lkml.org 
[lkml]   [2018]   [May]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] drm: Fix possible race conditions while unplugging DRM device
From
Date
On 05/29/2018 10:49 AM, Daniel Vetter wrote:
> 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 <oleksandr_andrushchenko@epam.com>
>>>>
>>>> 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 <oleksandr_andrushchenko@epam.com>
>>>> Reported-by: Andrii Chepurnyi <andrii_chepurnyi@epam.com>
>>>> Cc: "Noralf Trønnes" <noralf@tronnes.org>
>>> Nice catch.
>>>
>>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>>>
>>> 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
>
Applied to drm-misc-next-fixes
>>> -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

\
 
 \ /
  Last update: 2018-05-31 09:49    [W:0.050 / U:0.628 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site