Date: Sun, 22 Jun 2008 10:58:32 -0700
From: Arjan van de Ven <arjan@infradead.org>
To: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: mchehab@infradead.org, linux-kernel@vger.kernel.org,
       Al Viro <viro@ftp.linux.org.uk>
Subject: Re: [PATCH] Fix open/close race in saa7134
Message-ID: <20080622105832.1c61fb92@infradead.org>
In-Reply-To: <20080622172826.GA7487@joi>
References: <20080622100507.779acc59@infradead.org>
	<20080622172826.GA7487@joi>
Organization: Intel
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1483
Lines: 36

On Sun, 22 Jun 2008 19:33:37 +0200
Marcin Slusarz <marcin.slusarz@gmail.com> wrote:

> On Sun, Jun 22, 2008 at 10:05:07AM -0700, Arjan van de Ven wrote:
> > 
> > From: Arjan van de Ven <arjan@linux.intel.com>
> > Date: Sun, 22 Jun 2008 10:03:02 -0700
> > Subject: [PATCH] Fix open/close race in saa7134
> > 
> > The saa7134 driver uses a (non-atomic) variable in an attempt to
> > only allow one opener of the device (how it deals with sending
> > the fd over unix sockets I don't know).
> > 
> > Unfortunately, the release function first decrements this variable,
> > and THEN goes on to disable more of the device. This allows for
> > a race where another opener of the device comes in after the
> > decrement of the variable, configures the hardware just to then see
> > the hardware be disabled by the rest of the release function.
> 
> Simplier fix:
> http://lkml.org/lkml/2008/6/9/308
> But I don't remember whether it was applied or not...


the patch might be simpler, but it's not fully correct...
the decrement is non-atomic and not protected by any lock whatsoever.

-- 
If you want to reach me at my work email, use arjan@linux.intel.com
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/