linux-kernel - MEDIA: lirc, improper locking

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Date:	Wed, 07 Jul 2010 14:52:58 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	Jarod Wilson <jarod@...hat.com>
CC:	Mauro Carvalho Chehab <mchehab@...hat.com>,
	linux-media@...r.kernel.org,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: MEDIA: lirc, improper locking

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
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