netdev - Re: Multitude of dst obsolescense race conditions

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Message-Id: <1400074523.15916.117311749.3590532D@webmail.messagingengine.com>
Date:	Wed, 14 May 2014 06:35:23 -0700
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	dormando <dormando@...ia.net>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: Multitude of dst obsolescense race conditions

On Wed, May 14, 2014, at 2:57, dormando wrote:
> Given a machine with frequently changing routes (ie; a router with an
> active internet BGP table and multiple interfaces), there're at least
> several places where obsolete dst's are handled improperly. If I pause
> the
> route changes, the crashes appear to stop. This first one has a crash
> utility we've made, so I was able to more quickly find a patch and test
> it. The others take time to reproduce.
> 
> I'm testing against 3.10.39, but I think if these were fixed they'd be
> backported to stable? I've also had recent 3.12's running that have
> crashed in the same spots. Anyway correct me if I'm wrong...

Just a hunch:
You use macvlan? Could you somehow try without?
Maybe... some ref overflow? (You could add some testing code in dst_hold
with atomic_inc_return and WARN_ON).

dst_release already contains such a check, so I am not sure at all if
that could happen.

Bye,

  Hannes
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