Message-ID: <1415638955.9613.4.camel@edumazet-glaptop2.roam.corp.google.com>
Subject: Re: [Xen-devel] BUG in xennet_make_frags with paged skb data
From: Eric Dumazet <eric.dumazet@gmail.com>
To: David Vrabel <david.vrabel@citrix.com>
Cc: Zoltan Kiss <zoltan.kiss@linaro.org>, netdev@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Stefan Bader <stefan.bader@canonical.com>,
        Jay Vosburgh <jay.vosburgh@canonical.com>,
        linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org
Date: Mon, 10 Nov 2014 09:02:35 -0800
In-Reply-To: <5460EAF1.5020903@citrix.com>
References: <20141106214940.GD44162@ubuntu-hedt>
	 <545CA27F.4070400@citrix.com>	<20141110143517.GA74005@ubuntu-hedt>
	 <5460CEA5.3070201@citrix.com> <5460EA45.2080202@linaro.org>
	 <5460EAF1.5020903@citrix.com>
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Sender: linux-kernel-owner@vger.kernel.org

On Mon, 2014-11-10 at 16:42 +0000, David Vrabel wrote:
> On 10/11/14 16:39, Zoltan Kiss wrote:
> > 
> > The BUG_ON suggested by Stefan would be still reasonable:
> > 
> > BUG_ON(((page-compound_head(page))*PAGE_SIZE)+offset+len >
> > PAGE_SIZE<<compound_order(compound_head(page)));
> 
> Well, it wouldn't trigger but I don't think it is useful any more.

Right.

This BUG_ON() does not make sense (its current implementation is
assuming a very precise layout anyway)

If we really wanted some debugging, we would need something more generic
and done in core networking stack, not in a particular driver.


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