netdev - Re: [PATCH] fix NULL pointer + success return in route lookup path

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Message-Id: <20090620.011543.74198631.davem@davemloft.net>
Date:	Sat, 20 Jun 2009 01:15:43 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	nhorman@...driver.com
Cc:	netdev@...r.kernel.org, mbizon@...ebox.fr, dada1@...mosbay.com,
	kuznet@....inr.ac.ru, pekkas@...core.fi, jmorris@...ei.org,
	yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH] fix NULL pointer + success return in route lookup path

From: Neil Horman <nhorman@...driver.com>
Date: Fri, 19 Jun 2009 13:18:14 -0400

> Don't drop route if we're not caching	
> 
> 	I recently got a report of an oops on a route lookup.  Maxime was
> testing what would happen if route caching was turned off (doing so by setting
> making rt_caching always return 0), and found that it triggered an oops.  I
> looked at it and found that the problem stemmed from the fact that the route
> lookup routines were returning success from their lookup paths (which is good),
> but never set the **rp pointer to anything (which is bad).  This happens because
> in rt_intern_hash, if rt_caching returns false, we call rt_drop and return 0.
> This almost emulates slient success.  What we should be doing is assigning *rp =
> rt and _not_ dropping the route.  This way, during slow path lookups, when we
> create a new route cache entry, we don't immediately discard it, rather we just
> don't add it into the cache hash table, but we let this one lookup use it for
> the purpose of this route request.  Maxime has tested and reports it prevents
> the oops.  There is still a subsequent routing issue that I'm looking into
> further, but I'm confident that, even if its related to this same path, this
> patch makes sense to take.
> 
> Signed-off-by: Neil Horman <nhorman@...driver.com>

Applied and queued up for -stable, thanks.
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