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

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Date:	Thu, 24 Jul 2008 17:32:48 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	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>,
	Krzysztof Piotr Oledzki <ole@....pl>
Subject: Re: [regression] nf_iterate(), BUG: unable to handle kernel NULL
	pointer dereference


* 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.

	Ingo
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