On Sun, Nov 11, 2018 at 08:17:40AM -0800, Greg Kroah-Hartman wrote:
>
> The patch below does not apply to the 4.9-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
This one also depends on
36156f9241cb ("of: add helper to lookup compatible child node")
Johan
> ------------------ original commit in Linus's tree ------------------
>
> From ceff2f4dcd44abf35864d9a99f85ac619e89a01d Mon Sep 17 00:00:00 2001
> From: Johan Hovold <johan@xxxxxxxxxx>
> Date: Mon, 27 Aug 2018 10:21:46 +0200
> Subject: [PATCH] drm/mediatek: fix OF sibling-node lookup
>
> Use the new of_get_compatible_child() helper to lookup the sibling
> instead of using of_find_compatible_node(), which searches the entire
> tree from a given start node 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: 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>
> Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
>
> 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",
> cec_np);
> + of_node_put(cec_np);
> return -EPROBE_DEFER;
> }
> + of_node_put(cec_np);
> hdmi->cec_dev = &cec_pdev->dev;
>
> /*
>
