ_ONCE(shortcut->next_node);
  		BUG_ON(!assoc_array_ptr_is_node(ptr));
  	}
  	node = assoc_array_ptr_to_node(ptr);
  
  begin_node:
  	kdebug("begin_node");
  	smp_read_barrier_depends();
  	slot = 0;
  ascend_to_node:
  	/* Go through the slots in a node */
  	for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
  		ptr = READ_ONCE(node->slots[slot]);
  
  		if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
  			goto descend_to_node;
  
  		if (!keyring_ptr_is_keyring(ptr))
  			continue;
  
  		key = keyring_ptr_to_key(ptr);
  
  		if (sp >= KEYRING_SEARCH_MAX_DEPTH) {
  			if (ctx->flags & KEYRING_SEARCH_DETECT_TOO_DEEP) {
  				ctx->result = ERR_PTR(-ELOOP);
  				return false;
  			}
  			goto not_this_keyring;
  		}
  
  		/* Search a nested keyring */
  		if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
  		    key_task_permission(make_key_ref(key, ctx->possessed),
  					ctx->cred, KEY_NEED_SEARCH) < 0)
  			continue;
  
  		/* stack the current position */
  		stack[sp].keyring = keyring;
  		stack[sp].node = node;
  		stack[sp].slot = slot;
  		sp++;
  
  		/* begin again with the new keyring */
  		keyring = key;
  		goto descend_to_keyring;
  	}
  
  	/* We've dealt with all the slots in the current node, so now we need
  	 * to ascend to the parent and continue processing there.
  	 */
  	ptr = READ_ONCE(node->back_pointer);
  	slot = node->parent_slot;
  
  	if (ptr && assoc_array_ptr_is_shortcut(ptr)) {
  		shortcut = assoc_array_ptr_to_shortcut(ptr);
  		smp_read_barrier_depends();
  		ptr = READ_ONCE(shortcut->back_pointer);
  		slot = shortcut->parent_slot;
  	}
  	if (!ptr)
  		goto not_this_keyring;
  	node = assoc_array_ptr_to_node(ptr);
  	smp_read_barrier_depends();
  	slot++;
  
  	/* If we've ascended to the root (zero backpointer), we must have just
  	 * finished processing the leftmost branch rather than the root slots -
  	 * so there can't be any more keyrings for us to find.
  	 */
  	if (node->back_pointer) {
  		kdebug("ascend %d", slot);
  		goto ascend_to_node;
  	}
  
  	/* The keyring we're looking at was disqualified or didn't contain a
  	 * matching key.
  	 */
  not_this_keyring:
  	kdebug("not_this_keyring %d", sp);
  	if (sp <= 0) {
  		kleave(" = false");
  		return false;
  	}
  
  	/* Resume the processing of a keyring higher up in the tree */
  	sp--;
  	keyring = stack[sp].keyring;
  	node = stack[sp].node;
  	slot = stack[sp].slot + 1;
  	kdebug("ascend to %d [%d]", keyring->serial, slot);
  	goto ascend_to_node;
  
  	/* We found a viable match */
  found:
  	key = key_ref_to_ptr(ctx->result);
  	key_check(key);
  	if (!(ctx->flags & KEYRING_SEARCH_NO_UPDATE_TIME)) {
  		key->last_used_at = ctx->now.tv_sec;
  		keyring->last_used_at = ctx->now.tv_sec;
  		while (sp > 0)
  			stack[--sp].keyring->last_used_at = ctx->now.tv_sec;
  	}
  	kleave(" = true");
  	return true;
  }
  
