From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <shemminger@osdl.org>
Subject: Re: [TCP]: Fix truesize underflow
Date: Wed, 19 Apr 2006 09:53:48 -0700
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References: <20060418123204.GA3962@gondor.apana.org.au>
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Cc: "Boris B. Zhmurov" <bb@kernelpanic.ru>,
	Phil Oester <kernel@linuxace.com>,
	Mark Nipper <nipsy@bitgnome.net>,
	"David S. Miller" <davem@davemloft.net>,
	jesse.brandeburg@intel.com, jrlundgren@gmail.com, cat@zip.com.au,
	djani22@dynamicweb.hu, yoseph.basri@gmail.com, mykleb@no.ibm.com,
	olel@ans.pl, michal@feix.cz, chris@scorpion.nl,
	netdev@vger.kernel.org, jesse.brandeburg@gmail.com,
	Andi Kleen <ak@suse.de>, Jeff Garzik <jgarzik@pobox.com>
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To: Herbert Xu <herbert@gondor.apana.org.au>
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On Tue, 18 Apr 2006 22:32:04 +1000
Herbert Xu <herbert@gondor.apana.org.au> wrote:

> Hi Dave:
> 
> You're absolutely right about there being a problem with the TSO packet
> trimming code.  The cause of this lies in the tcp_fragment() function.
> 
> When we allocate a fragment for a completely non-linear packet the
> truesize is calculated for a payload length of zero.  This means that
> truesize could in fact be less than the real payload length.
> 
> When that happens the TSO packet trimming can cause truesize to become
> negative.  This in turn can cause sk_forward_alloc to be -n * PAGE_SIZE
> which would trigger the warning.
> 
> I've copied the code you used in tso_fragment which should work here.
> 
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> 
> Everyone who's having the sk_forward_alloc warning problem should give
> this patch a go to see if it cures things.
> 
> Just in case this still doesn't fix it, could everyone please also verify
> whether disabling SMP has any effect on reproducing this?
> 
> Thanks,

Please put this in the next -stable load...