netdev - Re: [PATCH 2/2] neighbour: allow NUD_NOARP entries to be forced GCed

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Date:   Mon, 19 Apr 2021 21:27:13 -0700
From:   David Ahern <dsahern@...il.com>
To:     Kasper Dupont <kasperd@...fm.28.feb.2009.kasperd.net>
Cc:     netdev@...r.kernel.org,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>,
        davem@...emloft.net, kuba@...nel.org, dsahern@...nel.org,
        Kasper Dupont <kasperd@...wv.06.feb.2021.kasperd.net>
Subject: Re: [PATCH 2/2] neighbour: allow NUD_NOARP entries to be forced GCed

On 4/19/21 10:52 AM, Kasper Dupont wrote:
> On 19/04/21 10.10, David Ahern wrote:
>> On 4/19/21 9:44 AM, Kasper Dupont wrote:
>>>
>>> Is there any update regarding this change?
>>>
>>> I noticed this regression when it was used in a DoS attack on one of
>>> my servers which I had upgraded from Ubuntu 18.04 to 20.04.
>>>
>>> I have verified that Ubuntu 18.04 is not subject to this attack and
>>> Ubuntu 20.04 is vulnerable. I have also verified that the one-line
>>> change which Cascardo has provided fixes the vulnerability on Ubuntu
>>> 20.04.
>>>
>>
>> your testing included both patches or just this one?
> 
> I applied only this one line change on top of the kernel in Ubuntu
> 20.04. The behavior I observed was that without the patch the kernel
> was vulnerable and with that patch I was unable to reproduce the
> problem.

This patch should be re-submitted standalone for -net

> 
> The other longer patch is for a different issue which Cascardo
> discovered while working on the one I had reported. I don't have an
> environment set up where I can reproduce the issue addressed by that
> larger patch.
> 

The first patch is the one I have concerns about.