[PATCH] drm/mediatek: Initialize pointer before use to avoid undefiend behaviour

[CK Hu (胡俊光)]

Hi, Karan:

On Mon, 2024-11-11 at 18:14 +0000, Karan Sanghavi wrote:
> External email : Please do not click links or open attachments until you have verified the sender or the content.
> 
> 
> Initialize the pointer with NULL as mtk_drm_of_get_ddp_ep_cid
> function might return before assigning value to next pointer
> but yet further dereference to next can lead to some undefined
> behavior as it may point to some invalid location.

Reviewed-by: CK Hu <ck.hu at mediatek.com>

> 
> Fixes: 4c932840db1d ("drm/mediatek: Implement OF graphs support for display paths")
> Signed-off-by: Karan Sanghavi <karansanghvi98 at gmail.com>
> ---
> Coverity Message:
> CID 1601557: (#1 of 1): Uninitialized pointer read (UNINIT)
> 3. uninit_use: Using uninitialized value next.
> 
> Coverity Link:
> https://urldefense.com/v3/__https://scan7.scan.coverity.com/*/project-view/10043/11354?selectedIssue=1601557__;Iw!!CTRNKA9wMg0ARbw!hoVl7EQYL36rg2pnVInf2AL6m6mTbIeAsFyOuAlfdlSRMyvrR_vU4CAuIv1h5NnvGEUwMsEY8qxDQ8Mgkc5JyTo$
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index 9a8ef8558da9..bc06c664e80f 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -900,7 +900,7 @@ static int mtk_drm_of_ddp_path_build_one(struct device *dev, enum mtk_crtc_path
>                                          const unsigned int **out_path,
>                                          unsigned int *out_path_len)
>  {
> -       struct device_node *next, *prev, *vdo = dev->parent->of_node;
> +       struct device_node *next = NULL, *prev, *vdo = dev->parent->of_node;
>         unsigned int temp_path[DDP_COMPONENT_DRM_ID_MAX] = { 0 };
>         unsigned int *final_ddp_path;
>         unsigned short int idx = 0;
> 
> ---
> base-commit: 6d59cab07b8d74d0f0422b750038123334f6ecc2
> change-id: 20241111-uninitializedpointer1601557-9803b725b6bd
> 
> Best regards,
> --
> Karan Sanghavi <karansanghvi98 at gmail.com>
>