From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Commit 0dc23567c206 ("thermal: core: Move lists of thermal instances
to trip descriptors") overlooked the case in which the Power Allocator
governor attempts to bind to a tripless thermal zone and params->trip_max
is NULL in check_power_actors().

No power actors can be found in that case, so check_power_actors() needs
to be made return 0 then to restore its previous behavior.

Fixes: 0dc23567c206 ("thermal: core: Move lists of thermal instances to trip descriptors")
Closes: https://lore.kernel.org/linux-pm/Z0NeGF4ryCe_b5rr@sashalap/
Reported-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/thermal/gov_power_allocator.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/thermal/gov_power_allocator.c
===================================================================
--- linux-pm.orig/drivers/thermal/gov_power_allocator.c
+++ linux-pm/drivers/thermal/gov_power_allocator.c
@@ -588,10 +588,15 @@ static void allow_maximum_power(struct t
 static int check_power_actors(struct thermal_zone_device *tz,
 			      struct power_allocator_params *params)
 {
-	const struct thermal_trip_desc *td = trip_to_trip_desc(params->trip_max);
+	const struct thermal_trip_desc *td;
 	struct thermal_instance *instance;
 	int ret = 0;
 
+	if (!params->trip_max)
+		return 0;
+
+	td = trip_to_trip_desc(params->trip_max);
+
 	list_for_each_entry(instance, &td->thermal_instances, trip_node) {
 		if (!cdev_is_power_actor(instance->cdev)) {
 			dev_warn(&tz->device, "power_allocator: %s is not a power actor\n",

On 11/25/24 11:24, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> Commit 0dc23567c206 ("thermal: core: Move lists of thermal instances
> to trip descriptors") overlooked the case in which the Power Allocator
> governor attempts to bind to a tripless thermal zone and params->trip_max
> is NULL in check_power_actors().

That corner case sneaked in...

> 
> No power actors can be found in that case, so check_power_actors() needs
> to be made return 0 then to restore its previous behavior.
> 
> Fixes: 0dc23567c206 ("thermal: core: Move lists of thermal instances to trip descriptors")
> Closes: https://lore.kernel.org/linux-pm/Z0NeGF4ryCe_b5rr@sashalap/
> Reported-by: Sasha Levin <sashal@kernel.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>   drivers/thermal/gov_power_allocator.c |    7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> Index: linux-pm/drivers/thermal/gov_power_allocator.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/gov_power_allocator.c
> +++ linux-pm/drivers/thermal/gov_power_allocator.c
> @@ -588,10 +588,15 @@ static void allow_maximum_power(struct t
>   static int check_power_actors(struct thermal_zone_device *tz,
>   			      struct power_allocator_params *params)
>   {
> -	const struct thermal_trip_desc *td = trip_to_trip_desc(params->trip_max);
> +	const struct thermal_trip_desc *td;
>   	struct thermal_instance *instance;
>   	int ret = 0;
>   
> +	if (!params->trip_max)
> +		return 0;

Yes, 0 is the right thing to return here, since we might get later some
trip points.

> +
> +	td = trip_to_trip_desc(params->trip_max);
> +
>   	list_for_each_entry(instance, &td->thermal_instances, trip_node) {
>   		if (!cdev_is_power_actor(instance->cdev)) {
>   			dev_warn(&tz->device, "power_allocator: %s is not a power actor\n",
> 
> 
> 

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