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authorOleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>2018-05-22 17:13:04 +0300
committerOleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>2018-05-31 10:36:28 +0300
commit069035c5db3459b9b5f12caf3bffed9a863fa5c4 (patch)
treef32b505ef20d1e6dba33220a5681fd71b330344d
parentfbecef131676c1d18e8e6b42c04e10dc49725e96 (diff)
drm: Fix possible race conditions while unplugging DRM devicedrm-misc-next-fixes-2018-06-15
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> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20180522141304.18646-1-andr2000@gmail.com
-rw-r--r--drivers/gpu/drm/drm_drv.c14
1 files 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);