Re: [PATCH v3 2/4] drm/mediatek: Add cnt checking for coverity issue
From: CK Hu (胡俊光)
Date: Mon Jul 10 2023 - 02:46:05 EST
Hi, Jason:
On Wed, 2023-06-21 at 18:22 +0800, Jason-JH.Lin wrote:
> CERT-C Characters and Strings (CERT STR31-C)
> all_drm_priv[cnt] evaluates to an address that could be at negative
> offset of an array.
>
> In mtk_drm_get_all_drm_priv():
> Guarantee that storage for strings has sufficient space for character
> data and the null terminator.
>
> So change cnt to unsigned int and check its max value.
Reviewed-by: CK Hu <ck.hu@xxxxxxxxxxxx>
>
> Fixes: 1ef7ed48356c ("drm/mediatek: Modify mediatek-drm for mt8195
> multi mmsys support")
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@xxxxxxxxxxxx>
> Reviewed-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/mediatek/mtk_drm_drv.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index 6dcb4ba2466c..fc217e0acd45 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -354,7 +354,7 @@ static bool mtk_drm_get_all_drm_priv(struct
> device *dev)
> const struct of_device_id *of_id;
> struct device_node *node;
> struct device *drm_dev;
> - int cnt = 0;
> + unsigned int cnt = 0;
> int i, j;
>
> for_each_child_of_node(phandle->parent, node) {
> @@ -375,6 +375,9 @@ static bool mtk_drm_get_all_drm_priv(struct
> device *dev)
> all_drm_priv[cnt] = dev_get_drvdata(drm_dev);
> if (all_drm_priv[cnt] && all_drm_priv[cnt]-
> >mtk_drm_bound)
> cnt++;
> +
> + if (cnt == MAX_CRTC)
> + break;
> }
>
> if (drm_priv->data->mmsys_dev_num == cnt) {