From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753378AbbFHTZQ (ORCPT ); Mon, 8 Jun 2015 15:25:16 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:60350 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753247AbbFHTZM (ORCPT ); Mon, 8 Jun 2015 15:25:12 -0400 Date: Mon, 8 Jun 2015 12:25:07 -0700 From: Guenter Roeck To: Brian Russell Cc: Greg Kroah-Hartman , Brian Russell , "Hans J. Koch" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v9 2/2] uio: Fix uio driver to refcount device Message-ID: <20150608192507.GA13169@roeck-us.net> References: <550C34B4.6030703@brocade.com> <20150323204145.GA22203@kroah.com> <55115FAA.50800@brocade.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55115FAA.50800@brocade.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: guenter@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 24, 2015 at 12:59:22PM +0000, Brian Russell wrote: > > > On 23/03/15 20:41, Greg Kroah-Hartman wrote: > > On Fri, Mar 20, 2015 at 02:54:44PM +0000, Brian Russell wrote: > >> Protect uio driver from its owner being unplugged while there are open fds. > >> Embed struct device in struct uio_device, use refcounting on device, free > >> uio_device on release. > >> info struct passed in uio_register_device can be freed on unregister, so null > >> out the field in uio_unregister_device and check accesses. > > > > That's really not protecting anything except heavy-handed problems... > > > > Look at the code: > > > >> @@ -493,7 +499,7 @@ static unsigned int uio_poll(struct file *filep, poll_table *wait) > >> struct uio_listener *listener = filep->private_data; > >> struct uio_device *idev = listener->dev; > >> > >> - if (!idev->info->irq) > >> + if (!idev->info || !idev->info->irq) > >> return -EIO; > >> > > > > Great, you checked the irq value, but what if it changes the very next > > line: > > > >> poll_wait(filep, &idev->wait, wait); > > > > Or any other line within this function? Or any other function that you > > try to check the value for in the beginning... > > > > This really isn't protecting anything "properly", sorry. Either we > > don't care about it (hint, I don't think we really do), or we need to > > properly lock things and check, and protect, things that way. > > > > The checks for irq value are already there. I added the checks for the > idev->info ptr and deliberately nulled it in uio_unregister_device as > the caller module may free uio_info after unregistering (dpdk's igb_uio > does anyway) and then release will be called later when fds are closed. > > So I think I definitely need the check in uio_release. I didn't think > it hurt to return early from poll/read/write if we know the device > has been unregistered? > What is the final verdict on this patch ? We are seeing the crash in our system, and I would like to apply a 'final' patch if possible to get it fixed. Thanks, Guenter