From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754567AbeE2GZO (ORCPT ); Tue, 29 May 2018 02:25:14 -0400 Received: from mail-wr0-f193.google.com ([209.85.128.193]:36680 "EHLO mail-wr0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751668AbeE2GZM (ORCPT ); Tue, 29 May 2018 02:25:12 -0400 X-Google-Smtp-Source: ADUXVKLw3H2fZQadDVE5jpA7JjJud61ZeNTLpDaXzcRCaPDNUhD9PIn17CJQVpfkgQucWKuNGNM6pA== Subject: Re: [PATCH] drm: Fix possible race conditions while unplugging DRM device To: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, airlied@linux.ie, daniel.vetter@intel.com, seanpaul@chromium.org, gustavo@padovan.org Cc: Oleksandr Andrushchenko , =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= References: <20180522141304.18646-1-andr2000@gmail.com> From: Oleksandr Andrushchenko Message-ID: <226cb967-2464-767b-c051-95c120f6558a@gmail.com> Date: Tue, 29 May 2018 09:25:09 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180522141304.18646-1-andr2000@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ping On 05/22/2018 05:13 PM, 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" > --- > 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); >