[PATCH 2/7] drm/meson: fix possible object reference leak

[PATCH 2/7] drm/meson: fix possible object reference leak

[Wen Yang]

The call to of_graph_get_remote_port returns a node pointer with refcount
incremented thus it must be explicitly decremented after the last
usage.

Detected by coccinelle with the following warnings:
drivers/gpu/drm/meson/meson_dw_hdmi.c:725:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 722, but without a corresponding object release within this function.

Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-amlogic@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org (open list)
---
 drivers/gpu/drm/meson/meson_dw_hdmi.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c
index 563953e..109a933 100644
--- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
+++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
@@ -720,13 +720,10 @@ static bool meson_hdmi_connector_is_available(struct device *dev)
 
 	/* If the endpoint node exists, consider it enabled */
 	remote = of_graph_get_remote_port(ep);
-	if (remote) {
-		of_node_put(ep);
-		return true;
-	}
-
 	of_node_put(ep);
 	of_node_put(remote);
+	if (remote)
+		return true;
 
 	return false;
 }
-- 
2.9.5


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Re: [PATCH 2/7] drm/meson: fix possible object reference leak

[Markus Elfring]

> @@ -720,13 +720,10 @@ static bool meson_hdmi_connector_is_available(struct device *dev)
>
>  	/* If the endpoint node exists, consider it enabled */
>  	remote = of_graph_get_remote_port(ep);
> -	if (remote) {
> -		of_node_put(ep);
> -		return true;
> -	}
> -
>  	of_node_put(ep);
>  	of_node_put(remote);

https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/gpu/drm/meson/meson_dw_hdmi.c?id=61de49cb596710b918f7a80839f0b6de2017bc32#n712

Can the order of these put calls matter (because of processor caches)?


> +	if (remote)
> +		return true;
>
>  	return false;

Would the use of a ternary operator be more succinct here?

+	return remote ? true : false;

Regards,
Markus

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