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Date: Wed, 07 Jul 2010 14:52:58 +0200
From: Jiri Slaby <jirislaby@gmail.com>
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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
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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