linux-kernel - Re: [PATCH nf] netfilter: ebtables: reject blobs that don't provide all entry points

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Message-ID: <20220829140320.GB27814@breakpoint.cc>
Date:   Mon, 29 Aug 2022 16:03:20 +0200
From:   Florian Westphal <fw@...len.de>
To:     john.p.donnelly@...cle.com
Cc:     Florian Westphal <fw@...len.de>, netfilter-devel@...r.kernel.org,
        syzkaller@...glegroups.com, george.kennedy@...cle.com,
        vegard.nossum@...cle.com, bridge@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
Subject: Re: [PATCH nf] netfilter: ebtables: reject blobs that don't provide
 all entry points

john.p.donnelly@...cle.com <john.p.donnelly@...cle.com> wrote:
> On 8/20/22 12:35 PM, Florian Westphal wrote:
> > For some reason ebtables reject blobs that provide entry points that are
> > not supported by the table.
> > 
> > What it should instead reject is the opposite, i.e. rulesets that
> > DO NOT provide an entry point that is supported by the table.
> > 
> > t->valid_hooks is the bitmask of hooks (input, forward ...) that will
> > see packets.  So, providing an entry point that is not support is
> > harmless (never called/used), but the reverse is NOT, this will cause
> > crash because the ebtables traverser doesn't expect a NULL blob for
> > a location its receiving packets for.
> > 
> > Instead of fixing all the individual checks, do what iptables is doing and
> > reject all blobs that doesn't provide the expected hooks.
> > 
> > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> > Reported-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
> > Signed-off-by: Florian Westphal <fw@...len.de>
> 
> Hi,
> 
>  Could you please add the panic stack mentioned above  and syzkaller
> reproducer ID to the commit text ?

I did not see a reproducer ID.  What ended up in the tree is this:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7997eff82828304b780dc0a39707e1946d6f1ebf