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Commit e59428f7 authored by David Howells's avatar David Howells
Browse files

keys: Move the RCU locks outwards from the keyring search functions 



Move the RCU locks outwards from the keyring search functions so that it
will become possible to provide an RCU-capable partial request_key()
function in a later commit.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent a09003b5

Documentation/security/keys/request-key.rst

+1 −1
Original line number Diff line number Diff line
@@ -148,7 +148,7 @@ The Search Algorithm 


A search of any particular keyring proceeds in the following fashion:



  1) When the key management code searches for a key (keyring_search_aux) it

  1) When the key management code searches for a key (keyring_search_rcu) it

     firstly calls key_permission(SEARCH) on the keyring it's starting with,

     if this denies permission, it doesn't search further.

include/keys/request_key_auth-type.h

+1 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
 * Authorisation record for request_key().

 */

struct request_key_auth {

	struct rcu_head		rcu;

	struct key		*target_key;

	struct key		*dest_keyring;

	const struct cred	*cred;

security/keys/internal.h

+3 −3
Original line number Diff line number Diff line
@@ -139,11 +139,11 @@ struct keyring_search_context { 


extern bool key_default_cmp(const struct key *key,

			    const struct key_match_data *match_data);

extern key_ref_t keyring_search_aux(key_ref_t keyring_ref,

extern key_ref_t keyring_search_rcu(key_ref_t keyring_ref,

				    struct keyring_search_context *ctx);



extern key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx);

extern key_ref_t search_process_keyrings(struct keyring_search_context *ctx);

extern key_ref_t search_cred_keyrings_rcu(struct keyring_search_context *ctx);

extern key_ref_t search_process_keyrings_rcu(struct keyring_search_context *ctx);



extern struct key *find_keyring_by_name(const char *name, bool uid_keyring);

security/keys/keyring.c

+9 −7
Original line number Diff line number Diff line
@@ -835,7 +835,7 @@ static bool search_nested_keyrings(struct key *keyring, 
}



/**

 * keyring_search_aux - Search a keyring tree for a key matching some criteria

 * keyring_search_rcu - Search a keyring tree for a matching key under RCU

 * @keyring_ref: A pointer to the keyring with possession indicator.

 * @ctx: The keyring search context.

 *
@@ -847,7 +847,9 @@ static bool search_nested_keyrings(struct key *keyring, 
 * 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).

 * limit (KEYRING_SEARCH_MAX_DEPTH).  The caller must hold the RCU read lock to

 * prevent keyrings from being destroyed or rearranged whilst they are being

 * searched.

 *

 * 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
@@ -866,7 +868,7 @@ static bool search_nested_keyrings(struct key *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,

key_ref_t keyring_search_rcu(key_ref_t keyring_ref,

			     struct keyring_search_context *ctx)

{

	struct key *keyring;
@@ -888,11 +890,9 @@ key_ref_t keyring_search_aux(key_ref_t keyring_ref, 
			return ERR_PTR(err);

	}



	rcu_read_lock();

	ctx->now = ktime_get_real_seconds();

	if (search_nested_keyrings(keyring, ctx))

		__key_get(key_ref_to_ptr(ctx->result));

	rcu_read_unlock();

	return ctx->result;

}
@@ -902,7 +902,7 @@ key_ref_t keyring_search_aux(key_ref_t keyring_ref, 
 * @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

 * As keyring_search_rcu() 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,
@@ -928,7 +928,9 @@ key_ref_t keyring_search(key_ref_t keyring, 
			return ERR_PTR(ret);

	}



	key = keyring_search_aux(keyring, &ctx);

	rcu_read_lock();

	key = keyring_search_rcu(keyring, &ctx);

	rcu_read_unlock();



	if (type->match_free)

		type->match_free(&ctx.match_data);

security/keys/proc.c

+3 −1
Original line number Diff line number Diff line
@@ -179,7 +179,9 @@ static int proc_keys_show(struct seq_file *m, void *v) 
	 * skip if the key does not indicate the possessor can view it

	 */

	if (key->perm & KEY_POS_VIEW) {

		skey_ref = search_my_process_keyrings(&ctx);

		rcu_read_lock();

		skey_ref = search_cred_keyrings_rcu(&ctx);

		rcu_read_unlock();

		if (!IS_ERR(skey_ref)) {

			key_ref_put(skey_ref);

			key_ref = make_key_ref(key, 1);