linux-kernel - Re: [PATCH] thermal/of: Fix reference count leak in thermal_of_cm

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Message-ID: <CAJZ5v0hsJaK1DkNu7bRTBDH3U5seT2fmceg=CVpekK_QsVtS0w@mail.gmail.com>
Date: Mon, 27 Oct 2025 21:26:04 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Miaoqian Lin <linmq006@...il.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Daniel Lezcano <daniel.lezcano@...aro.org>, 
	Zhang Rui <rui.zhang@...el.com>, Lukasz Luba <lukasz.luba@....com>, 
	Yu-Che Cheng <giver@...omium.org>, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org
Subject: Re: [PATCH] thermal/of: Fix reference count leak in thermal_of_cm_lookup

On Sun, Oct 26, 2025 at 5:44 PM Miaoqian Lin <linmq006@...il.com> wrote:
>
> The function calls of_parse_phandle() to get a
> device node, which increments the reference count of the node. However,
> the function fails to call of_node_put() to decrement the reference.
> This leads to a reference count leak.
>
> This is found by static analysis and similar to the commit a508e33956b5
> ("ipmi:ipmb: Fix refcount leak in ipmi_ipmb_probe")
>
> Fixes: 423de5b5bc5b ("thermal/of: Fix cdev lookup in thermal_of_should_bind()")
> Cc: stable@...r.kernel.org
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> ---
>  drivers/thermal/thermal_of.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/thermal/thermal_of.c b/drivers/thermal/thermal_of.c
> index 1a51a4d240ff..932291648683 100644
> --- a/drivers/thermal/thermal_of.c
> +++ b/drivers/thermal/thermal_of.c
> @@ -284,8 +284,12 @@ static bool thermal_of_cm_lookup(struct device_node *cm_np,
>                 int count, i;
>
>                 tr_np = of_parse_phandle(child, "trip", 0);
> -               if (tr_np != trip->priv)
> +               if (tr_np != trip->priv) {
> +                       of_node_put(tr_np);
>                         continue;
> +               }
> +
> +               of_node_put(tr_np);

If it can be done here, it may as well be done before the check above.

>
>                 /* The trip has been found, look up the cdev. */
>                 count = of_count_phandle_with_args(child, "cooling-device",
> --

It would be more prudent to hold this reference throughout the scope
though and release it when the scope is left.