linux-kernel - Re: [PATCH 1/2] dccp: ccid: move timers to struct dccp

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Message-ID: <20201110081655.29cbcd34@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Tue, 10 Nov 2020 08:16:55 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Cc:     Kleber Sacilotto de Souza <kleber.souza@...onical.com>,
        Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
        Gerrit Renker <gerrit@....abdn.ac.uk>,
        "David S. Miller" <davem@...emloft.net>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        "Alexander A. Klimov" <grandmaster@...klimov.de>,
        Kees Cook <keescook@...omium.org>,
        Alexey Kodanev <alexey.kodanev@...cle.com>,
        dccp@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dccp: ccid: move timers to struct dccp_sock

On Tue, 10 Nov 2020 08:19:32 -0300 Thadeu Lima de Souza Cascardo wrote:
> Yeah, I agree with your initial email. The patch I submitted for that fix needs
> rework, which is what I tried and failed so far. I need to get back to some
> testing of my latest fix and find out what needs fixing there.
> 
> But I am also saying that simply doing a del_timer_sync on disconnect paths
> won't do, because there are non-disconnect paths where there is a CCID that we
> will remove and replace and that will still trigger a timer UAF.
> 
> So I have been working on a fix that involves a refcnt on ccid itself. But I
> want to test that it really fixes the problem and I have spent most of the time
> finding out a way to trigger the timer in a race with the disconnect path.

Sounds good, thanks a lot for working on this!

> And that same test has showed me that this timer UAF will happen regardless of
> commit 2677d20677314101293e6da0094ede7b5526d2b1, which led me into stating that
> reverting it should be done in any case.
> 
> I think I can find some time this week to work a little further on the fix for
> the time UAF.