  /**
   * keyring_search_aux - Search a keyring tree for a key matching some criteria
   * @keyring_ref: A pointer to the keyring with possession indicator.
   * @ctx: The keyring search context.
   *
   * Search the supplied keyring tree for a key that matches the criteria given.
   * The root keyring and any linked keyrings must grant Search permission to the
   * caller to be searchable and keys can only be found if they too grant Search
   * to the caller. The possession flag on the root keyring pointer controls use
   * of the possessor bits in permissions checking of the entire tree.  In
   * addition, the LSM gets to forbid keyring searches and key matches.
   *
   * The search is performed as a breadth-then-depth search up to the prescribed
   * limit (KEYRING_SEARCH_MAX_DEPTH).
   *
   * Keys are matched to the type provided and are then filtered by the match
   * function, which is given the description to use in any way it sees fit.  The
   * match function may use any attributes of a key that it wishes to to
   * determine the match.  Normally the match function from the key type would be
   * used.
   *
   * RCU can be used to prevent the keyring key lists from disappearing without
   * the need to take lots of locks.
   *
   * Returns a pointer to the found key and increments the key usage count if
   * successful; -EAGAIN if no matching keys were found, or if expired or revoked
   * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
   * specified keyring wasn't a keyring.
   *
   * In the case of a successful return, the possession attribute from
   * @keyring_ref is propagated to the returned key reference.
   */
  key_ref_t keyring_search_aux(key_ref_t keyring_ref,
  			     struct keyring_search_context *ctx)
  {
  	struct key *keyring;
  	long err;
  
  	ctx->iterator = keyring_search_iterator;
  	ctx->possessed = is_key_possessed(keyring_ref);
  	ctx->result = ERR_PTR(-EAGAIN);
  
  	keyring = key_ref_to_ptr(keyring_ref);
  	key_check(keyring);
  
  	if (keyring->type != &key_type_keyring)
  		return ERR_PTR(-ENOTDIR);
  
  	if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM)) {
  		err = key_task_permission(keyring_ref, ctx->cred, KEY_NEED_SEARCH);
  		if (err < 0)
  			return ERR_PTR(err);
  	}
  
  	rcu_read_lock();
  	ctx->now = current_kernel_time();
  	if (search_nested_keyrings(keyring, ctx))
  		__key_get(key_ref_to_ptr(ctx->result));
  	rcu_read_unlock();
  	return ctx->result;
  }
  
  /**
   * keyring_search - Search the supplied keyring tree for a matching key
   * @keyring: The root of the keyring tree to be searched.
   * @type: The type of keyring we want to find.
   * @description: The name of the keyring we want to find.
   *
   * As keyring_search_aux() above, but using the current task's credentials and
   * type's default matching function and preferred search method.
   */
  key_ref_t keyring_search(key_ref_t keyring,
  			 struct key_type *type,
  			 const char *description)
  {
  	struct keyring_search_context ctx = {
  		.index_key.type		= type,
  		.index_key.description	= description,
  		.index_key.desc_len	= strlen(description),
  		.cred			= current_cred(),
  		.match_data.cmp		= key_default_cmp,
  		.match_data.raw_data	= description,
  		.match_data.lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
  		.flags			= KEYRING_SEARCH_DO_STATE_CHECK,
  	};
  	key_ref_t key;
  	int ret;
  
  	if (type->match_preparse) {
  		ret = type->match_preparse(&ctx.match_data);
  		if (ret < 0)
  			return ERR_PTR(ret);
  	}
  
  	key = keyring_search_aux(keyring, &ctx);
  
  	if (type->match_free)
  		type->match_free(&ctx.match_data);
  	return key;
  }
  EXPORT_SYMBOL(keyring_search);
  
  static struct key_restriction *keyring_restriction_alloc(
  	key_restrict_link_func_t check)
  {
  	struct key_restriction *keyres =
  		kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
  
  	if (!keyres)
  		return ERR_PTR(-ENOMEM);
  
  	keyres->check = check;
  
  	return keyres;
  }
  
  /*
   * Semaphore to serialise restriction setup to prevent reference count
   * cycles through restriction key pointers.
   */
  static DECLARE_RWSEM(keyring_serialise_restrict_sem);
  
