From 8ebf05908f0e8ab5d2c50555ed059fa239b31072 Mon Sep 17 00:00:00 2001 From: Armin Wolf Date: Fri, 24 Nov 2023 19:27:47 +0100 Subject: [PATCH] hwmon: (acpi_power_meter) Fix 4.29 MW bug [ Upstream commit 1fefca6c57fb928d2131ff365270cbf863d89c88 ] The ACPI specification says: "If an error occurs while obtaining the meter reading or if the value is not available then an Integer with all bits set is returned" Since the "integer" is 32 bits in case of the ACPI power meter, userspace will get a power reading of 2^32 * 1000 miliwatts (~4.29 MW) in case of such an error. This was discovered due to a lm_sensors bugreport (https://github.com/lm-sensors/lm-sensors/issues/460). Fix this by returning -ENODATA instead. Tested-by: Fixes: de584afa5e18 ("hwmon driver for ACPI 4.0 power meters") Signed-off-by: Armin Wolf Link: https://lore.kernel.org/r/20231124182747.13956-1-W_Armin@gmx.de Signed-off-by: Guenter Roeck Signed-off-by: Sasha Levin --- drivers/hwmon/acpi_power_meter.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/hwmon/acpi_power_meter.c b/drivers/hwmon/acpi_power_meter.c index fa28d44..b772c07 100644 --- a/drivers/hwmon/acpi_power_meter.c +++ b/drivers/hwmon/acpi_power_meter.c @@ -31,6 +31,7 @@ #define POWER_METER_CAN_NOTIFY (1 << 3) #define POWER_METER_IS_BATTERY (1 << 8) #define UNKNOWN_HYSTERESIS 0xFFFFFFFF +#define UNKNOWN_POWER 0xFFFFFFFF #define METER_NOTIFY_CONFIG 0x80 #define METER_NOTIFY_TRIP 0x81 @@ -348,6 +349,9 @@ static ssize_t show_power(struct device *dev, update_meter(resource); mutex_unlock(&resource->lock); + if (resource->power == UNKNOWN_POWER) + return -ENODATA; + return sprintf(buf, "%llu\n", resource->power * 1000); } -- 2.7.4