[PATCH AUTOSEL 5.3 05/87] drm/kms: Catch mode_object lifetime errors

Sasha Levin
2019-09-24T16:42:00Z

From: Daniel Vetter <daniel.vetter@ffwll.ch>

[ Upstream commit 4f5368b5541a902f6596558b05f5c21a9770dd32 ]

Only dynamic mode objects, i.e. those which are refcounted and have a free
callback, can be added while the overall drm_device is visible to
userspace. All others must be added before drm_dev_register and
removed after drm_dev_unregister.

Small issue around drivers still using the load/unload callbacks, we
need to make sure we set dev->registered so that load/unload code in
these callbacks doesn't trigger false warnings. Only a small
adjustement in drm_dev_register was needed.

Motivated by some irc discussions about object ids of dynamic objects
like blobs become invalid, and me going on a bit an audit spree.

Reviewed-by: Sean Paul <sean@poorly.run>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190614061723.1173-1-daniel.vetter@ffwll.ch
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/drm_drv.c | 4 ++--
drivers/gpu/drm/drm_mode_object.c | 4 ++++
2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 9d00947ca447f..e652305d8f98a 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -978,14 +978,14 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
if (ret)
goto err_minors;

- dev->registered = true;
-
if (dev->driver->load) {
ret = dev->driver->load(dev, flags);
if (ret)
goto err_minors;
}

+ dev->registered = true;
+
if (drm_core_check_feature(dev, DRIVER_MODESET))
drm_modeset_register_all(dev);

diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/drm_mode_object.c
index 1c6e511359624..c355ba8e6d5dd 100644
--- a/drivers/gpu/drm/drm_mode_object.c
+++ b/drivers/gpu/drm/drm_mode_object.c
@@ -42,6 +42,8 @@ int __drm_mode_object_add(struct drm_device *dev, struct drm_mode_object *obj,
{
int ret;

+ WARN_ON(dev->registered && !obj_free_cb);
+
mutex_lock(&dev->mode_config.idr_mutex);
ret = idr_alloc(&dev->mode_config.object_idr, register_obj ? obj : NULL,
1, 0, GFP_KERNEL);
@@ -102,6 +104,8 @@ void drm_mode_object_register(struct drm_device *dev,
void drm_mode_object_unregister(struct drm_device *dev,
struct drm_mode_object *object)
{
+ WARN_ON(dev->registered && !object->free_cb);
+
mutex_lock(&dev->mode_config.idr_mutex);
if (object->id) {
idr_remove(&dev->mode_config.object_idr, object->id);
--
2.20.1