linux-kernel - Re: [PATCH v1 2/2] thermal: sysfs: Add sanity checks for trip temperature and hysteresis

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Message-ID: <cb8bbde9-1b13-4c63-960d-5846a319f5ea@linaro.org>
Date: Fri, 23 Aug 2024 17:26:00 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
 Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Zhang Rui <rui.zhang@...el.com>,
 Lukasz Luba <lukasz.luba@....com>, Peter Kästle
 <peter@...e.net>
Subject: Re: [PATCH v1 2/2] thermal: sysfs: Add sanity checks for trip
 temperature and hysteresis

On 22/08/2024 21:48, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Add sanity checks for new trip temperature and hysteresis values to
> trip_point_temp_store() and trip_point_hyst_store() to prevent trip
> point thresholds from falling below THERMAL_TEMP_INVALID.
> 
> However, still allow user space to pass THERMAL_TEMP_INVALID as the
> new trip temperature value to invalidate the trip if necessary.
> 
> Fixes: be0a3600aa1e ("thermal: sysfs: Rework the handling of trip point updates")
> Cc: 6.8+ <stable@...r.kernel.org> # 6.8+
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>   drivers/thermal/thermal_sysfs.c |   38 ++++++++++++++++++++++++++------------
>   1 file changed, 26 insertions(+), 12 deletions(-)
> 
> Index: linux-pm/drivers/thermal/thermal_sysfs.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_sysfs.c
> +++ linux-pm/drivers/thermal/thermal_sysfs.c
> @@ -111,18 +111,25 @@ trip_point_temp_store(struct device *dev
>   
>   	mutex_lock(&tz->lock);
>   
> -	if (temp != trip->temperature) {
> -		if (tz->ops.set_trip_temp) {
> -			ret = tz->ops.set_trip_temp(tz, trip, temp);
> -			if (ret)
> -				goto unlock;
> -		}
> +	if (temp == trip->temperature)
> +		goto unlock;
>   
> -		thermal_zone_set_trip_temp(tz, trip, temp);
> +	if (temp != THERMAL_TEMP_INVALID &&
> +	    temp <= trip->hysteresis + THERMAL_TEMP_INVALID) {

It seems to me the condition is hard to understand.

   temp <= trip->hysteresis + THERMAL_TEMP_INVALID

	  ==>

   temp - trip->hysteresis <= THERMAL_TEMP_INVALID


Could be the test below simpler to understand ?

	if (trip->hysteresis &&
	    temp - trip->hysteresis < THERMAL_TEMP_INVALID))

I think more sanity check may be needed also.

	if (temp < THERMAL_TEMP_INVALID)

> +		ret = -EINVAL;
> +		goto unlock;
> +	}
>   
> -		__thermal_zone_device_update(tz, THERMAL_TRIP_CHANGED);
> +	if (tz->ops.set_trip_temp) {
> +		ret = tz->ops.set_trip_temp(tz, trip, temp);
> +		if (ret)
> +			goto unlock;
>   	}
>   
> +	thermal_zone_set_trip_temp(tz, trip, temp);
> +
> +	__thermal_zone_device_update(tz, THERMAL_TRIP_CHANGED);
> +
>   unlock:
>   	mutex_unlock(&tz->lock);
>   
> @@ -152,15 +159,22 @@ trip_point_hyst_store(struct device *dev
>   
>   	mutex_lock(&tz->lock);
>   
> -	if (hyst != trip->hysteresis) {
> -		thermal_zone_set_trip_hyst(tz, trip, hyst);
> +	if (hyst == trip->hysteresis)
> +		goto unlock;
>   
> -		__thermal_zone_device_update(tz, THERMAL_TRIP_CHANGED);
> +	if (hyst + THERMAL_TEMP_INVALID >= trip->temperature) {
> +		ret = -EINVAL;
> +		goto unlock;
>   	}
>   
> +	thermal_zone_set_trip_hyst(tz, trip, hyst);
> +
> +	__thermal_zone_device_update(tz, THERMAL_TRIP_CHANGED);
> +
> +unlock:
>   	mutex_unlock(&tz->lock);
>   
> -	return count;
> +	return ret ? ret : count;
>   }
>   
>   static ssize_t
> 
> 
> 


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