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>
static void sco_sock_init(struct sock *sk, struct sock *parent)
{
	BT_DBG("sk %p", sk);

	if (parent) {
		sk->sk_type = parent->sk_type;
		bt_sk(sk)->flags = bt_sk(parent)->flags;
		security_sk_clone(parent, sk);
	}
}

static void sco_sock_init(struct sock *sk, struct sock *parent)
{
	BT_DBG("sk %p", sk);

	if (parent) {
		sk->sk_type = parent->sk_type;
		bt_sk(sk)->flags = bt_sk(parent)->flags;
		security_sk_clone(parent, sk);
	}
}
