[PATCH v4 2/4] drm/mediatek: Add cnt checking for coverity issue

[Jason-JH.Lin]

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 at mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
Reviewed-by: CK Hu <ck.hu at mediatek.com>
Reviewed-by: Alexandre Mergnat <amergnat at baylibre.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) {
-- 
2.18.0