Re: [PATCH v2] thermal: sysfs: Add sanity checks for trip temperature and hysteresis

[Lukasz Luba <lukasz.luba@arm.com>]

On 8/26/24 17:21, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.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 threshold 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.
> 
> Also allow the hysteresis to be updated when the temperature is invalid
> to allow user space to avoid having to adjust hysteresis after a valid
> temperature has been set, but in that case just change the value and do
> nothing else.
> 
> Fixes: be0a3600aa1e ("thermal: sysfs: Rework the handling of trip point updates")
> Cc: 6.8+ <stable@vger.kernel.org> # 6.8+
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> 
> v1 -> v2:
>     * Reorder the new check in trip_point_hyst_store() to be easier
>       to read (Daniel).
>     * Add a comment explaining the ordering of the new check in
>       trip_point_temp_store().
>     * Allow the hysteresis to be updated when the temperature is invalid.
> 
> This is an update of
> 
> https://lore.kernel.org/linux-pm/7719509.EvYhyI6sBW@rjwysocki.net/
> 
> which is being sent separately because patch [1/2] from the original series
> has been applied.
> 
> ---
>   drivers/thermal/thermal_sysfs.c |   50 ++++++++++++++++++++++++++++++----------
>   1 file changed, 38 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 +111,26 @@ 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);
> +	/* Arrange the condition to avoid integer overflows. */
> +	if (temp != THERMAL_TEMP_INVALID &&
> +	    temp <= trip->hysteresis + 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 +160,33 @@ 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;
> +
> +	/*
> +	 * Allow the hysteresis to be updated when the temperature is invalid
> +	 * to allow user space to avoid having to adjust hysteresis after a
> +	 * valid temperature has been set, but in that case just change the
> +	 * value and do nothing else.
> +	 */
> +	if (trip->temperature == THERMAL_TEMP_INVALID) {
> +		WRITE_ONCE(trip->hysteresis, hyst);
> +		goto unlock;
> +	}
>   
> -		__thermal_zone_device_update(tz, THERMAL_TRIP_CHANGED);
> +	if (trip->temperature - hyst <= THERMAL_TEMP_INVALID) {
> +		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
> 
> 
> 


Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>