From mboxrd@z Thu Jan  1 00:00:00 1970
From: Willem de Bruijn <willemb@google.com>
Subject: Re: [PATCH net] udp: prevent bugcheck if filter truncates packet too much
Date: Sat, 9 Jul 2016 09:05:23 -0400
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References: <20160708155233.C78AAA0ECC@unicorn.suse.cz> <1468020700.30694.38.camel@edumazet-glaptop3.roam.corp.google.com>
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Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	samanthakumar <samanthakumar@google.com>,
	Marco Grassi <marco.gra@gmail.com>,
	Network Development <netdev@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	James Morris <jmorris@namei.org>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	Patrick McHardy <kaber@trash.net>
To: Michal Kubecek <mkubecek@suse.cz>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20160709104340.GA9637@unicorn.suse.cz>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: netdev.vger.kernel.org

On Sat, Jul 9, 2016 at 6:43 AM, Michal Kubecek <mkubecek@suse.cz> wrote:
> On Sat, Jul 09, 2016 at 11:48:49AM +0200, Daniel Borkmann wrote:
>> On 07/09/2016 02:20 AM, Alexei Starovoitov wrote:
>> >On Sat, Jul 09, 2016 at 01:31:40AM +0200, Eric Dumazet wrote:
>> >>On Fri, 2016-07-08 at 17:52 +0200, Michal Kubecek wrote:
>> >>>If socket filter truncates an udp packet below the length of UDP header
>> >>>in udpv6_queue_rcv_skb() or udp_queue_rcv_skb(), it will trigger a
>> >>>BUG_ON in skb_pull_rcsum(). This BUG_ON (and therefore a system crash if
>> >>>kernel is configured that way) can be easily enforced by an unprivileged
>> >>>user which was reported as CVE-2016-6162. For a reproducer, see
>> >>>http://seclists.org/oss-sec/2016/q3/8
>> >>>
>> >>>Fixes: e6afc8ace6dd ("udp: remove headers from UDP packets before queueing")
>> >>>Reported-by: Marco Grassi <marco.gra@gmail.com>
>> >>>Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
>> >>>---
>
>> >>Acked-by: Eric Dumazet <edumazet@google.com>
>> >
>> >this is incomplete fix. Please do not apply. See discussion at security@kernel
>>
>> Ohh well, didn't see it earlier before starting the discussion at security@...
>>
>> I'm okay if we take this for now as a quick band aid and find a better
>> way how to deal with the underlying issue long-term so that it's
>> /guaranteed/ that it doesn't bite us any further in such fragile ways.
>
> Agreed. As rc7 is due in a day or two, rushing a complex and intrusive
> solution in might be too risky.

Acked-by: Willem de Bruijn <willemb@google.com>

Thanks, Michal.