  /*
   * Check for restriction cycles that would prevent keyring garbage collection.
   * keyring_serialise_restrict_sem must be held.
   */
  static bool keyring_detect_restriction_cycle(const struct key *dest_keyring,
  					     struct key_restriction *keyres)
  {
  	while (keyres && keyres->key &&
  	       keyres->key->type == &key_type_keyring) {
  		if (keyres->key == dest_keyring)
  			return true;
  
  		keyres = keyres->key->restrict_link;
  	}
  
  	return false;
  }
  
  /**
   * keyring_restrict - Look up and apply a restriction to a keyring
   *
   * @keyring: The keyring to be restricted
   * @restriction: The restriction options to apply to the keyring
   */
  int keyring_restrict(key_ref_t keyring_ref, const char *type,
  		     const char *restriction)
  {
  	struct key *keyring;
  	struct key_type *restrict_type = NULL;
  	struct key_restriction *restrict_link;
  	int ret = 0;
  
  	keyring = key_ref_to_ptr(keyring_ref);
  	key_check(keyring);
  
  	if (keyring->type != &key_type_keyring)
  		return -ENOTDIR;
  
  	if (!type) {
  		restrict_link = keyring_restriction_alloc(restrict_link_reject);
  	} else {
  		restrict_type = key_type_lookup(type);
  
  		if (IS_ERR(restrict_type))
  			return PTR_ERR(restrict_type);
  
  		if (!restrict_type->lookup_restriction) {
  			ret = -ENOENT;
  			goto error;
  		}
  
  		restrict_link = restrict_type->lookup_restriction(restriction);
  	}
  
  	if (IS_ERR(restrict_link)) {
  		ret = PTR_ERR(restrict_link);
  		goto error;
  	}
  
  	down_write(&keyring->sem);
  	down_write(&keyring_serialise_restrict_sem);
  
  	if (keyring->restrict_link)
  		ret = -EEXIST;
  	else if (keyring_detect_restriction_cycle(keyring, restrict_link))
  		ret = -EDEADLK;
  	else
  		keyring->restrict_link = restrict_link;
  
  	up_write(&keyring_serialise_restrict_sem);
  	up_write(&keyring->sem);
  
  	if (ret < 0) {
  		key_put(restrict_link->key);
  		kfree(restrict_link);
  	}
  
  error:
  	if (restrict_type)
  		key_type_put(restrict_type);
  
  	return ret;
  }
  EXPORT_SYMBOL(keyring_restrict);
  
  /*
   * Search the given keyring for a key that might be updated.
   *
   * The caller must guarantee that the keyring is a keyring and that the
   * permission is granted to modify the keyring as no check is made here.  The
   * caller must also hold a lock on the keyring semaphore.
   *
   * Returns a pointer to the found key with usage count incremented if
   * successful and returns NULL if not found.  Revoked and invalidated keys are
   * skipped over.
   *
   * If successful, the possession indicator is propagated from the keyring ref
   * to the returned key reference.
   */
  key_ref_t find_key_to_update(key_ref_t keyring_ref,
  			     const struct keyring_index_key *index_key)
  {
  	struct key *keyring, *key;
  	const void *object;
  
  	keyring = key_ref_to_ptr(keyring_ref);
  
  	kenter("{%d},{%s,%s}",
  	       keyring->serial, index_key->type->name, index_key->description);
  
  	object = assoc_array_find(&keyring->keys, &keyring_assoc_array_ops,
  				  index_key);
  
  	if (object)
  		goto found;
  
  	kleave(" = NULL");
  	return NULL;
  
  found:
  	key = keyring_ptr_to_key(object);
  	if (key->flags & ((1 << KEY_FLAG_INVALIDATED) |
  			  (1 << KEY_FLAG_REVOKED))) {
  		kleave(" = NULL [x]");
  		return NULL;
  	}
  	__key_get(key);
  	kleave(" = {%d}", key->serial);
  	return make_key_ref(key, is_key_possessed(keyring_ref));
  }
  
