Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 10 Nov 2020 08:16:55 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Cc:     Kleber Sacilotto de Souza <kleber.souza@canonical.com>,
        Eric Dumazet <edumazet@google.com>, netdev@vger.kernel.org,
        Gerrit Renker <gerrit@erg.abdn.ac.uk>,
        "David S. Miller" <davem@davemloft.net>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        "Alexander A. Klimov" <grandmaster@al2klimov.de>,
        Kees Cook <keescook@chromium.org>,
        Alexey Kodanev <alexey.kodanev@oracle.com>,
        dccp@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] dccp: ccid: move timers to struct dccp_sock
Message-ID: <20201110081655.29cbcd34@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
In-Reply-To: <20201110111932.GS595944@mussarela>
References: <20201013171849.236025-1-kleber.souza@canonical.com>
        <20201013171849.236025-2-kleber.souza@canonical.com>
        <20201016153016.04bffc1e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
        <20201109114828.GP595944@mussarela>
        <20201109094938.45b230c9@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
        <20201109210909.GQ595944@mussarela>
        <20201109131554.5f65b2fa@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
        <20201109213134.GR595944@mussarela>
        <20201109141553.30e9d502@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
        <20201110111932.GS595944@mussarela>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

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.