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 <[e-mail]>
Acked-by: Mimi Zohar <[e-mail]>
Signed-off-by: James Morris <[e-mail]>

include/linux/key-type.h

···
 
 	/* 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

···
 
 	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;
···
 {
 	struct key_type *p;
 	int ret;
+
+	memset(&ktype->lock_class, 0, sizeof(ktype->lock_class));
 
 	ret = -EEXIST;
 	down_write(&key_types_sem);