[PATCH 1/2] drm/amdgpu: protect potential NULL pointer dereferencing

[Alex Deucher]

On Tue, Aug 26, 2025 at 3:38 PM David (Ming Qiang) Wu <David.Wu3 at amd.com> wrote:
>
> to_amdgpu_userq_fence() could return NULL which should be
> protected.

Same thing here.  The amdgpu_userq_fence is a container for the dma_fence.

Alex

>
> Signed-off-by: David (Ming Qiang) Wu <David.Wu3 at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
> index a86616c6deeff..01d30544c30d1 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
> @@ -297,15 +297,18 @@ static const char *amdgpu_userq_fence_get_timeline_name(struct dma_fence *f)
>  {
>         struct amdgpu_userq_fence *fence = to_amdgpu_userq_fence(f);
>
> -       return fence->fence_drv->timeline_name;
> +       return fence ? fence->fence_drv->timeline_name : "";
>  }
>
>  static bool amdgpu_userq_fence_signaled(struct dma_fence *f)
>  {
>         struct amdgpu_userq_fence *fence = to_amdgpu_userq_fence(f);
> -       struct amdgpu_userq_fence_driver *fence_drv = fence->fence_drv;
> +       struct amdgpu_userq_fence_driver *fence_drv;
>         u64 rptr, wptr;
>
> +       if (!fence)
> +               return false;
> +       fence_drv = fence->fence_drv;
>         rptr = amdgpu_userq_fence_read(fence_drv);
>         wptr = fence->base.seqno;
>
> @@ -319,8 +322,11 @@ static void amdgpu_userq_fence_free(struct rcu_head *rcu)
>  {
>         struct dma_fence *fence = container_of(rcu, struct dma_fence, rcu);
>         struct amdgpu_userq_fence *userq_fence = to_amdgpu_userq_fence(fence);
> -       struct amdgpu_userq_fence_driver *fence_drv = userq_fence->fence_drv;
> +       struct amdgpu_userq_fence_driver *fence_drv;
>
> +       if (!userq_fence)
> +               return;
> +       fence_drv = userq_fence->fence_drv;
>         /* Release the fence driver reference */
>         amdgpu_userq_fence_driver_put(fence_drv);
>
> --
> 2.43.0
>