From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932236AbeE2Htj (ORCPT ); Tue, 29 May 2018 03:49:39 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:56103 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932081AbeE2Hth (ORCPT ); Tue, 29 May 2018 03:49:37 -0400 X-Google-Smtp-Source: AB8JxZoAjvmnHwUU0FgnZXDnLFgmh9v311O6cIOw95symUAkEJ2oxar1/zjgMO5gsxcBL6ofMvvbZA== Date: Tue, 29 May 2018 09:49:33 +0200 From: Daniel Vetter To: Oleksandr Andrushchenko Cc: "Oleksandr_Andrushchenko@epam.com" , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, airlied@linux.ie, daniel.vetter@intel.com, seanpaul@chromium.org, gustavo@padovan.org, Noralf =?iso-8859-1?Q?Tr=F8nnes?= Subject: Re: [PATCH] drm: Fix possible race conditions while unplugging DRM device Message-ID: <20180529074933.GY3438@phenom.ffwll.local> Mail-Followup-To: Oleksandr Andrushchenko , "Oleksandr_Andrushchenko@epam.com" , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, airlied@linux.ie, daniel.vetter@intel.com, seanpaul@chromium.org, gustavo@padovan.org, Noralf =?iso-8859-1?Q?Tr=F8nnes?= References: <20180522141304.18646-1-andr2000@gmail.com> <20180529070200.GW3438@phenom.ffwll.local> <3427121e-ddd9-d2ba-b684-61338f0207ce@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3427121e-ddd9-d2ba-b684-61338f0207ce@gmail.com> X-Operating-System: Linux phenom 4.15.0-3-amd64 User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 29, 2018 at 10:09:57AM +0300, Oleksandr Andrushchenko wrote: > On 05/29/2018 10:02 AM, Daniel Vetter wrote: > > On Tue, May 22, 2018 at 05:13:04PM +0300, Oleksandr Andrushchenko wrote: > > > From: Oleksandr Andrushchenko > > > > > > When unplugging a hotpluggable DRM device we first unregister it > > > with drm_dev_unregister and then set drm_device.unplugged flag which > > > is used to mark device critical sections with drm_dev_enter()/ > > > drm_dev_exit() preventing access to device resources that are not > > > available after the device is gone. > > > But drm_dev_unregister may lead to hotplug uevent(s) fired to > > > user-space on card and/or connector removal, thus making it possible > > > for user-space to try accessing a disconnected device. > > > > > > Fix this by first making sure device is properly marked as > > > disconnected and only then unregister it. > > > > > > Fixes: bee330f3d672 ("drm: Use srcu to protect drm_device.unplugged") > > > > > > Signed-off-by: Oleksandr Andrushchenko > > > Reported-by: Andrii Chepurnyi > > > Cc: "Noralf Trønnes" > > Nice catch. > > > > Reviewed-by: Daniel Vetter > > > > I think you need to push this to drm-misc-next-fixes to make sure it's on > > the 4.17 train. > Sure, after I have r-b from Noralf Noralf's occasionally occupied with other things and doesn't have time to look at patches. I think it's ok to just push after a few more days, even if he doesn't respond. Same holds for other people really. -Daniel > > -Daniel > > > > > --- > > > drivers/gpu/drm/drm_drv.c | 14 +++++++------- > > > 1 file changed, 7 insertions(+), 7 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c > > > index b553a6f2ff0e..7af748ed1c58 100644 > > > --- a/drivers/gpu/drm/drm_drv.c > > > +++ b/drivers/gpu/drm/drm_drv.c > > > @@ -369,13 +369,6 @@ EXPORT_SYMBOL(drm_dev_exit); > > > */ > > > void drm_dev_unplug(struct drm_device *dev) > > > { > > > - drm_dev_unregister(dev); > > > - > > > - mutex_lock(&drm_global_mutex); > > > - if (dev->open_count == 0) > > > - drm_dev_put(dev); > > > - mutex_unlock(&drm_global_mutex); > > > - > > > /* > > > * After synchronizing any critical read section is guaranteed to see > > > * the new value of ->unplugged, and any critical section which might > > > @@ -384,6 +377,13 @@ void drm_dev_unplug(struct drm_device *dev) > > > */ > > > dev->unplugged = true; > > > synchronize_srcu(&drm_unplug_srcu); > > > + > > > + drm_dev_unregister(dev); > > > + > > > + mutex_lock(&drm_global_mutex); > > > + if (dev->open_count == 0) > > > + drm_dev_put(dev); > > > + mutex_unlock(&drm_global_mutex); > > > } > > > EXPORT_SYMBOL(drm_dev_unplug); > > > -- > > > 2.17.0 > > > > > > _______________________________________________ > > > dri-devel mailing list > > > dri-devel@lists.freedesktop.org > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch