netdev - Re: [PATCH nf] netfilter: bridge: ebt_among: add missing match size checks

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Message-ID: <20180225190445.ixdsjfe6ri57nlpe@salvia>
Date:   Sun, 25 Feb 2018 20:04:45 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Florian Westphal <fw@...len.de>
Cc:     netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
        bridge@...ts.linux-foundation.org, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH nf] netfilter: bridge: ebt_among: add missing match size
 checks

On Mon, Feb 19, 2018 at 03:01:45AM +0100, Florian Westphal wrote:
> ebt_among is special, it has a dynamic match size and is exempt
> from the central size checks.
> 
> Therefore it must check that the size of the match structure
> provided from userspace is sane by making sure em->match_size
> is at least the minimum size of the expected structure.
> 
> The module has such a check, but its only done after accessing
> a structure that might be out of bounds.
> 
> tested with: ebtables -A INPUT ... \
> --among-dst fe:fe:fe:fe:fe:fe
> --among-dst fe:fe:fe:fe:fe:fe --among-src fe:fe:fe:fe:ff:f,fe:fe:fe:fe:fe:fb,fe:fe:fe:fe:fc:fd,fe:fe:fe:fe:fe:fd,fe:fe:fe:fe:fe:fe
> --among-src fe:fe:fe:fe:ff:f,fe:fe:fe:fe:fe:fa,fe:fe:fe:fe:fe:fd,fe:fe:fe:fe:fe:fe,fe:fe:fe:fe:fe:fe

Applied, thanks Florian.