linux-kernel - Re: [PATCH 1/2] cpufreq: sun50i: fix memory leak in dt_has_supported

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Message-ID: <20240510174937.0a710104@donnerap.manchester.arm.com>
Date: Fri, 10 May 2024 17:49:37 +0100
From: Andre Przywara <andre.przywara@....com>
To: Javier Carrasco <javier.carrasco.cruz@...il.com>
Cc: Yangtao Li <tiny.windzz@...il.com>, "Rafael J. Wysocki"
 <rafael@...nel.org>, Viresh Kumar <viresh.kumar@...aro.org>, Chen-Yu Tsai
 <wens@...e.org>, Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland
 <samuel@...lland.org>, Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] cpufreq: sun50i: fix memory leak in
 dt_has_supported_hw()

On Fri, 03 May 2024 19:52:32 +0200
Javier Carrasco <javier.carrasco.cruz@...il.com> wrote:

Hi Javier,

> The for_each_child_of_node() loop does not decrement the child node
> refcount before the break instruction, even though the node is no
> longer required.

Ah, thanks for spotting this, there is indeed a leak. Sorry for the
blunder!

> This can be avoided with the new for_each_child_of_node_scoped() macro
> that removes the need for any of_node_put().

Wow, that's the typical convoluted Linux macro, but it looks correct to me.
It would call the put even if the loop ends naturally, but there is a NULL
test in there, so that's fine.

> Fixes: fa5aec9561cf ("cpufreq: sun50i: Add support for opp_supported_hw")
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.com>

Reviewed-by: Andre Przywara <andre.przywara@....com>

Thanks!
Andre

> ---
>  drivers/cpufreq/sun50i-cpufreq-nvmem.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/sun50i-cpufreq-nvmem.c b/drivers/cpufreq/sun50i-cpufreq-nvmem.c
> index 0b882765cd66..ef83e4bf2639 100644
> --- a/drivers/cpufreq/sun50i-cpufreq-nvmem.c
> +++ b/drivers/cpufreq/sun50i-cpufreq-nvmem.c
> @@ -131,7 +131,7 @@ static const struct of_device_id cpu_opp_match_list[] = {
>  static bool dt_has_supported_hw(void)
>  {
>  	bool has_opp_supported_hw = false;
> -	struct device_node *np, *opp;
> +	struct device_node *np;
>  	struct device *cpu_dev;
>  
>  	cpu_dev = get_cpu_device(0);
> @@ -142,7 +142,7 @@ static bool dt_has_supported_hw(void)
>  	if (!np)
>  		return false;
>  
> -	for_each_child_of_node(np, opp) {
> +	for_each_child_of_node_scoped(np, opp) {
>  		if (of_find_property(opp, "opp-supported-hw", NULL)) {
>  			has_opp_supported_hw = true;
>  			break;
>