Re: FAILED: patch "[PATCH] drm/mediatek: fix OF sibling-node lookup" failed to apply to 4.9-stable tree

[Johan Hovold <johan@kernel.org>]

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@vger.kernel.org>.

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@kernel.org>
> 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@vger.kernel.org>     # 4.8
> Cc: Junzhi Zhao <junzhi.zhao@mediatek.com>
> Cc: Philipp Zabel <p.zabel@pengutronix.de>
> Cc: CK Hu <ck.hu@mediatek.com>
> Cc: David Airlie <airlied@linux.ie>
> Signed-off-by: Johan Hovold <johan@kernel.org>
> Signed-off-by: Rob Herring <robh@kernel.org>
> 
> 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;
>  
>  	/*
>