KEYS: Add an optional lookup_restriction hook to key_type

The restrict_link functions used to validate keys as they are linked
to a keyring can be associated with specific key types.  Each key type
may be loaded (or not) at runtime, so lookup of restrict_link
functions needs to be part of the key type implementation to ensure
that the requested keys can be examined.

Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/key-type.h b/include/linux/key-type.h
index eaee981c5558..8496cf64575c 100644
--- a/include/linux/key-type.h
+++ b/include/linux/key-type.h
@@ -147,6 +147,14 @@ struct key_type {
 	 */
 	request_key_actor_t request_key;
 
+	/* Look up a keyring access restriction (optional)
+	 *
+	 * - NULL is a valid return value (meaning the requested restriction
+	 *   is known but will never block addition of a key)
+	 * - should return -EINVAL if the restriction is unknown
+	 */
+	struct key_restriction *(*lookup_restriction)(const char *params);
+
 	/* internal fields */
 	struct list_head	link;		/* link in types list */
 	struct lock_class_key	lock_class;	/* key->sem lock class */