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 int sco_send_frame(struct sock *sk, struct msghdr *msg, int len)
{
	struct sco_conn *conn = sco_pi(sk)->conn;
	struct sk_buff *skb;
	int err;

	/* Check outgoing MTU */
	if (len > conn->mtu)
		return -EINVAL;

	BT_DBG("sk %p len %d", sk, len);

	skb = bt_skb_send_alloc(sk, len, msg->msg_flags & MSG_DONTWAIT, &err);
	if (!skb)
		return err;

	if (memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len)) {
		kfree_skb(skb);
		return -EFAULT;
	}

	hci_send_sco(conn->hcon, skb);

	return len;
}

static int sco_send_frame(struct sock *sk, struct msghdr *msg, int len)
{
	struct sco_conn *conn = sco_pi(sk)->conn;
	struct sk_buff *skb;
	int err;

	/* Check outgoing MTU */
	if (len > conn->mtu)
		return -EINVAL;

	BT_DBG("sk %p len %d", sk, len);

	skb = bt_skb_send_alloc(sk, len, msg->msg_flags & MSG_DONTWAIT, &err);
	if (!skb)
		return err;

	if (memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len)) {
		kfree_skb(skb);
		return -EFAULT;
	}

	hci_send_sco(conn->hcon, skb);

	return len;
}
