netfilter: ebtables: CONFIG_COMPAT: don't trust userland offsets

netfilter: ebtables: CONFIG_COMPAT: don't trust userland offsets

We need to make sure the offsets are not out of range of the
total size.
Also check that they are in ascending order.

The WARN_ON triggered by syzkaller (it sets panic_on_warn) is
changed to also bail out, no point in continuing parsing.

Briefly tested with simple ruleset of
-A INPUT --limit 1/s' --log
plus jump to custom chains using 32bit ebtables binary.

Reported-by: <syzbot+845a53d13171abf8bf29@syzkaller.appspotmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
(cherry picked from commit b71812168571fa55e44cdd0254471331b9c4c4c6)

Orabug: 27774012
CVE: CVE-2018-1068

Signed-off-by: Tim Tianyang Chen <tianyang.chen@oracle.com>
Reviewed-by: Chuck Anderson <chuck.anderson@oracle.com>