netdev - Re: [regression] nf_iterate(), BUG: unable to handle kernel NULL pointer dereference

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Message-ID: <Pine.LNX.4.64.0807241944450.1907@bizon.gios.gov.pl>
Date:	Thu, 24 Jul 2008 20:00:26 +0200 (CEST)
From:	Krzysztof Oledzki <ole@....pl>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Patrick McHardy <kaber@...sh.net>,
	David Miller <davem@...emloft.net>,
	herbert@...dor.apana.org.au, w@....eu, davidn@...idnewall.com,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	stefanr@...6.in-berlin.de, rjw@...k.pl, ilpo.jarvinen@...sinki.fi,
	Dave Jones <davej@...hat.com>
Subject: Re: [regression] nf_iterate(), BUG: unable to handle kernel NULL
 pointer dereference



On Thu, 24 Jul 2008, Ingo Molnar wrote:

>
> * Patrick McHardy <kaber@...sh.net> wrote:
>
>> Ingo Molnar wrote:
>>> Then i tried both suggested fix patches Patrick sent me (a suggested
>>> revert and an netfilter/RCU use-after-free fix), but none of them
>>> solved the crash.
>>
>> Just to make sure - the "netfilter/RCU use-after-free fix" was the
>> patch from Pekka?
>
> yes. You can see it in tip/out-of-tree:
>
>   http://people.redhat.com/mingo/tip.git/README
>
>>> Thus i finally arrived to:
>>>
>>>  # good: [ae6134bd] hdlcdrv: Fix CRC calculation.
>>>  # bad:  [5547cd0d] netfilter: nf_conntrack_sctp: fix sparse warnings
>>>  # bad:  [280763c6] netfilter: xt_time: fix time's time_mt()'s use of
>>>  # good: [07a7c10b] netlink: add NLA_PUT_BE64 macro
>>>  # bad:  [58401573] netfilter: accounting rework: ct_extend + 64bit co
>>>
>>> | 584015727a3b88b46602b20077b46cd04f8b4ab3 is first bad commit
>>> | commit 584015727a3b88b46602b20077b46cd04f8b4ab3
>>> | Author: Krzysztof Piotr Oledzki <ole@....pl>
>>> | AuthorDate: Mon Jul 21 10:01:34 2008 -0700
>>> | Commit:     David S. Miller <davem@...emloft.net>
>>> | CommitDate: Mon Jul 21 10:10:58 2008 -0700
>>> |
>>> |    netfilter: accounting rework: ct_extend + 64bit counters (v4)
>>> [...]
>>> |     Signed-off-by: Krzysztof Piotr Oledzki <ole@....pl>
>>> |     Signed-off-by: Patrick McHardy <kaber@...sh.net>
>>> |     Signed-off-by: David S. Miller <davem@...emloft.net>
>>>
>>> Which i double-checked by reverting that commit from -git as well and
>>> that solved the crash. Find the tested reverter patch below.
>>
>> Thats odd. I don't think anything is wrong with that patch itself, its
>> more likely that its triggering a bug in ct_extend. You config has a
>> few helper enabled (FTP, H.323, TFTP) and the crash is when trying to
>> call the helper functions. Did you actually have traffic of one of
>> these protocols?
>
> no, that's not likely - it's a default distro bootup.

The commit makes ct_extend area to be used *very* frequently. Could you 
try to boot your kernel with nf_conntrack.acct=0 to disable accounting?
Does it help?

Best regards,

 				Krzysztof Olędzki