linux-kernel - [PATCH v2] thermal: int340x: Protect trip temperature from dynamic update

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Date:   Mon, 23 Jan 2023 09:21:10 -0800
From:   Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     rafael@...nel.org, rui.zhang@...el.com, daniel.lezcano@...aro.org
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        stable@...r.kernel.org
Subject: [PATCH v2] thermal: int340x: Protect trip temperature from dynamic update

Trip temperatures are read using ACPI methods and stored in the memory
during zone initializtion and when the firmware sends a notification for
change. This trip temperature is returned when the thermal core calls via
callback get_trip_temp().

But it is possible that while updating the memory copy of the trips when
the firmware sends a notification for change, thermal core is reading the
trip temperature via the callback get_trip_temp(). This may return invalid
trip temperature.

To address this add a mutex to protect the invalid temperature reads in
the callback get_trip_temp() and int340x_thermal_read_trips().

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc: stable@...r.kernel.org # 5.0+
---
v2:
- rebased on linux-next
- Add ret variable and remove return as suugested by Rafael

 .../int340x_thermal/int340x_thermal_zone.c     | 18 +++++++++++++++---
 .../int340x_thermal/int340x_thermal_zone.h     |  1 +
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/thermal/intel/int340x_thermal/int340x_thermal_zone.c b/drivers/thermal/intel/int340x_thermal/int340x_thermal_zone.c
index 228f44260b27..5fda1e67b793 100644
--- a/drivers/thermal/intel/int340x_thermal/int340x_thermal_zone.c
+++ b/drivers/thermal/intel/int340x_thermal/int340x_thermal_zone.c
@@ -41,7 +41,9 @@ static int int340x_thermal_get_trip_temp(struct thermal_zone_device *zone,
 					 int trip, int *temp)
 {
 	struct int34x_thermal_zone *d = zone->devdata;
-	int i;
+	int i, ret = 0;
+
+	mutex_lock(&d->trip_mutex);
 
 	if (trip < d->aux_trip_nr)
 		*temp = d->aux_trips[trip];
@@ -60,10 +62,12 @@ static int int340x_thermal_get_trip_temp(struct thermal_zone_device *zone,
 			}
 		}
 		if (i == INT340X_THERMAL_MAX_ACT_TRIP_COUNT)
-			return -EINVAL;
+			ret = -EINVAL;
 	}
 
-	return 0;
+	mutex_unlock(&d->trip_mutex);
+
+	return ret;
 }
 
 static int int340x_thermal_get_trip_type(struct thermal_zone_device *zone,
@@ -165,6 +169,8 @@ int int340x_thermal_read_trips(struct int34x_thermal_zone *int34x_zone)
 	int trip_cnt = int34x_zone->aux_trip_nr;
 	int i;
 
+	mutex_lock(&int34x_zone->trip_mutex);
+
 	int34x_zone->crt_trip_id = -1;
 	if (!int340x_thermal_get_trip_config(int34x_zone->adev->handle, "_CRT",
 					     &int34x_zone->crt_temp))
@@ -192,6 +198,8 @@ int int340x_thermal_read_trips(struct int34x_thermal_zone *int34x_zone)
 		int34x_zone->act_trips[i].valid = true;
 	}
 
+	mutex_unlock(&int34x_zone->trip_mutex);
+
 	return trip_cnt;
 }
 EXPORT_SYMBOL_GPL(int340x_thermal_read_trips);
@@ -215,6 +223,8 @@ struct int34x_thermal_zone *int340x_thermal_zone_add(struct acpi_device *adev,
 	if (!int34x_thermal_zone)
 		return ERR_PTR(-ENOMEM);
 
+	mutex_init(&int34x_thermal_zone->trip_mutex);
+
 	int34x_thermal_zone->adev = adev;
 
 	int34x_thermal_zone->ops = kmemdup(&int340x_thermal_zone_ops,
@@ -277,6 +287,7 @@ struct int34x_thermal_zone *int340x_thermal_zone_add(struct acpi_device *adev,
 err_trip_alloc:
 	kfree(int34x_thermal_zone->ops);
 err_ops_alloc:
+	mutex_destroy(&int34x_thermal_zone->trip_mutex);
 	kfree(int34x_thermal_zone);
 	return ERR_PTR(ret);
 }
@@ -289,6 +300,7 @@ void int340x_thermal_zone_remove(struct int34x_thermal_zone
 	acpi_lpat_free_conversion_table(int34x_thermal_zone->lpat_table);
 	kfree(int34x_thermal_zone->aux_trips);
 	kfree(int34x_thermal_zone->ops);
+	mutex_destroy(&int34x_thermal_zone->trip_mutex);
 	kfree(int34x_thermal_zone);
 }
 EXPORT_SYMBOL_GPL(int340x_thermal_zone_remove);
diff --git a/drivers/thermal/intel/int340x_thermal/int340x_thermal_zone.h b/drivers/thermal/intel/int340x_thermal/int340x_thermal_zone.h
index e28ab1ba5e06..6610a9cc441b 100644
--- a/drivers/thermal/intel/int340x_thermal/int340x_thermal_zone.h
+++ b/drivers/thermal/intel/int340x_thermal/int340x_thermal_zone.h
@@ -32,6 +32,7 @@ struct int34x_thermal_zone {
 	struct thermal_zone_device_ops *ops;
 	void *priv_data;
 	struct acpi_lpat_conversion_table *lpat_table;
+	struct mutex trip_mutex;
 };
 
 struct int34x_thermal_zone *int340x_thermal_zone_add(struct acpi_device *,
-- 
2.31.1