commit b8216468 upstream.

Add validation code into mISDN/socket.c
Signed-off-by: Emrah Demir <ed@abdsec.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>