KEYS: Give key types their own lockdep class for key->sem

Give keys their own lockdep class to differentiate them from each other in case
a key of one type has to refer to a key of another type.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

include/linux/key-type.h

@@ -92,6 +92,7 @@ struct key_type {
 
 	/* internal fields */
 	struct list_head	link;		/* link in types list */
+	struct lock_class_key	lock_class;	/* key->sem lock class */
 };
 
 extern struct key_type key_type_keyring;

security/keys/key.c

@@ -291,6 +291,7 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 
 	atomic_set(&key->usage, 1);
 	init_rwsem(&key->sem);
+	lockdep_set_class(&key->sem, &type->lock_class);
 	key->type = type;
 	key->user = user;
 	key->quotalen = quotalen;
@@ -946,6 +947,8 @@ int register_key_type(struct key_type *ktype)
 	struct key_type *p;
 	int ret;
 
+	memset(&ktype->lock_class, 0, sizeof(ktype->lock_class));
+
 	ret = -EEXIST;
 	down_write(&key_types_sem);