  /*
   * Find a keyring with the specified name.
   *
   * Only keyrings that have nonzero refcount, are not revoked, and are owned by a
   * user in the current user namespace are considered.  If @uid_keyring is %true,
   * the keyring additionally must have been allocated as a user or user session
   * keyring; otherwise, it must grant Search permission directly to the caller.
   *
   * Returns a pointer to the keyring with the keyring's refcount having being
   * incremented on success.  -ENOKEY is returned if a key could not be found.
   */
  struct key *find_keyring_by_name(const char *name, bool uid_keyring)
  {
  	struct key *keyring;
  	int bucket;
  
  	if (!name)
  		return ERR_PTR(-EINVAL);
  
  	bucket = keyring_hash(name);
  
  	read_lock(&keyring_name_lock);
  
  	if (keyring_name_hash[bucket].next) {
  		/* search this hash bucket for a keyring with a matching name
  		 * that's readable and that hasn't been revoked */
  		list_for_each_entry(keyring,
  				    &keyring_name_hash[bucket],
  				    name_link
  				    ) {
  			if (!kuid_has_mapping(current_user_ns(), keyring->user->uid))
  				continue;
  
  			if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
  				continue;
  
  			if (strcmp(keyring->description, name) != 0)
  				continue;
  
  			if (uid_keyring) {
  				if (!test_bit(KEY_FLAG_UID_KEYRING,
  					      &keyring->flags))
  					continue;
  			} else {
  				if (key_permission(make_key_ref(keyring, 0),
  						   KEY_NEED_SEARCH) < 0)
  					continue;
  			}
  
  			/* we've got a match but we might end up racing with
  			 * key_cleanup() if the keyring is currently 'dead'
  			 * (ie. it has a zero usage count) */
  			if (!refcount_inc_not_zero(&keyring->usage))
  				continue;
  			keyring->last_used_at = current_kernel_time().tv_sec;
  			goto out;
  		}
  	}
  
  	keyring = ERR_PTR(-ENOKEY);
  out:
  	read_unlock(&keyring_name_lock);
  	return keyring;
  }
  
  static int keyring_detect_cycle_iterator(const void *object,
  					 void *iterator_data)
  {
  	struct keyring_search_context *ctx = iterator_data;
  	const struct key *key = keyring_ptr_to_key(object);
  
  	kenter("{%d}", key->serial);
  
  	/* We might get a keyring with matching index-key that is nonetheless a
  	 * different keyring. */
  	if (key != ctx->match_data.raw_data)
  		return 0;
  
  	ctx->result = ERR_PTR(-EDEADLK);
  	return 1;
  }
  
  /*
   * See if a cycle will will be created by inserting acyclic tree B in acyclic
   * tree A at the topmost level (ie: as a direct child of A).
   *
   * Since we are adding B to A at the top level, checking for cycles should just
   * be a matter of seeing if node A is somewhere in tree B.
   */
  static int keyring_detect_cycle(struct key *A, struct key *B)
  {
  	struct keyring_search_context ctx = {
  		.index_key		= A->index_key,
  		.match_data.raw_data	= A,
  		.match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
  		.iterator		= keyring_detect_cycle_iterator,
  		.flags			= (KEYRING_SEARCH_NO_STATE_CHECK |
  					   KEYRING_SEARCH_NO_UPDATE_TIME |
  					   KEYRING_SEARCH_NO_CHECK_PERM |
  					   KEYRING_SEARCH_DETECT_TOO_DEEP),
  	};
  
  	rcu_read_lock();
  	search_nested_keyrings(B, &ctx);
  	rcu_read_unlock();
  	return PTR_ERR(ctx.result) == -EAGAIN ? 0 : PTR_ERR(ctx.result);
  }
  
