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

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

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.

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
> > >