netdev - Re: Possible netfilter-related memory corruption in 2.6.37

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Date:	Mon, 14 Feb 2011 17:24:37 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Jan Engelhardt <jengelh@...ozas.de>, Avi Kivity <avi@...hat.com>,
	netfilter-devel@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	nicolas prochazka <prochazka.nicolas@...il.com>,
	KVM list <kvm@...r.kernel.org>, netdev <netdev@...r.kernel.org>
Subject: Re: Possible netfilter-related memory corruption in 2.6.37

Am 14.02.2011 16:50, schrieb Eric Dumazet:
> Le lundi 14 février 2011 à 16:18 +0100, Jan Engelhardt a écrit :
>> On Monday 2011-02-14 16:11, Eric Dumazet wrote:
>>
>>> Le lundi 14 février 2011 à 16:58 +0200, Avi Kivity a écrit :
>>>> We see severe memory corruption in kvm while used in conjunction with 
>>>> bridge/netfilter.  Enabling slab debugging points the finger at a 
>>>> netfilter chain invoked from the bridge code.
>>>>
>>>> Can someone take a look?
>>>>
>>>> https://bugzilla.kernel.org/show_bug.cgi?id=27052
>>
>> Maybe looks familiar to https://lkml.org/lkml/2011/2/3/147
> 
> Are you sure Jan ?
> 
> IMHO it looks like in your case, a NULL ->hook() is called, from
> nf_iterate()
> 
> BTW, list_for_each_continue_rcu() really should be converted to 
> list_for_each_entry_continue_rcu()
> 
> This is a bit ugly :
> 
> list_for_each_continue_rcu(*i, head) {
> 	struct nf_hook_ops *elem = (struct nf_hook_ops *)*i;
> 
> Also, I wonder if RCU rules are respected in nf_iterate().
> For example this line is really suspicious :
> 
> *i = (*i)->prev;

Yeah, that definitely looks wrong. How about this instead?


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