KEYS: Search for auth-key by name rather than target key ID

Search for auth-key by name rather than by target key ID as, in a future
patch, we'll by searching directly by index key in preference to iteration
over all keys.

Signed-off-by: David Howells <dhowells@redhat.com>

security/keys/request_key_auth.c

@@ -18,6 +18,7 @@
 #include <linux/slab.h>
 #include <asm/uaccess.h>
 #include "internal.h"
+#include <keys/user-type.h>
 
 static int request_key_auth_instantiate(struct key *,
 					struct key_preparsed_payload *);
@@ -221,34 +222,26 @@ error_alloc:
 	return ERR_PTR(ret);
 }
 
-/*
- * See if an authorisation key is associated with a particular key.
- */
-static int key_get_instantiation_authkey_match(const struct key *key,
-					       const void *_id)
-{
-	struct request_key_auth *rka = key->payload.data;
-	key_serial_t id = (key_serial_t)(unsigned long) _id;
-
-	return rka->target_key->serial == id;
-}
-
 /*
  * Search the current process's keyrings for the authorisation key for
  * instantiation of a key.
  */
 struct key *key_get_instantiation_authkey(key_serial_t target_id)
 {
+	char description[16];
 	struct keyring_search_context ctx = {
 		.index_key.type		= &key_type_request_key_auth,
+		.index_key.description	= description,
 		.cred			= current_cred(),
-		.match			= key_get_instantiation_authkey_match,
-		.match_data		= (void *)(unsigned long)target_id,
+		.match			= user_match,
+		.match_data		= description,
 		.flags			= KEYRING_SEARCH_LOOKUP_DIRECT,
 	};
 	struct key *authkey;
 	key_ref_t authkey_ref;
 
+	sprintf(description, "%x", target_id);
+
 	authkey_ref = search_process_keyrings(&ctx);
 
 	if (IS_ERR(authkey_ref)) {