[PATCH] drm/mediatek: Fix return type of mtk_hdmi_bridge_mode_valid()

[Chun-Kuang Hu]

 Hi, Nathan:

Nathan Chancellor <nathan at kernel.org> 於 2022年11月2日 週三 晚上11:47寫道：
>
> With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
> indirect call targets are validated against the expected function
> pointer prototype to make sure the call target is valid to help mitigate
> ROP attacks. If they are not identical, there is a failure at run time,
> which manifests as either a kernel panic or thread getting killed. A
> proposed warning in clang aims to catch these at compile time, which
> reveals:
>
>   drivers/gpu/drm/mediatek/mtk_hdmi.c:1407:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_bridge *, const struct drm_display_info *, const struct drm_display_mode *)' with an expression of type 'int (struct drm_bridge *, const struct drm_display_info *, const struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict]
>           .mode_valid = mtk_hdmi_bridge_mode_valid,
>                         ^~~~~~~~~~~~~~~~~~~~~~~~~~
>   1 error generated.
>
> ->mode_valid() in 'struct drm_bridge_funcs' expects a return type of
> 'enum drm_mode_status', not 'int'. Adjust the return type of
> mtk_hdmi_bridge_mode_valid() to match the prototype's to resolve the
> warning and CFI failure.

Applied to mediatek-drm-next [1], thanks.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/log/?h=mediatek-drm-next

Chun-Kuang.

>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1750
> Reported-by: Sami Tolvanen <samitolvanen at google.com>
> Signed-off-by: Nathan Chancellor <nathan at kernel.org>
> ---
>  drivers/gpu/drm/mediatek/mtk_hdmi.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c b/drivers/gpu/drm/mediatek/mtk_hdmi.c
> index 4c80b6896dc3..6e8f99554f54 100644
> --- a/drivers/gpu/drm/mediatek/mtk_hdmi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_hdmi.c
> @@ -1202,9 +1202,10 @@ static enum drm_connector_status mtk_hdmi_detect(struct mtk_hdmi *hdmi)
>         return mtk_hdmi_update_plugged_status(hdmi);
>  }
>
> -static int mtk_hdmi_bridge_mode_valid(struct drm_bridge *bridge,
> -                                     const struct drm_display_info *info,
> -                                     const struct drm_display_mode *mode)
> +static enum drm_mode_status
> +mtk_hdmi_bridge_mode_valid(struct drm_bridge *bridge,
> +                          const struct drm_display_info *info,
> +                          const struct drm_display_mode *mode)
>  {
>         struct mtk_hdmi *hdmi = hdmi_ctx_from_bridge(bridge);
>         struct drm_bridge *next_bridge;
>
> base-commit: 9abf2313adc1ca1b6180c508c25f22f9395cc780
> --
> 2.38.1
>