Re: [PATCH v2 1/6] drm: msm: remove resv fields from msm_gem_object struct

[Bjorn Andersson]

On Wed 08 May 19:03 PDT 2019, Brian Masney wrote:

> The msm_gem_object structure contains resv and _resv fields that are
> no longer needed since the reservation object is now stored on
> drm_gem_object. msm_atomic_prepare_fb() and msm_atomic_prepare_fb()
> both referenced the wrong reservation object, and would lead to an
> attempt to dereference a NULL pointer. Correct those two cases to
> point to the correct reservation object.
> 
> Signed-off-by: Brian Masney <masneyb@xxxxxxxxxxxxx>
> Fixes: dd55cf6929e6 ("drm: msm: Switch to use drm_gem_object reservation_object")

Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
Tested-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>

This resolves a NULL-pointer dereference about to show up in v5.2-rc1,
so please pick this up for -rc.

Regards,
Bjorn

> ---
> Patch introduced in v2
> 
>  drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c | 4 +---
>  drivers/gpu/drm/msm/msm_atomic.c          | 4 +---
>  drivers/gpu/drm/msm/msm_gem.c             | 3 ---
>  drivers/gpu/drm/msm/msm_gem.h             | 4 ----
>  4 files changed, 2 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> index da1f727d7495..ce1a555e1f31 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> @@ -780,7 +780,6 @@ static int dpu_plane_prepare_fb(struct drm_plane *plane,
>  	struct dpu_plane_state *pstate = to_dpu_plane_state(new_state);
>  	struct dpu_hw_fmt_layout layout;
>  	struct drm_gem_object *obj;
> -	struct msm_gem_object *msm_obj;
>  	struct dma_fence *fence;
>  	struct dpu_kms *kms = _dpu_plane_get_kms(&pdpu->base);
>  	int ret;
> @@ -799,8 +798,7 @@ static int dpu_plane_prepare_fb(struct drm_plane *plane,
>  	 *       implicit fence and fb prepare by hand here.
>  	 */
>  	obj = msm_framebuffer_bo(new_state->fb, 0);
> -	msm_obj = to_msm_bo(obj);
> -	fence = reservation_object_get_excl_rcu(msm_obj->resv);
> +	fence = reservation_object_get_excl_rcu(obj->resv);
>  	if (fence)
>  		drm_atomic_set_fence_for_plane(new_state, fence);
>  
> diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c
> index f5b1256e32b6..131c23a267ee 100644
> --- a/drivers/gpu/drm/msm/msm_atomic.c
> +++ b/drivers/gpu/drm/msm/msm_atomic.c
> @@ -49,15 +49,13 @@ int msm_atomic_prepare_fb(struct drm_plane *plane,
>  	struct msm_drm_private *priv = plane->dev->dev_private;
>  	struct msm_kms *kms = priv->kms;
>  	struct drm_gem_object *obj;
> -	struct msm_gem_object *msm_obj;
>  	struct dma_fence *fence;
>  
>  	if (!new_state->fb)
>  		return 0;
>  
>  	obj = msm_framebuffer_bo(new_state->fb, 0);
> -	msm_obj = to_msm_bo(obj);
> -	fence = reservation_object_get_excl_rcu(msm_obj->resv);
> +	fence = reservation_object_get_excl_rcu(obj->resv);
>  
>  	drm_atomic_set_fence_for_plane(new_state, fence);
>  
> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
> index 31d5a744d84f..947508e8269d 100644
> --- a/drivers/gpu/drm/msm/msm_gem.c
> +++ b/drivers/gpu/drm/msm/msm_gem.c
> @@ -973,9 +973,6 @@ static int msm_gem_new_impl(struct drm_device *dev,
>  	msm_obj->flags = flags;
>  	msm_obj->madv = MSM_MADV_WILLNEED;
>  
> -	if (resv)
> -		msm_obj->base.resv = resv;
> -
>  	INIT_LIST_HEAD(&msm_obj->submit_entry);
>  	INIT_LIST_HEAD(&msm_obj->vmas);
>  
> diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
> index c5ac781dffee..812d1b1369a5 100644
> --- a/drivers/gpu/drm/msm/msm_gem.h
> +++ b/drivers/gpu/drm/msm/msm_gem.h
> @@ -86,10 +86,6 @@ struct msm_gem_object {
>  
>  	struct llist_node freed;
>  
> -	/* normally (resv == &_resv) except for imported bo's */
> -	struct reservation_object *resv;
> -	struct reservation_object _resv;
> -
>  	/* For physically contiguous buffers.  Used when we don't have
>  	 * an IOMMU.  Also used for stolen/splashscreen buffer.
>  	 */
> -- 
> 2.20.1
>