Bluetooth: SCO - Fix missing msg_namelen update in sco_sock_recvmsg()

If the socket is in state BT_CONNECT2 and BT_SK_DEFER_SETUP is set in
the flags, sco_sock_recvmsg() returns early with 0 without updating the
possibly set msg_namelen member. This, in turn, leads to a 128 byte
kernel stack leak in net/socket.c.

Fix this by updating msg_namelen in this case. For all other cases it
will be handled in bt_sock_recvmsg().

Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Gustavo Padovan <gustavo@padovan.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bluetooth/sco.c

@@ -665,6 +665,7 @@ static int sco_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 	    test_bit(BT_SK_DEFER_SETUP, &bt_sk(sk)->flags)) {
 		hci_conn_accept(pi->conn->hcon, 0);
 		sk->sk_state = BT_CONFIG;
+		msg->msg_namelen = 0;
 
 		release_sock(sk);
 		return 0;