netdev - Re: [bug] __nf_ct_refresh_acct(): WARNING: at lib/list_debug.c:30 __list

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4A38EFC4.8000907@trash.net>
Date:	Wed, 17 Jun 2009 15:29:40 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>, David Miller <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [bug] __nf_ct_refresh_acct(): WARNING: at lib/list_debug.c:30
 __list_add+0x7d/0xad()

Eric Dumazet wrote:
> Patrick McHardy a écrit :
>> Eric Dumazet wrote:
>>> Patrick McHardy a écrit :
>>>> Eric Dumazet wrote:
>>>>> Patrick McHardy a écrit :
>>>>>> Before the conntrack is confirmed, it is exclusively handled by a
>>>>>> single CPU. I agree that we need to make sure the IPS_CONFIRMED_BIT
>>>>>> is visible before we add the conntrack to the hash table since the
>>>>>> lookup is lockless, but simply moving the set_bit before the hash
>>>>>> insertion should be fine I think.
>>>>>>
>>>>> Problem is timeout.expires is either a relative or absolute timeout,
>>>>> and changes happen
>>>>> in __nf_conntrack_confirm() or __nf_ct_refresh_acct().
>>>>>
>>>>> We must have a synchronization (an barriers), a single bit wont be
>>>>> enough.
>>>> Please have a look at the second patch I just sent. It relies
>>>> on the RCU barriers to make sure all stores are visible before
>>>> other CPUs can find the conntrack.
>>>>
>>> Sorry, I dont understand how your second patch corrects the problem.
>>>
>>> This (unconfirmed) conntrack is visible by another cpu.
>> No, before it is confirmed, its only visible to the CPU handling
>> the initial packet of a connection. Confirmation is the step that
>> makes it visible to other CPUs.
> 
> Thanks Patrick, I missed this, and your patch seems fine now :)

Thanks for your help, I'll send it to Dave later today.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html