linux-kernel - Re: [PATCH] staging: vchiq_arm: Fix missing refcount decrement in error path for fw

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Message-ID: <a4283afc-f869-4048-90b4-1775acb9adda@stanley.mountain>
Date: Mon, 14 Oct 2024 10:22:05 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Javier Carrasco <javier.carrasco.cruz@...il.com>
Cc: Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Stefan Wahren <wahrenst@....net>,
	Umang Jain <umang.jain@...asonboard.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-staging@...ts.linux.dev,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] staging: vchiq_arm: Fix missing refcount decrement in
 error path for fw_node

On Sun, Oct 13, 2024 at 12:42:32PM +0200, 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@...r.kernel.org
> Fixes: 1c9e16b73166 ("staging: vc04_services: vchiq_arm: Split driver static and runtime data")
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.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");
>  	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");

Perhaps it's better to declare the variable here so that the function and the
error handling are next to each other.

	if (!info)
		return -EINVAL;

	struct device_node *fw_node __free(device_node) =
		of_find_compatible_node(NULL, NULL, "raspberrypi,bcm2835-firmware");
	if (!fw_node) {

	...

This is why we lifted the rule that variables had to be declared at the start
of a function.

regards,
dan carpenter