netdev - Re: [PATCH 3.2-3.12] skbuff: skb_segment: orphan frags before copying

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Date:	Mon, 14 Apr 2014 00:50:10 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	David Miller <davem@...emloft.net>
Cc:	stable@...r.kernel.org, mst@...hat.com,
	herbert@...dor.apana.org.au, netdev@...r.kernel.org
Subject: Re: [PATCH 3.2-3.12] skbuff: skb_segment: orphan frags before
 copying

On Sun, 2014-04-13 at 19:20 -0400, David Miller wrote:
> From: Ben Hutchings <ben@...adent.org.uk>
> Date: Sun, 13 Apr 2014 23:57:40 +0100
> 
> > From: "Michael S. Tsirkin" <mst@...hat.com>
> > 
> > commit 1fd819ecb90cc9b822cd84d3056ddba315d3340f upstream.
> > 
> > skb_segment copies frags around, so we need
> > to copy them carefully to avoid accessing
> > user memory after reporting completion to userspace
> > through a callback.
> > 
> > skb_segment doesn't normally happen on datapath:
> > TSO needs to be disabled - so disabling zero copy
> > in this case does not look like a big deal.
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> > Acked-by: Herbert Xu <herbert@...dor.apana.org.au>
> > Signed-off-by: David S. Miller <davem@...emloft.net>
> > [bwh: Backported to 3.2.  As skb_segment() only supports page-frags *or* a
> >  frag list, there is no need for the additional frag_skb pointer or the
> >  preparatory renaming.]
> > Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
> > ---
> > For branches older than 3.6, commit a353e0ce0fd4 ('skbuff: add an api to
> > orphan frags') is needed before this.  This is untested and I would
> > appreciate a review.
> 
> I didn't do this backport because it seemed risky unless Michael
> or someone else tested it thoroughly.

Understood; I'll wait for further feedback.

Ben.

-- 
Ben Hutchings
I say we take off; nuke the site from orbit.  It's the only way to be sure.

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