[PATCH 1/2] drm/amdgpu: fix use after free during BO move

[Das, Nirmoy]

  Acked-by: Nirmoy Das <nirmoy.das at amd.com> for the 1st patch and second 
patch is

Reviewed-by: Nirmoy Das <nirmoy.das at amd.com>


On 9/7/2021 10:14 AM, Christian König wrote:
> The memory backing old_mem is already freed at that point, move the
> check a bit more up.
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> Fixes: bfa3357ef9ab ("drm/ttm: allocate resource object instead of embedding it v2")
> Bug: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Fdrm%2Famd%2F-%2Fissues%2F1699&data=04%7C01%7Cnirmoy.das%40amd.com%7Ce76c4a0ac29e480fcf7108d971d79344%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637665992971099794%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=JttDenpA2ZII0Ttktn3HMVodWWU0kJoPVPvQ3%2BnN4sw%3D&reserved=0
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 18 +++++++++---------
>   1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 446943e32e3e..e2896ac2c9ce 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -513,6 +513,15 @@ static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
>   		goto out;
>   	}
>   
> +	if (bo->type == ttm_bo_type_device &&
> +	    new_mem->mem_type == TTM_PL_VRAM &&
> +	    old_mem->mem_type != TTM_PL_VRAM) {
> +		/* amdgpu_bo_fault_reserve_notify will re-set this if the CPU
> +		 * accesses the BO after it's moved.
> +		 */
> +		abo->flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED;
> +	}
> +
>   	if (adev->mman.buffer_funcs_enabled) {
>   		if (((old_mem->mem_type == TTM_PL_SYSTEM &&
>   		      new_mem->mem_type == TTM_PL_VRAM) ||
> @@ -543,15 +552,6 @@ static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
>   			return r;
>   	}
>   
> -	if (bo->type == ttm_bo_type_device &&
> -	    new_mem->mem_type == TTM_PL_VRAM &&
> -	    old_mem->mem_type != TTM_PL_VRAM) {
> -		/* amdgpu_bo_fault_reserve_notify will re-set this if the CPU
> -		 * accesses the BO after it's moved.
> -		 */
> -		abo->flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED;
> -	}
> -
>   out:
>   	/* update statistics */
>   	atomic64_add(bo->base.size, &adev->num_bytes_moved);