netdev - Re: [PATCH] netfilter: per netns nf_conntrack

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Date:	Tue, 02 Feb 2010 17:48:22 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Jon Masters <jonathan@...masters.org>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	netfilter-devel <netfilter-devel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH] netfilter: per netns nf_conntrack_cachep

Jon Masters wrote:
> On Tue, 2010-02-02 at 06:35 -0500, Jon Masters wrote:
> 
>> I think there's something more fundamental going on here.
> 
> What happens is the conntrack code attempts to free
> nf_conntrack_untracked back into the SL[U]B cache from which it
> allocates other ct's.

That shouldn't happen, the untracked conntrack is initialized to a
refcount of 1, which is never released.

> There's just one problem...that's a static struct
> not from the cache. So, this is why we end up with the SLAB being
> corrupted and the address immediately following the
> nf_conntrack_untracked being corrupted.
> 
> I shoved some debug comments into the destroy code to see if we were
> trying to free nf_conntrack_untracked, and bingo. I have shoved a panic
> in there now, will send you a backtrace.

Thanks.
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