netdev - Re: [PATCH net-next-2.6] l2tp: fix potential rcu race

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Message-Id: <20110512.172741.1724338998672360298.davem@davemloft.net>
Date:	Thu, 12 May 2011 17:27:41 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	paulmck@...ux.vnet.ibm.com
Cc:	eric.dumazet@...il.com, netdev@...r.kernel.org,
	jchapman@...alix.com
Subject: Re: [PATCH net-next-2.6] l2tp: fix potential rcu race

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Date: Thu, 12 May 2011 07:26:41 -0700

> On Thu, May 12, 2011 at 06:22:36AM +0200, Eric Dumazet wrote:
>> While trying to remove useless synchronize_rcu() calls, I found l2tp is
>> indeed incorrectly using two of such calls, but also bumps tunnel
>> refcount after list insertion.
>> 
>> tunnel refcount must be incremented before being made publically visible
>> by rcu readers.
>> 
>> This fix can be applied to 2.6.35+ and might need a backport for older
>> kernels, since things were shuffled in commit fd558d186df2c
>> (l2tp: Split pppol2tp patch into separate l2tp and ppp parts)
> 
> Ouch!  Good catch, Eric!
> 
> Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

Applied, thanks Eric.
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