Re: [Intel-gfx] [PATCH] drm/i915: Fix possible null ptr dereferences

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Dec 03, 2021 at 12:02:57PM +0530, Pallavi Mishra wrote:
> add null ptr checks to prevent crash/exceptions.

BUG_ON()s aren't going to fix anything.

> Signed-off-by: Pallavi Mishra <pallavi.mishra@intel.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_ttm.c      | 3 +++
>  drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c | 3 ++-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> index 218a9b3037c7..997fe73c205b 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> @@ -906,6 +906,8 @@ vm_access_ttm(struct vm_area_struct *area, unsigned long addr,
>  	struct drm_i915_gem_object *obj =
>  		i915_ttm_to_gem(area->vm_private_data);
>  
> +	GEM_BUG_ON(!obj);
> +
>  	if (i915_gem_object_is_readonly(obj) && write)
>  		return -EACCES;
>  
> @@ -966,6 +968,7 @@ static const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = {
>  void i915_ttm_bo_destroy(struct ttm_buffer_object *bo)
>  {
>  	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
> +	GEM_BUG_ON(!obj);
>  
>  	i915_gem_object_release_memory_region(obj);
>  	mutex_destroy(&obj->ttm.get_io_page.lock);
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
> index 80df9f592407..2b684903a9f5 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
> @@ -371,6 +371,7 @@ int i915_ttm_move_notify(struct ttm_buffer_object *bo)
>  	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
>  	int ret;
>  
> +	GEM_BUG_ON(!obj);
>  	ret = i915_gem_object_unbind(obj, I915_GEM_OBJECT_UNBIND_ACTIVE);
>  	if (ret)
>  		return ret;
> @@ -506,7 +507,7 @@ static void i915_ttm_memcpy_init(struct i915_ttm_memcpy_arg *arg,
>  
>  	dst_reg = i915_ttm_region(bo->bdev, dst_mem->mem_type);
>  	src_reg = i915_ttm_region(bo->bdev, bo->resource->mem_type);
> -	GEM_BUG_ON(!dst_reg || !src_reg);
> +	GEM_BUG_ON(!dst_reg || !src_reg || !obj);
>  
>  	arg->dst_iter = !i915_ttm_cpu_maps_iomem(dst_mem) ?
>  		ttm_kmap_iter_tt_init(&arg->_dst_iter.tt, dst_ttm) :
> -- 
> 2.25.1

-- 
Ville Syrjälä
Intel