Bluetooth: RFCOMM - Fix missing msg_namelen update in rfcomm_sock_recvmsg()

If RFCOMM_DEFER_SETUP is set in the flags, rfcomm_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_stream_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>
void __exit rfcomm_cleanup_sockets(void)
{
	bt_procfs_cleanup(&init_net, "rfcomm");

	debugfs_remove(rfcomm_sock_debugfs);

	if (bt_sock_unregister(BTPROTO_RFCOMM) < 0)
		BT_ERR("RFCOMM socket layer unregistration failed");

	proto_unregister(&rfcomm_proto);
}

void __exit rfcomm_cleanup_sockets(void)
{
	bt_procfs_cleanup(&init_net, "rfcomm");

	debugfs_remove(rfcomm_sock_debugfs);

	if (bt_sock_unregister(BTPROTO_RFCOMM) < 0)
		BT_ERR("RFCOMM socket layer unregistration failed");

	proto_unregister(&rfcomm_proto);
}
