drm/mediatek: Add cnt checking for coverity issue

[ Upstream commit d761b9450e31e5abd212f0085d424ed32760de5a ]

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.

Fixes: 1ef7ed48356c ("drm/mediatek: Modify mediatek-drm for mt8195 multi mmsys support")
Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20230714094908.13087-3-jason-jh.lin@mediatek.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index 6dcb4ba2466c0d07d01925694a6f34ca8d88632c..fc217e0acd45de2d35c5481c4b74e47d83c33019 100644 (file)
--- 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) {