linux-kernel - Re: KVM induced panic on 2.6.38[2367] & 2.6.39

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Message-ID: <4DEEBFC2.4060102@fnarfbargle.com>
Date:	Wed, 08 Jun 2011 08:18:10 +0800
From:	Brad Campbell <brad@...rfbargle.com>
To:	Patrick McHardy <kaber@...sh.net>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	Bart De Schuymer <bdschuym@...dora.be>, kvm@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: KVM induced panic on 2.6.38[2367] & 2.6.39

On 08/06/11 06:57, Patrick McHardy wrote:
> On 07.06.2011 20:31, Eric Dumazet wrote:
>> Le mardi 07 juin 2011 à 17:35 +0200, Patrick McHardy a écrit :
>>
>>> The main suspects would be NAT and TCPMSS. Did you also try whether
>>> the crash occurs with only one of these these rules?
>>>
>>>> I've just compiled out CONFIG_BRIDGE_NETFILTER and can no longer access
>>>> the address the way I was doing it, so that's a no-go for me.
>>>
>>> That's really weird since you're apparently not using any bridge
>>> netfilter features. It shouldn't have any effect besides changing
>>> at which point ip_tables is invoked. How are your network devices
>>> configured (specifically any bridges)?
>>
>> Something in the kernel does
>>
>> u16 *ptr = addr (given by kmalloc())
>>
>> ptr[-1] = 0;
>>
>> Could be an off-one error in a memmove()/memcopy() or loop...
>>
>> I cant see a network issue here.
>
> So far me neither, but netfilter appears to trigger the bug.

Would it help if I tried some older kernels? This issue only surfaced 
for me recently as I only installed the VM's in question about 12 weeks 
ago and have only just started really using them in anger. I could try 
reproducing it on progressively older kernels to see if I can find one 
that works and then bisect from there.
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