linux-kernel - Re: [PATCH v2 2/4] drm/mediatek: Add cnt checking for coverity issue

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Message-ID: <7d125255-513b-c5e7-3b9c-57131deab49c@collabora.com>
Date:   Wed, 14 Jun 2023 10:43:01 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     "Jason-JH.Lin" <jason-jh.lin@...iatek.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Alexandre Mergnat <amergnat@...libre.com>
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        Rex-BC Chen <rex-bc.chen@...iatek.com>,
        Jason-ch Chen <jason-ch.chen@...iatek.com>,
        Johnson Wang <johnson.wang@...iatek.com>,
        Singo Chang <singo.chang@...iatek.com>,
        Nancy Lin <nancy.lin@...iatek.com>,
        Shawn Sung <shawn.sung@...iatek.com>,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v2 2/4] drm/mediatek: Add cnt checking for coverity issue

Il 13/06/23 13:32, Jason-JH.Lin ha scritto:
> 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.
> 
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> Fixes: 1ef7ed48356c ("drm/mediatek: Modify mediatek-drm for mt8195 multi mmsys support")

Fixes tag goes before your S-o-b tag.

Anyway,
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

> ---
>   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) {