From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Date: Tue, 22 May 2018 17:13:04 +0300
Subject: drm: Fix possible race conditions while unplugging DRM device
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Git-commit: 069035c5db3459b9b5f12caf3bffed9a863fa5c4
Patch-mainline: v4.18-rc2
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166
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
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/gpu/drm/drm_drv.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
--- 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 *d
*/
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);