  /*
   * Preallocate memory so that a key can be linked into to a keyring.
   */
  int __key_link_begin(struct key *keyring,
  		     const struct keyring_index_key *index_key,
  		     struct assoc_array_edit **_edit)
  	__acquires(&keyring->sem)
  	__acquires(&keyring_serialise_link_sem)
  {
  	struct assoc_array_edit *edit;
  	int ret;
  
  	kenter("%d,%s,%s,",
  	       keyring->serial, index_key->type->name, index_key->description);
  
  	BUG_ON(index_key->desc_len == 0);
  
  	if (keyring->type != &key_type_keyring)
  		return -ENOTDIR;
  
  	down_write(&keyring->sem);
  
  	ret = -EKEYREVOKED;
  	if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
  		goto error_krsem;
  
  	/* serialise link/link calls to prevent parallel calls causing a cycle
  	 * when linking two keyring in opposite orders */
  	if (index_key->type == &key_type_keyring)
  		down_write(&keyring_serialise_link_sem);
  
  	/* Create an edit script that will insert/replace the key in the
  	 * keyring tree.
  	 */
  	edit = assoc_array_insert(&keyring->keys,
  				  &keyring_assoc_array_ops,
  				  index_key,
  				  NULL);
  	if (IS_ERR(edit)) {
  		ret = PTR_ERR(edit);
  		goto error_sem;
  	}
  
  	/* If we're not replacing a link in-place then we're going to need some
  	 * extra quota.
  	 */
  	if (!edit->dead_leaf) {
  		ret = key_payload_reserve(keyring,
  					  keyring->datalen + KEYQUOTA_LINK_BYTES);
  		if (ret < 0)
  			goto error_cancel;
  	}
  
  	*_edit = edit;
  	kleave(" = 0");
  	return 0;
  
  error_cancel:
  	assoc_array_cancel_edit(edit);
  error_sem:
  	if (index_key->type == &key_type_keyring)
  		up_write(&keyring_serialise_link_sem);
  error_krsem:
  	up_write(&keyring->sem);
  	kleave(" = %d", ret);
  	return ret;
  }
  
  /*
   * Check already instantiated keys aren't going to be a problem.
   *
   * The caller must have called __key_link_begin(). Don't need to call this for
   * keys that were created since __key_link_begin() was called.
   */
  int __key_link_check_live_key(struct key *keyring, struct key *key)
  {
  	if (key->type == &key_type_keyring)
  		/* check that we aren't going to create a cycle by linking one
  		 * keyring to another */
  		return keyring_detect_cycle(keyring, key);
  	return 0;
  }
  
  /*
   * Link a key into to a keyring.
   *
   * Must be called with __key_link_begin() having being called.  Discards any
   * already extant link to matching key if there is one, so that each keyring
   * holds at most one link to any given key of a particular type+description
   * combination.
   */
  void __key_link(struct key *key, struct assoc_array_edit **_edit)
  {
  	__key_get(key);
  	assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key));
  	assoc_array_apply_edit(*_edit);
  	*_edit = NULL;
  }
  
  /*
   * Finish linking a key into to a keyring.
   *
   * Must be called with __key_link_begin() having being called.
   */
  void __key_link_end(struct key *keyring,
  		    const struct keyring_index_key *index_key,
  		    struct assoc_array_edit *edit)
  	__releases(&keyring->sem)
  	__releases(&keyring_serialise_link_sem)
  {
  	BUG_ON(index_key->type == NULL);
  	kenter("%d,%s,", keyring->serial, index_key->type->name);
  
  	if (index_key->type == &key_type_keyring)
  		up_write(&keyring_serialise_link_sem);
  
  	if (edit) {
  		if (!edit->dead_leaf) {
  			key_payload_reserve(keyring,
  				keyring->datalen - KEYQUOTA_LINK_BYTES);
  		}
  		assoc_array_cancel_edit(edit);
  	}
  	up_write(&keyring->sem);
  }
  
