netdev - Re: Yet another bridge netfilter crash

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Message-ID: <4C49A4C6.4070503@trash.net>
Date:	Fri, 23 Jul 2010 16:18:46 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Herbert Xu <herbert@...dor.apana.org.au>
CC:	Stephen Hemminger <shemminger@...tta.com>, netdev@...r.kernel.org
Subject: Re: Yet another bridge netfilter crash

On 23.07.2010 15:42, Herbert Xu wrote:
> Hi:
> 
> I was cced on the following bug:
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=617268
> 
>>>From what I've seen in the crash dump, this would appear to be
> yet another manifestation of the evil relationship between the
> bridge and IPv4 through netfilter.
> 
> In particular, bridge netfilter invokes IPv4's PRE_ROUTING rules,
> one of which assembles packets for connection tracking.
> 
> Unfortunately, the same cache is used for reassembling bridge
> packets and non-bridge packets.
> 
> Now we already knew about this and its potential security effects.
> However, what we didn't know is that this can also cause a packet
> to appear in the bridge pre_routing code with nf_bridge set to
> NULL when it must not be NULL.
> 
> This happens if the non-bridge fragment appeared first.
> 
> So now is the time to fix this properly by giving the bridge its
> own separate conntrack namespace/zone.

I think we've already fixed this by commit 8fa9ff6:


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