netdev - Re: Bug in net/ipv6/ip6_fib.c:fib6_dump

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Message-ID: <1340310469.4604.6702.camel@edumazet-glaptop>
Date:	Thu, 21 Jun 2012 22:27:49 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Josh Hunt <johunt@...mai.com>
Cc:	"davem@...emloft.net" <davem@...emloft.net>,
	"kaber@...sh.net" <kaber@...sh.net>,
	Debabrata Banerjee <dbavatar@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"yoshfuji@...ux-ipv6.org" <yoshfuji@...ux-ipv6.org>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"pekkas@...core.fi" <pekkas@...core.fi>,
	"kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Bug in net/ipv6/ip6_fib.c:fib6_dump_table()

On Thu, 2012-06-21 at 14:35 -0500, Josh Hunt wrote:

> Can anyone provide details of the crash which was intended to be fixed
> by 2bec5a369ee79576a3eea2c23863325089785a2c? With this patch in and
> doing concurrent adds/deletes and dumping the table via netlink causes
> duplicate entries to be reported. Reverting this patch causes those
> problems to go away. We can provide a more detailed test if that is
> needed, but so far our testing has been unable to reproduce the crash
> mentioned in the above commit with it reverted.

A mere revert wont be enough.

Looking at this code, it lacks proper synchronization
between tree updaters and tree walkers.

fib6_walker_lock rwlock is not enough to prevent races.

Are you willing to fix this yourself ?



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