[PATCH 1/7] drm/mediatek: fix possible object reference leak

[PATCH 1/7] drm/mediatek: fix possible object reference leak

[Wen Yang]

The call to of_parse_phandle 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/mediatek/mtk_hdmi.c:1521:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 1509, but without a corresponding object release within this function.
drivers/gpu/drm/mediatek/mtk_hdmi.c:1524:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 1509, but without a corresponding object release within this function.

Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: CK Hu <ck.hu@mediatek.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mediatek@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
---
 drivers/gpu/drm/mediatek/mtk_hdmi.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c b/drivers/gpu/drm/mediatek/mtk_hdmi.c
index 915cc84..ed10f4d 100644
--- a/drivers/gpu/drm/mediatek/mtk_hdmi.c
+++ b/drivers/gpu/drm/mediatek/mtk_hdmi.c
@@ -1516,6 +1516,7 @@ static int mtk_hdmi_dt_parse_pdata(struct mtk_hdmi *hdmi,
 	of_node_put(remote);
 
 	hdmi->ddc_adpt = of_find_i2c_adapter_by_node(i2c_np);
+	of_node_put(i2c_np);
 	if (!hdmi->ddc_adpt) {
 		dev_err(dev, "Failed to get ddc i2c adapter by node\n");
 		return -EINVAL;
-- 
2.9.5


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Re: [PATCH 1/7] drm/mediatek: fix possible object reference leak

[CK Hu]

Hi, Wen:

On Thu, 2019-04-04 at 00:04 +0800, Wen Yang wrote:
> The call to of_parse_phandle 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/mediatek/mtk_hdmi.c:1521:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 1509, but without a corresponding object release within this function.
> drivers/gpu/drm/mediatek/mtk_hdmi.c:1524:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 1509, but without a corresponding object release within this function.

For this patch, applied to mediatek-drm-fixes-5.1 [1], thanks.

[1]
https://github.com/ckhu-mediatek/linux.git-tags/commits/mediatek-drm-fixes-5.1

Regards,
CK

> 
> Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
> Cc: CK Hu <ck.hu@mediatek.com>
> Cc: Philipp Zabel <p.zabel@pengutronix.de>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Matthias Brugger <matthias.bgg@gmail.com>
> Cc: dri-devel@lists.freedesktop.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-mediatek@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  drivers/gpu/drm/mediatek/mtk_hdmi.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c b/drivers/gpu/drm/mediatek/mtk_hdmi.c
> index 915cc84..ed10f4d 100644
> --- a/drivers/gpu/drm/mediatek/mtk_hdmi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_hdmi.c
> @@ -1516,6 +1516,7 @@ static int mtk_hdmi_dt_parse_pdata(struct mtk_hdmi *hdmi,
>  	of_node_put(remote);
>  
>  	hdmi->ddc_adpt = of_find_i2c_adapter_by_node(i2c_np);
> +	of_node_put(i2c_np);
>  	if (!hdmi->ddc_adpt) {
>  		dev_err(dev, "Failed to get ddc i2c adapter by node\n");
>  		return -EINVAL;



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[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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