[PATCH] drm/amdgpu: avoid NULL pointer dereference

[Das, Nirmoy]

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

On 12/22/2021 3:19 PM, Guchun Chen wrote:
> amdgpu_umc_poison_handler for UMC RAS consumption gets
> called in KFD queue reset, but it needs to return early when
> RAS context is NULL. This can guarantee lower access to
> RAS context like in amdgpu_umc_do_page_retirement. Also
> improve coding style in amdgpu_umc_poison_handler.
>
> Signed-off-by: Guchun Chen <guchun.chen at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_umc.c | 12 ++++++++----
>   1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_umc.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_umc.c
> index 46264a4002f7..b455fc7d1546 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_umc.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_umc.c
> @@ -112,16 +112,20 @@ int amdgpu_umc_poison_handler(struct amdgpu_device *adev,
>   		void *ras_error_status,
>   		bool reset)
>   {
> -	int ret;
>   	struct ras_err_data *err_data = (struct ras_err_data *)ras_error_status;
>   	struct ras_common_if head = {
>   		.block = AMDGPU_RAS_BLOCK__UMC,
>   	};
> -	struct ras_manager *obj = amdgpu_ras_find_obj(adev, &head);
> +	struct amdgpu_ras *con = amdgpu_ras_get_context(adev);
> +	struct ras_manager *obj;
> +	int ret;
> +
> +	if (!con)
> +		return 0;
>   
> -	ret =
> -		amdgpu_umc_do_page_retirement(adev, ras_error_status, NULL, reset);
> +	ret = amdgpu_umc_do_page_retirement(adev, ras_error_status, NULL, reset);
>   
> +	obj = amdgpu_ras_find_obj(adev, &head);
>   	if (ret == AMDGPU_RAS_SUCCESS && obj) {
>   		obj->err_data.ue_count += err_data->ue_count;
>   		obj->err_data.ce_count += err_data->ce_count;