  /*
   * Check addition of keys to restricted keyrings.
   */
  static int __key_link_check_restriction(struct key *keyring, struct key *key)
  {
  	if (!keyring->restrict_link || !keyring->restrict_link->check)
  		return 0;
  	return keyring->restrict_link->check(keyring, key->type, &key->payload,
  					     keyring->restrict_link->key);
  }
  
  /**
   * key_link - Link a key to a keyring
   * @keyring: The keyring to make the link in.
   * @key: The key to link to.
   *
   * Make a link in a keyring to a key, such that the keyring holds a reference
   * on that key and the key can potentially be found by searching that keyring.
   *
   * This function will write-lock the keyring's semaphore and will consume some
   * of the user's key data quota to hold the link.
   *
   * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
   * -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
   * full, -EDQUOT if there is insufficient key data quota remaining to add
   * another link or -ENOMEM if there's insufficient memory.
   *
   * It is assumed that the caller has checked that it is permitted for a link to
   * be made (the keyring should have Write permission and the key Link
   * permission).
   */
  int key_link(struct key *keyring, struct key *key)
  {
  	struct assoc_array_edit *edit;
  	int ret;
  
  	kenter("{%d,%d}", keyring->serial, refcount_read(&keyring->usage));
  
  	key_check(keyring);
  	key_check(key);
  
  	ret = __key_link_begin(keyring, &key->index_key, &edit);
  	if (ret == 0) {
  		kdebug("begun {%d,%d}", keyring->serial, refcount_read(&keyring->usage));
  		ret = __key_link_check_restriction(keyring, key);
  		if (ret == 0)
  			ret = __key_link_check_live_key(keyring, key);
  		if (ret == 0)
  			__key_link(key, &edit);
  		__key_link_end(keyring, &key->index_key, edit);
  	}
  
  	kleave(" = %d {%d,%d}", ret, keyring->serial, refcount_read(&keyring->usage));
  	return ret;
  }
  EXPORT_SYMBOL(key_link);
  
  /**
   * key_unlink - Unlink the first link to a key from a keyring.
   * @keyring: The keyring to remove the link from.
   * @key: The key the link is to.
   *
   * Remove a link from a keyring to a key.
   *
   * This function will write-lock the keyring's semaphore.
   *
   * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
   * the key isn't linked to by the keyring or -ENOMEM if there's insufficient
   * memory.
   *
   * It is assumed that the caller has checked that it is permitted for a link to
   * be removed (the keyring should have Write permission; no permissions are
   * required on the key).
   */
  int key_unlink(struct key *keyring, struct key *key)
  {
  	struct assoc_array_edit *edit;
  	int ret;
  
  	key_check(keyring);
  	key_check(key);
  
  	if (keyring->type != &key_type_keyring)
  		return -ENOTDIR;
  
  	down_write(&keyring->sem);
  
  	edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops,
  				  &key->index_key);
  	if (IS_ERR(edit)) {
  		ret = PTR_ERR(edit);
  		goto error;
  	}
  	ret = -ENOENT;
  	if (edit == NULL)
  		goto error;
  
  	assoc_array_apply_edit(edit);
  	key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES);
  	ret = 0;
  
  error:
  	up_write(&keyring->sem);
  	return ret;
  }
  EXPORT_SYMBOL(key_unlink);
  
  /**
   * keyring_clear - Clear a keyring
   * @keyring: The keyring to clear.
   *
   * Clear the contents of the specified keyring.
   *
   * Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
   */
  int keyring_clear(struct key *keyring)
  {
  	struct assoc_array_edit *edit;
  	int ret;
  
  	if (keyring->type != &key_type_keyring)
  		return -ENOTDIR;
  
  	down_write(&keyring->sem);
  
  	edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
  	if (IS_ERR(edit)) {
  		ret = PTR_ERR(edit);
  	} else {
  		if (edit)
  			assoc_array_apply_edit(edit);
  		key_payload_reserve(keyring, 0);
  		ret = 0;
  	}
  
  	up_write(&keyring->sem);
  	return ret;
  }
  EXPORT_SYMBOL(keyring_clear);
  
