Re: [bug report] drm/ttm: Add a generic TTM memcpy move for page-based iomem

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

Hello Dan Carpenter.

Thanks for the report.

On 4/13/22 13:11, Dan Carpenter wrote:
> Hello Thomas Hellström,
>
> The patch 3bf3710e3718: "drm/ttm: Add a generic TTM memcpy move for
> page-based iomem" from Jun 2, 2021, leads to the following Smatch
> static checker warning:
>
> 	./include/drm/ttm/ttm_bo_driver.h:259 ttm_bo_move_sync_cleanup()
> 	error: NULL dereference inside function 'ttm_bo_move_accel_cleanup()'
>
> ./include/drm/ttm/ttm_bo_driver.h
>      256 static inline void ttm_bo_move_sync_cleanup(struct ttm_buffer_object *bo,
>      257                                             struct ttm_resource *new_mem)
>      258 {
> --> 259         int ret = ttm_bo_move_accel_cleanup(bo, NULL, true, false, new_mem);
>                                                          ^^^^
> Passing a NULL for "fence" will crash.  The first place where it will
> crash is in dma_resv_add_fence() where it does:

Indeed, and this has been discussed thoroughly on dri-devel lately. The 
bug was introduced in a recent patch that made NULL pointers here crash. 
Not the patch indicated.

Thanks,

Thomas



>
> 	WARN_ON(dma_fence_is_container(fence));
>
>      260
>      261         WARN_ON(ret);
>      262 }
>
> regards,
> dan carpenter