From 069035c5db3459b9b5f12caf3bffed9a863fa5c4 Mon Sep 17 00:00:00 2001 From: Oleksandr Andrushchenko Date: Tue, 22 May 2018 17:13:04 +0300 Subject: drm: Fix possible race conditions while unplugging DRM device MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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" Reviewed-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20180522141304.18646-1-andr2000@gmail.com --- 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 f6910ebe4d0e..cc2675550e28 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); -- cgit v1.2.3