linux-kernel - Re: 2.6.24-rc6-mm1 - git-lblnet.patch and networking horkage

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Message-ID: <Xine.LNX.4.64.0801010841060.25768@us.intercode.com.au>
Date:	Tue, 1 Jan 2008 08:46:09 +1100 (EST)
From:	James Morris <jmorris@...ei.org>
To:	Paul Moore <paul.moore@...com>
cc:	Valdis.Kletnieks@...edu, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, sds@...ho.nsa.gov,
	netdev@...r.kernel.org
Subject: Re: 2.6.24-rc6-mm1 - git-lblnet.patch and networking horkage

On Mon, 31 Dec 2007, Paul Moore wrote:

> I'm pretty certain this is an uninitialized value problem now and not a 
> use-after-free issue.  The invalid/garbage ->iif value seems to only happen 
> on packets that are generated locally and sent back into the stack for local 
> consumption, e.g. loopback.  These local packets also need to have been 
> cloned at some point, either on the output or input path.

I think we need to find out exactly what's happening, first.

> The problem appears to be a skb_clone() function which does not clear the skb 
> structure properly and fails to copy the ->iif value from the original skb to 
> the cloned skb.  From what I can tell, there are two possible solutions to 
> this problem:
> 
>  1. Clear all of the cloned skb fields in skb_clone() via memset()

Sounds like it's not going to fly for performance reasons in any case.

>  2. Copy the ->iif field in __copy_skb_header()

Seems valid.


- James
-- 
James Morris
<jmorris@...ei.org>
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