netfilter: ipt_ULOG: fix info leaks

commit 278f2b3e2af5f32ea1afe34fa12a2518153e6e49 upstream.

The ulog messages leak heap bytes by the means of padding bytes and
incompletely filled string arrays. Fix those by memset(0)'ing the
whole struct before filling it.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Jan Tore Morken <jantore@morken.priv.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>