netdev - Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8

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Date:   Mon, 03 Apr 2017 05:09:03 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Denys Fedoryshchenko <nuclearcat@...learcat.com>
Cc:     Florian Westphal <fw@...len.de>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Patrick McHardy <kaber@...sh.net>,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        linux-kernel@...r.kernel.org, netdev-owner@...r.kernel.org
Subject: Re: KASAN, xt_TCPMSS  finally found nasty use-after-free bug? 4.10.8

On Mon, 2017-04-03 at 11:10 +0300, Denys Fedoryshchenko wrote:

> I modified patch a little as:
> if (th->doff * 4 < sizeof(_tcph)) {
>   par->hotdrop = true;
>   WARN_ON_ONCE(!tcpinfo->option);
>   return false;
> }
> 
> And it did triggered WARN once at morning, and didn't hit KASAN. I will 
> run for a while more, to see if it is ok, and then if stable, will try 
> to enable SFQ again.

Excellent news !
We will post an official fix today, thanks a lot for this detective work
Denys.