netfilter: x_tables: avoid warn and OOM killer on vmalloc call

Andrey Konovalov reported that this vmalloc call is based on an
userspace request and that it's spewing traces, which may flood the logs
and cause DoS if abused.

Florian Westphal also mentioned that this call should not trigger OOM
killer.

This patch brings the vmalloc call in sync to kmalloc and disables the
warn trace on allocation failure and also disable OOM killer invocation.

Note, however, that under such stress situation, other places may
trigger OOM killer invocation.

Change-Id: I488c42e18870e1b38efee56d3518bc3bc7457e53
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Git-commit: 5bad87348c70bb4d36e876523aade31e9dedd2fc
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git


Signed-off-by: Sean Tranchetti <stranche@codeaurora.org>
Signed-off-by: Chinmay Agarwal <chinagar@codeaurora.org>