  /*
   * Dispose of the links from a revoked keyring.
   *
   * This is called with the key sem write-locked.
   */
  static void keyring_revoke(struct key *keyring)
  {
  	struct assoc_array_edit *edit;
  
  	edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
  	if (!IS_ERR(edit)) {
  		if (edit)
  			assoc_array_apply_edit(edit);
  		key_payload_reserve(keyring, 0);
  	}
  }
  
  static bool keyring_gc_select_iterator(void *object, void *iterator_data)
  {
  	struct key *key = keyring_ptr_to_key(object);
  	time_t *limit = iterator_data;
  
  	if (key_is_dead(key, *limit))
  		return false;
  	key_get(key);
  	return true;
  }
  
  static int keyring_gc_check_iterator(const void *object, void *iterator_data)
  {
  	const struct key *key = keyring_ptr_to_key(object);
  	time_t *limit = iterator_data;
  
  	key_check(key);
  	return key_is_dead(key, *limit);
  }
  
  /*
   * Garbage collect pointers from a keyring.
   *
   * Not called with any locks held.  The keyring's key struct will not be
   * deallocated under us as only our caller may deallocate it.
   */
  void keyring_gc(struct key *keyring, time_t limit)
  {
  	int result;
  
  	kenter("%x{%s}", keyring->serial, keyring->description ?: "");
  
  	if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
  			      (1 << KEY_FLAG_REVOKED)))
  		goto dont_gc;
  
  	/* scan the keyring looking for dead keys */
  	rcu_read_lock();
  	result = assoc_array_iterate(&keyring->keys,
  				     keyring_gc_check_iterator, &limit);
  	rcu_read_unlock();
  	if (result == true)
  		goto do_gc;
  
  dont_gc:
  	kleave(" [no gc]");
  	return;
  
  do_gc:
  	down_write(&keyring->sem);
  	assoc_array_gc(&keyring->keys, &keyring_assoc_array_ops,
  		       keyring_gc_select_iterator, &limit);
  	up_write(&keyring->sem);
  	kleave(" [gc]");
  }
  
  /*
   * Garbage collect restriction pointers from a keyring.
   *
   * Keyring restrictions are associated with a key type, and must be cleaned
   * up if the key type is unregistered. The restriction is altered to always
   * reject additional keys so a keyring cannot be opened up by unregistering
   * a key type.
   *
   * Not called with any keyring locks held. The keyring's key struct will not
   * be deallocated under us as only our caller may deallocate it.
   *
   * The caller is required to hold key_types_sem and dead_type->sem. This is
   * fulfilled by key_gc_keytype() holding the locks on behalf of
   * key_garbage_collector(), which it invokes on a workqueue.
   */
  void keyring_restriction_gc(struct key *keyring, struct key_type *dead_type)
  {
  	struct key_restriction *keyres;
  
  	kenter("%x{%s}", keyring->serial, keyring->description ?: "");
  
  	/*
  	 * keyring->restrict_link is only assigned at key allocation time
  	 * or with the key type locked, so the only values that could be
  	 * concurrently assigned to keyring->restrict_link are for key
  	 * types other than dead_type. Given this, it's ok to check
  	 * the key type before acquiring keyring->sem.
  	 */
  	if (!dead_type || !keyring->restrict_link ||
  	    keyring->restrict_link->keytype != dead_type) {
  		kleave(" [no restriction gc]");
  		return;
  	}
  
  	/* Lock the keyring to ensure that a link is not in progress */
  	down_write(&keyring->sem);
  
  	keyres = keyring->restrict_link;
  
  	keyres->check = restrict_link_reject;
  
  	key_put(keyres->key);
  	keyres->key = NULL;
  	keyres->keytype = NULL;
  
  	up_write(&keyring->sem);
  
  	kleave(" [restriction gc]");
  }
  