Re: [PATCH] staging: vchiq_arm: Fix missing refcount decrement in error path for fw_node

[Umang Jain <umang.jain@ideasonboard.com>]

Hi Javier,

Thank you for the patch.

On 13/10/24 4:12 pm, Javier Carrasco wrote:
> An error path was introduced without including the required call to
> of_node_put() to decrement the node's refcount and avoid leaking memory.
> If the call to kzalloc() for 'mgmt' fails, the probe returns without
> decrementing the refcount.
>
> Use the automatic cleanup facility to fix the bug and protect the code
> against new error paths where the call to of_node_put() might be missing
> again.
>
> Cc: stable@vger.kernel.org
> Fixes: 1c9e16b73166 ("staging: vc04_services: vchiq_arm: Split driver static and runtime data")
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
> ---
>   drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> index 27ceaac8f6cc..792cf3a807e1 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> @@ -1332,7 +1332,8 @@ MODULE_DEVICE_TABLE(of, vchiq_of_match);
>   
>   static int vchiq_probe(struct platform_device *pdev)
>   {
> -	struct device_node *fw_node;
> +	struct device_node *fw_node __free(device_node) =
> +		of_find_compatible_node(NULL, NULL, "raspberrypi,bcm2835-firmware");

How about :

+	struct device_node *fw_node __free(device_node) = NULL;

>   	const struct vchiq_platform_info *info;
>   	struct vchiq_drv_mgmt *mgmt;
>   	int ret;
> @@ -1341,8 +1342,6 @@ static int vchiq_probe(struct platform_device *pdev)
>   	if (!info)
>   		return -EINVAL;
>   
> -	fw_node = of_find_compatible_node(NULL, NULL,
> -					  "raspberrypi,bcm2835-firmware");

And undo this (i.e. keep the of_find_compatible_node() call here

This helps with readability as there is a NULL check just after this.
>   	if (!fw_node) {
>   		dev_err(&pdev->dev, "Missing firmware node\n");
>   		return -ENOENT;
> @@ -1353,7 +1352,6 @@ static int vchiq_probe(struct platform_device *pdev)
>   		return -ENOMEM;
>   
>   	mgmt->fw = devm_rpi_firmware_get(&pdev->dev, fw_node);
> -	of_node_put(fw_node);

And this change remains the same.
>   	if (!mgmt->fw)
>   		return -EPROBE_DEFER;
>   
>
> ---
> base-commit: d61a00525464bfc5fe92c6ad713350988e492b88
> change-id: 20241013-vchiq_arm-of_node_put-60a5eaaafd70
>
> Best regards,