Re: FAILED: patch "[PATCH] drm/msm: fix OF child-node lookup" failed to apply to 4.14-stable tree

[Johan Hovold <johan@kernel.org>]

On Thu, Nov 29, 2018 at 09:06:29AM +0100, Greg Kroah-Hartman wrote:
> On Tue, Nov 27, 2018 at 07:19:38AM -0800, Johan Hovold wrote:
> > On Mon, Nov 19, 2018 at 03:07:37PM +0100, 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")
> 
> No, still does not apply to 4.14 even with that patch :(

Looks like the function in question was moved by commit 999ae6edc1c1
("drm/msm/adreno: Move clock parsing to adreno_gpu_init()").

Compile-tested backport below.

Johan


>From 8ac9a34ac02928bcc2975fd3da39671fd4d533e7 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Mon, 27 Aug 2018 10:21:47 +0200
Subject: [PATCH] drm/msm: fix OF child-node lookup

commit f9a7082327e26f54067a49cac2316d31e0cc8ba7 upstream.

Use the new of_get_compatible_child() helper to lookup the legacy
pwrlevels child node 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-child) 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 probed device's node).

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

Fixes: e2af8b6b0ca1 ("drm/msm: gpu: Use OPP tables if we can")
Cc: stable <stable@vger.kernel.org>     # 4.12
Cc: Jordan Crouse <jcrouse@codeaurora.org>
Cc: Rob Clark <robdclark@gmail.com>
Cc: David Airlie <airlied@linux.ie>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
[ johan: backport to 4.14 ]
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/gpu/drm/msm/adreno/adreno_device.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c b/drivers/gpu/drm/msm/adreno/adreno_device.c
index c75c4df4bc39..2c379774d3f2 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_device.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
@@ -223,8 +223,7 @@ static int adreno_get_legacy_pwrlevels(struct device *dev)
 	struct device_node *child, *node;
 	int ret;
 
-	node = of_find_compatible_node(dev->of_node, NULL,
-		"qcom,gpu-pwrlevels");
+	node = of_get_compatible_child(dev->of_node, "qcom,gpu-pwrlevels");
 	if (!node) {
 		dev_err(dev, "Could not find the GPU powerlevels\n");
 		return -ENXIO;
@@ -245,6 +244,8 @@ static int adreno_get_legacy_pwrlevels(struct device *dev)
 			dev_pm_opp_add(dev, val, 0);
 	}
 
+	of_node_put(node);
+
 	return 0;
 }
 
-- 
2.19.2