Bluetooth: Fix old_key_type logic for non-persistent keys

Even if there's no previous key stored the connection might still be
secured with a non-persistent key and in that case the key type in the
hci_conn struct should be checked.
Signed-off-by: Johan Hedberg <johan.hedberg@nokia.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

net/bluetooth/hci_core.c

@@ -1069,7 +1069,7 @@ int hci_add_link_key(struct hci_dev *hdev, struct hci_conn *conn, int new_key,
 		old_key_type = old_key->type;
 		key = old_key;
 	} else {
-		old_key_type = 0xff;
+		old_key_type = conn ? conn->key_type : 0xff;
 		key = kzalloc(sizeof(*key), GFP_ATOMIC);
 		if (!key)
 			return -ENOMEM;