Add missing sizecheckings. Thanks Patrick Mchardy for the hint. This
patch requires the previous (7/8), otherwise it would break ctnetlink.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

-- 
The dawn of the fourth age of Linux firewalling is coming; a time of
great struggle and heroic deeds -- J.Kadlecsik got inspired by J.Morris