netfilter: ctnetlink: don't permit ct creation with random tuple

netfilter: ctnetlink: don't permit ct creation with random tuple

commit 442fad9423b78319e0019a7f5047eddf3317afbc upstream.

Userspace can cause kernel panic by not specifying orig/reply
tuple: kernel will create a tuple with random stack values.

Problem is that tuple.dst.dir will be random, too, which
causes nf_ct_tuplehash_to_ctrack() to return garbage.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@gnumonks.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>