[PATCH v2 4/4] media: platform: sti: fix possible object reference leak

[PATCH v2 4/4] media: platform: sti: 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 here after the last
usage.
The of_find_device_by_node() takes a reference to the underlying device
structure, we also should release that reference.

Hans Verkuil says:
The cec driver should never take a reference of the hdmi device.
It never accesses the HDMI device, it only needs the HDMI device pointer as
a key in the notifier list.
The real problem is that several CEC drivers take a reference of the HDMI
device and never release it. So those drivers need to be fixed.

This patch fixes those two issues.

Fixes: fc4e009c6c98 ("[media] stih-cec: add CEC notifier support")
Suggested-by: Hans Verkuil (hansverk) <hansverk@cisco.com>
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: Hans Verkuil (hansverk) <hansverk@cisco.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Wen Yang <yellowriver2010@hotmail.com>
Cc: linux-media@vger.kernel.org
---
v2->v1: 
- move of_node_put() to just after the 'hdmi_dev = of_find_device_by_node(np)'.
- put_device() can be done before the cec = devm_kzalloc line.

 drivers/media/platform/sti/cec/stih-cec.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/media/platform/sti/cec/stih-cec.c b/drivers/media/platform/sti/cec/stih-cec.c
index d34099f..721021f 100644
--- a/drivers/media/platform/sti/cec/stih-cec.c
+++ b/drivers/media/platform/sti/cec/stih-cec.c
@@ -317,9 +317,11 @@ static int stih_cec_probe(struct platform_device *pdev)
 	}
 
 	hdmi_dev = of_find_device_by_node(np);
+	of_node_put(np);
 	if (!hdmi_dev)
 		return -EPROBE_DEFER;
 
+	put_device(&hdmi_dev->dev);
 	cec->notifier = cec_notifier_get(&hdmi_dev->dev);
 	if (!cec->notifier)
 		return -ENOMEM;
-- 
2.9.5

Re: [PATCH v2 4/4] media: platform: sti: fix possible object reference leak

[Benjamin Gaignard]

Le mer. 13 févr. 2019 à 00:49, Wen Yang <wen.yang99@zte.com.cn> a écrit :
>
> The call to of_parse_phandle() returns a node pointer with refcount
> incremented thus it must be explicitly decremented here after the last
> usage.
> The of_find_device_by_node() takes a reference to the underlying device
> structure, we also should release that reference.
>
> Hans Verkuil says:
> The cec driver should never take a reference of the hdmi device.
> It never accesses the HDMI device, it only needs the HDMI device pointer as
> a key in the notifier list.
> The real problem is that several CEC drivers take a reference of the HDMI
> device and never release it. So those drivers need to be fixed.
>
> This patch fixes those two issues.

Reviewed-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>

>
> Fixes: fc4e009c6c98 ("[media] stih-cec: add CEC notifier support")
> Suggested-by: Hans Verkuil (hansverk) <hansverk@cisco.com>
> Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
> Cc: Hans Verkuil (hansverk) <hansverk@cisco.com>
> Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: Wen Yang <yellowriver2010@hotmail.com>
> Cc: linux-media@vger.kernel.org
> ---
> v2->v1:
> - move of_node_put() to just after the 'hdmi_dev = of_find_device_by_node(np)'.
> - put_device() can be done before the cec = devm_kzalloc line.
>
>  drivers/media/platform/sti/cec/stih-cec.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/media/platform/sti/cec/stih-cec.c b/drivers/media/platform/sti/cec/stih-cec.c
> index d34099f..721021f 100644
> --- a/drivers/media/platform/sti/cec/stih-cec.c
> +++ b/drivers/media/platform/sti/cec/stih-cec.c
> @@ -317,9 +317,11 @@ static int stih_cec_probe(struct platform_device *pdev)
>         }
>
>         hdmi_dev = of_find_device_by_node(np);
> +       of_node_put(np);
>         if (!hdmi_dev)
>                 return -EPROBE_DEFER;
>
> +       put_device(&hdmi_dev->dev);
>         cec->notifier = cec_notifier_get(&hdmi_dev->dev);
>         if (!cec->notifier)
>                 return -ENOMEM;
> --
> 2.9.5
>