Messages in this thread | | | Subject | Re: [PATCH] drm: Fix possible race conditions while unplugging DRM device | From | Oleksandr Andrushchenko <> | Date | Tue, 29 May 2018 10:09:57 +0300 |
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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 > -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
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