Re: [PATCH v3] drm/ttm: Avoid NULL pointer deref for evicted BOs

[Matthew Brost <matthew.brost@intel.com>]

On Tue, Oct 14, 2025 at 01:11:33AM +0900, Simon Richter wrote:
> It is possible for a BO to exist that is not currently associated with a
> resource, e.g. because it has been evicted.
> 
> When devcoredump tries to read the contents of all BOs for dumping, we need
> to expect this as well -- in this case, ENODATA is recorded instead of the
> buffer contents.
> 
> Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6271

I think we need a fixes / cc stable but I can add that for you when merging.

Anyways patch LGTM:
Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> Signed-off-by: Simon Richter <Simon.Richter@hogyros.de>
> ---
>  drivers/gpu/drm/ttm/ttm_bo_vm.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index b47020fca199..a101ff95b234 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -434,6 +434,11 @@ int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
>  	if (ret)
>  		return ret;
>  
> +	if (!bo->resource) {
> +		ret = -ENODATA;
> +		goto unlock;
> +	}
> +
>  	switch (bo->resource->mem_type) {
>  	case TTM_PL_SYSTEM:
>  		fallthrough;
> @@ -448,6 +453,7 @@ int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
>  			ret = -EIO;
>  	}
>  
> +unlock:
>  	ttm_bo_unreserve(bo);
>  
>  	return ret;
> -- 
> 2.47.3
>