Re: [PATCH v2] drm/meson: fix potential NULL pointer exception in meson_drv_unbind()
Hello,
first of all: thanks for your patch and sorry for being late with my
review question.
On Fri, Jun 18, 2021 at 7:28 AM Jiajun Cao wrote:
>
> Fix a potential NULL pointer exception when meson_drv_unbind()
> attempts to operate on the driver_data priv which may be NULL.
> Add a null pointer check on the priv struct to avoid the NULL
> pointer dereference after calling dev_get_drvdata(), just like
> the null pointer checks done on the struct priv in the function
> meson_drv_shutdown(), meson_drv_pm_suspend() and meson_drv_pm_resume().
I am trying to review Amlogic Meson related patches in the DRM
subsystem so I can help Neil with this.
However, I am still new to this so please help me educate on this topic.
[...]
> static void meson_drv_unbind(struct device *dev)
> {
> struct meson_drm *priv = dev_get_drvdata(dev);
> - struct drm_device *drm = priv->drm;
> + struct drm_device *drm;
> +
> + if (!priv)
> + return;
My understanding of the component framework is that meson_drv_unbind()
is only called if previously meson_drv_bind() was called (and did not
return any error).
This is different from meson_drv_shutdown() (for example) because that
can be called if meson_drv_probe() returns 0 (success) in case the
"count" variable was 0 (then the probe function does nothing).
As I mentioned before: I am still learning about the DRM subsystem in
the Linux kernel.
So it would be great if you could help me understand for which
scenarios this newly added if-condition is needed.
Thank you!
Best regards,
Martin
[PATCH v2] drm/meson: fix potential NULL pointer exception in meson_drv_unbind()
Fix a potential NULL pointer exception when meson_drv_unbind()
attempts to operate on the driver_data priv which may be NULL.
Add a null pointer check on the priv struct to avoid the NULL
pointer dereference after calling dev_get_drvdata(), just like
the null pointer checks done on the struct priv in the function
meson_drv_shutdown(), meson_drv_pm_suspend() and meson_drv_pm_resume().
Signed-off-by: Jiajun Cao
Signed-off-by: Xin Tan
---
drivers/gpu/drm/meson/meson_drv.c | 6 +-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/meson/meson_drv.c
b/drivers/gpu/drm/meson/meson_drv.c
index 07fcd12dca16..f544fba8c44e 100644
--- a/drivers/gpu/drm/meson/meson_drv.c
+++ b/drivers/gpu/drm/meson/meson_drv.c
@@ -380,7 +380,10 @@ static int meson_drv_bind(struct device *dev)
static void meson_drv_unbind(struct device *dev)
{
struct meson_drm *priv = dev_get_drvdata(dev);
- struct drm_device *drm = priv->drm;
+ struct drm_device *drm;
+
+ if (!priv)
+ return;
if (priv->canvas) {
meson_canvas_free(priv->canvas, priv->canvas_id_osd1);
@@ -389,6 +392,7 @@ static void meson_drv_unbind(struct device *dev)
meson_canvas_free(priv->canvas, priv->canvas_id_vd1_2);
}
+ drm = priv->drm;
drm_dev_unregister(drm);
drm_kms_helper_poll_fini(drm);
drm_atomic_helper_shutdown(drm);
--
2.17.1
