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

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Message-ID: <1297698641.2996.38.camel@edumazet-laptop>
Date:	Mon, 14 Feb 2011 16:50:41 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jan Engelhardt <jengelh@...ozas.de>
Cc:	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

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;



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