On Sun, Nov 11, 2018 at 08:18:36AM -0800, Greg Kroah-Hartman wrote:

The patch below does not apply to the 4.14-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;

/*