netdev - Re: [Bugme-new] [Bug 8057] New: slab corruption running ip6sic

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Date:	Mon, 23 Apr 2007 08:44:16 +0200
From:	Jarek Poplawski <jarkao2@...pl>
To:	David Miller <davem@...emloft.net>
Cc:	akpm@...ux-foundation.org, netdev@...r.kernel.org,
	bugme-daemon@...zilla.kernel.org, snakebyte@....de
Subject: Re: [Bugme-new] [Bug 8057] New: slab corruption running ip6sic

On Fri, Apr 20, 2007 at 04:35:15PM -0700, David Miller wrote:
> From: Jarek Poplawski <jarkao2@...pl>
> Date: Mon, 12 Mar 2007 11:24:03 +0100
> 
> > > the ipcomp handler is xfrm6_rcv(), which calls xfrm6_rcv_spi(), which contrary
> > > to all other handlers returns -1 instead of 0 after calling kfree_skb() on the
> > > skb. Changing the return value to 0 in xfrm6_input.c:xfrm6_rcv_spi() fixes the
> > > problem.
> > > But I got no clue at all if this would be a correct fix
> > 
> > I think your diagnose is correct (all "return -1" should be
> > changed to "return 0" in xfrm6_input.c).

I've corrected this, yet:

"Sorry! Of course should be:
I think your diagnose is correct (all "return -1" should be
changed to "return 0" in xfrm6_rcv_spi())."

It's just like Eric diagnosed:

xfrm6_rcv() calls tunnel6_rcv(), which calls handlers->handler()
and if handler() returns anything but 0, skb is kfreed. But
handler: xfrm6_tunnel_rcv() calls xfrm6_rcv_spi() and returns its
return without changing, which is only 1 and -1. It seems, in
every -1 case skb is kfreed by xfrm6_rcv_spi() or by functions
called by it, probably meaning skb was handled (delivered or
kfreed). The only path where skb is not kfreed returns 1.

tunnel6_rcv() treats both returns the same way - so some skbs
are kfreed 2 times.

Regards,
Jarek P.
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