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

["Christian König" <christian.koenig@amd.com>]

On 12/5/25 19:25, Matthew Brost wrote:
> On Fri, Dec 05, 2025 at 10:46:34AM -0700, Lin, Shuicheng wrote:
>> On Mon, Oct 13, 2025 9:27 AM Matthew Brost wrote:
>>> 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>
>>
> 
> Christian - any objection to me pushing this patch drm-misc-next or
> would it be drm-misc-fixes? I forget the flow here.

Good catch! I somehow totally missed that patch.

Reviewed-by: Christian König <christian.koenig@amd.com>

And with the CC stable tag that should go to drm-misc-fixes.

Regards,
Christian.

> 
> Matt 
> 
>> It seems this patch is not merged yet.
>>
>> LGTM.
>> Reviewed-by: Shuicheng Lin <shuicheng.lin@intel.com>
>>
>>>> ---
>>>>  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
>>>>