Bluetooth: Disabling discoverable with timeout is invalid

Add one extra sanity check to ensure that the supplied timeout value is
actually valid in this context.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>

net/bluetooth/mgmt.c

@@ -850,13 +850,16 @@ static int set_discoverable(struct sock *sk, u16 index, void *data, u16 len)
 		return cmd_status(sk, index, MGMT_OP_SET_DISCOVERABLE,
 						MGMT_STATUS_INVALID_PARAMS);
 
+	timeout = get_unaligned_le16(&cp->timeout);
+	if (!cp->val && timeout > 0)
+		return cmd_status(sk, index, MGMT_OP_SET_DISCOVERABLE,
+						MGMT_STATUS_INVALID_PARAMS);
+
 	hdev = hci_dev_get(index);
 	if (!hdev)
 		return cmd_status(sk, index, MGMT_OP_SET_DISCOVERABLE,
 						MGMT_STATUS_INVALID_PARAMS);
 
-	timeout = get_unaligned_le16(&cp->timeout);
-
 	hci_dev_lock(hdev);
 
 	if (!hdev_is_powered(hdev) && timeout > 0) {