Messages in this thread | | | Subject | Re: [PATCH] drm: Fix possible race conditions while unplugging DRM device | From | Oleksandr Andrushchenko <> | Date | Tue, 29 May 2018 09:25:09 +0300 |
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On 05/22/2018 05:13 PM, 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> > --- > 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); >
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