linux-kernel - Re: [Stable-review] [07/55] SUNRPC: Fix a race between work-queue and rpc_killall

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Date:	Mon, 8 Aug 2011 19:07:35 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Greg KH <gregkh@...e.de>
Cc:	linux-kernel@...r.kernel.org, stable@...nel.org,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	stable-review@...nel.org, alan@...rguk.ukuu.org.uk
Subject: Re: [Stable-review] [07/55] SUNRPC: Fix a race between work-queue
 and rpc_killall_tasks

On Mon, Aug 08, 2011 at 10:03:00AM -0700, Greg KH wrote:
> On Sun, Aug 07, 2011 at 06:38:01PM +0100, Ben Hutchings wrote:
> > On Fri, 2011-08-05 at 17:01 -0700, Greg KH wrote:
> > > 2.6.32-longterm review patch.  If anyone has any objections, please let us know.
> > > 
> > > ------------------
> > > 
> > > From: Trond Myklebust <Trond.Myklebust@...app.com>
> > > 
> > > commit b55c59892e1f3b6c7d4b9ccffb4263e1486fb990 upstream.
> > > 
> > > Since rpc_killall_tasks may modify the rpc_task's tk_action field
> > > without any locking, we need to be careful when dereferencing it.
> > [...]
> > 
> > This isn't nearly careful enough to avoid races.  You must at least use
> > the ACCESS_ONCE macro, otherwise the compiler can just optimise away the
> > local variable this introduces.
> 
> Well, that's an upstream issue as well, right?  Not much I can do here
> in the stable updates :)
 
Right, but if it doesn't fix a bug then it is not suitable for
stable.

Ben.

-- 
Ben Hutchings
We get into the habit of living before acquiring the habit of thinking.
                                                              - Albert Camus
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