linux-kernel - Re: BUG: unable to handle kernel NULL pointer dereference in ipv6_select

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Message-ID: <4EF2568C.6040006@bootc.net>
Date:	Wed, 21 Dec 2011 21:58:36 +0000
From:	Chris Boot <bootc@...tc.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	lkml <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: BUG: unable to handle kernel NULL pointer dereference in ipv6_select_ident

On 21/12/2011 20:52, Eric Dumazet wrote:
> Le mercredi 21 décembre 2011 à 21:28 +0100, Eric Dumazet a écrit :
>> Le mercredi 21 décembre 2011 à 20:05 +0000, Chris Boot a écrit :
>>> On 21/12/2011 18:00, Eric Dumazet wrote:
>>>> Le mercredi 21 décembre 2011 à 18:36 +0100, Eric Dumazet a écrit :
>>>>
>>>>> Good point, thats a different problem then, since 3.1 is not supposed to
>>>>> have this bug.
>>>>>
>>>>> It seems rt->rt6i_peer points to invalid memory in your crash.
>>>>>
>>>>> (RBX=00000000000001f4)
>>>>>
>>>>> 8b 83 a4 00 00 00       mov    0xa4(%rbx),%eax    p->refcnt
>>>>> 1f4+a4 ->   CR2=0000000000000298
>>>>>
>>>> It would help if you can confirm latest linux tree can reproduce the
>>>> bug.
>>> Hi Eric,
>>>
>>> I just built a v3.2-rc6-140-gb9e26df with the same config as the Debian
>>> 3.1.0 kernel. I can reproduce the bug just as easily with this kernel as
>>> with the Debian kernel. Unfortunately I wasn't able to get an entire
>>> trace, for some reason it didn't appear to be printed to the serial port
>>> and hung after the (long) list of loaded kernel modules. The crash
>>> happens at the same offset:
>>>
>> Thanks !
>>
>> Oh well, br_netfilter fake_rtable strikes again.
>>
>> I'll cook a patch in a couple of minutes...
>>
> Could you try following patch ?
>
> [snip]

Eric,

It looks good! The rsync that caused the crash real quick hasn't done it 
at all with the patch applied. I'll keep testing it of course, but I 
think that's done it.

Many thanks indeed!

Chris

-- 
Chris Boot
bootc@...tc.net

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