Return-path: <linux-media-owner@vger.kernel.org>
Received: from mail-bw0-f46.google.com ([209.85.214.46]:48069 "EHLO
	mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1754920Ab0GGMxO (ORCPT
	<rfc822;linux-media@vger.kernel.org>); Wed, 7 Jul 2010 08:53:14 -0400
Message-ID: <4C3478AA.7070805@gmail.com>
Date: Wed, 07 Jul 2010 14:52:58 +0200
From: Jiri Slaby <jirislaby@gmail.com>
MIME-Version: 1.0
To: Jarod Wilson <jarod@redhat.com>
CC: Mauro Carvalho Chehab <mchehab@redhat.com>,
	linux-media@vger.kernel.org,
	Linux kernel mailing list <linux-kernel@vger.kernel.org>
Subject: MEDIA: lirc, improper locking
Content-Type: text/plain; charset=ISO-8859-2
Content-Transfer-Encoding: 7bit
Sender: linux-media-owner@vger.kernel.org
List-ID: <linux-media.vger.kernel.org>

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.

regards,
-- 
js