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

From: Ingo Molnar <[email-masked]>
Date: Thu, 24 Jul 2008 17:32:48 +0200

* Patrick McHardy <[email-masked]> 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 <[email-masked]>
>> | AuthorDate: Mon Jul 21 10:01:34 2008 -0700
>> | Commit:     David S. Miller <[email-masked]>
>> | CommitDate: Mon Jul 21 10:10:58 2008 -0700
>> |
>> |    netfilter: accounting rework: ct_extend + 64bit counters (v4)
>> [...]
>> |     Signed-off-by: Krzysztof Piotr Oledzki <[email-masked]>
>> |     Signed-off-by: Patrick McHardy <[email-masked]>
>> |     Signed-off-by: David S. Miller <[email-masked]>
>>
>> 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