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

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Message-ID: <bda042e0-8054-41f3-5df6-c39ad424cde2@oracle.com>
Date:   Mon, 29 Aug 2022 09:10:10 -0500
From:   john.p.donnelly@...cle.com
To:     Florian Westphal <fw@...len.de>
Cc:     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

On 8/29/22 9:03 AM, Florian Westphal wrote:
> 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://urldefense.com/v3/__https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7997eff82828304b780dc0a39707e1946d6f1ebf__;!!ACWV5N9M2RV99hQ!JxonjgQUi7Mbcd-ouxRwPgu8Jwl6ej2rO4pTvYMtteWexclV5-hciu9e5rgtkXoB7dyAdLCyZ4EQ9HQj$

Thank you !