drm: check for minor master before allowing drop master.
When fast user switching a lot eventually we get to the point,
where we were checking for the wrong thing in this function.
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index 1b3e0ff..ef87861 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -185,6 +185,9 @@
if (!file_priv->is_master)
return -EINVAL;
+ if (!file_priv->minor->master)
+ return -EINVAL;
+
mutex_lock(&dev->struct_mutex);
drm_master_put(&file_priv->minor->master);
file_priv->is_master = 0;