[PATCH 2/9] drm/mediatek: fix OF sibling-node lookup

From: Johan Hovold
Date: Wed Aug 22 2018 - 06:57:23 EST

Use the new of_get_compatible_child() helper to lookup the sibling
instead of using of_find_compatible_node(), which searches the entire
tree and thus can return an unrelated (i.e. non-sibling) node.

This also addresses a potential use-after-free (e.g. after probe
deferral) as the tree-wide helper drops a reference to its first
argument (i.e. the parent device node).

While at it, also fix the related cec-node reference leak.

Fixes: 8f83f26891e1 ("drm/mediatek: Add HDMI support")
Cc: stable <stable@xxxxxxxxxxxxxxx> # 4.8
Cc: Jie Qiu <jie.qiu@xxxxxxxxxxxx>
Cc: Junzhi Zhao <junzhi.zhao@xxxxxxxxxxxx>
Cc: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
Cc: CK Hu <ck.hu@xxxxxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
drivers/gpu/drm/mediatek/mtk_hdmi.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c b/drivers/gpu/drm/mediatek/mtk_hdmi.c
index 2d45d1dd9554..643f5edd68fe 100644
--- a/drivers/gpu/drm/mediatek/mtk_hdmi.c
+++ b/drivers/gpu/drm/mediatek/mtk_hdmi.c
@@ -1446,8 +1446,7 @@ static int mtk_hdmi_dt_parse_pdata(struct mtk_hdmi *hdmi,

/* The CEC module handles HDMI hotplug detection */
- cec_np = of_find_compatible_node(np->parent, NULL,
- "mediatek,mt8173-cec");
+ cec_np = of_get_compatible_child(np->parent, "mediatek,mt8173-cec");
if (!cec_np) {
dev_err(dev, "Failed to find CEC node\n");
return -EINVAL;
@@ -1457,8 +1456,10 @@ static int mtk_hdmi_dt_parse_pdata(struct mtk_hdmi *hdmi,
if (!cec_pdev) {
dev_err(hdmi->dev, "Waiting for CEC device %pOF\n",
+ of_node_put(cec_np);
+ of_node_put(cec_np);
hdmi->cec_dev = &cec_pdev->dev;