Bluetooth: Fix response for mgmt_start_discovery when powered off

We should return a ENETDOWN status response if the adapter is powered
off (i.e. the HCI_UP flag isn't set).

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

net/bluetooth/mgmt.c

@@ -1619,6 +1619,11 @@ static int start_discovery(struct sock *sk, u16 index)
 
 	hci_dev_lock_bh(hdev);
 
+	if (!test_bit(HCI_UP, &hdev->flags)) {
+		err = cmd_status(sk, index, MGMT_OP_START_DISCOVERY, ENETDOWN);
+		goto failed;
+	}
+
 	cmd = mgmt_pending_add(sk, MGMT_OP_START_DISCOVERY, index, NULL, 0);
 	if (!cmd) {
 		err = -ENOMEM;