linux-kernel - Re: MEDIA: lirc, improper locking

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Date:	Wed, 7 Jul 2010 10:00:35 -0400
From:	Jarod Wilson <jarod@...hat.com>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	Mauro Carvalho Chehab <mchehab@...hat.com>,
	linux-media@...r.kernel.org,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: MEDIA: lirc, improper locking

On Wed, Jul 07, 2010 at 02:52:58PM +0200, Jiri Slaby wrote:
> Hi,
> 
> stanse found a locking error in lirc_dev_fop_read:
> if (mutex_lock_interruptible(&ir->irctl_lock))
>   return -ERESTARTSYS;
> ...
> while (written < length && ret == 0) {
>   if (mutex_lock_interruptible(&ir->irctl_lock)) {    #1
>     ret = -ERESTARTSYS;
>     break;
>   }
>   ...
> }
> 
> remove_wait_queue(&ir->buf->wait_poll, &wait);
> set_current_state(TASK_RUNNING);
> mutex_unlock(&ir->irctl_lock);                        #2
> 
> If lock at #1 fails, it beaks out of the loop, with the lock unlocked,
> but there is another "unlock" at #2.

Yeah, ok, I see the problem there, should be able to get a patch to fix it
in flight later today.

Thanks much,

-- 
Jarod Wilson
jarod@...hat.com

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