From 007be4327e443d79c9dd9e56dc16c36f6395d208 Mon Sep 17 00:00:00 2001 From: Gui-Dong Han Date: Tue, 3 Feb 2026 20:14:43 +0800 Subject: [PATCH] hwmon: (max16065) Use READ/WRITE_ONCE to avoid compiler optimization induced race Simply copying shared data to a local variable cannot prevent data races. The compiler is allowed to optimize away the local copy and re-read the shared memory, causing a Time-of-Check Time-of-Use (TOCTOU) issue if the data changes between the check and the usage. To enforce the use of the local variable, use READ_ONCE() when reading the shared data and WRITE_ONCE() when updating it. Apply these macros to the three identified locations (curr_sense, adc, and fault) where local variables are used for error validation, ensuring the value remains consistent. Reported-by: Ben Hutchings Closes: https://lore.kernel.org/all/6fe17868327207e8b850cf9f88b7dc58b2021f73.camel@decadent.org.uk/ Fixes: f5bae2642e3d ("hwmon: Driver for MAX16065 System Manager and compatibles") Fixes: b8d5acdcf525 ("hwmon: (max16065) Use local variable to avoid TOCTOU") Cc: stable@vger.kernel.org Signed-off-by: Gui-Dong Han Link: https://lore.kernel.org/r/20260203121443.5482-1-hanguidong02@gmail.com Signed-off-by: Guenter Roeck --- drivers/hwmon/max16065.c | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-) diff --git a/drivers/hwmon/max16065.c b/drivers/hwmon/max16065.c index 4c9e7892a73c1..43fbb9b26b102 100644 --- a/drivers/hwmon/max16065.c +++ b/drivers/hwmon/max16065.c @@ -151,27 +151,27 @@ static struct max16065_data *max16065_update_device(struct device *dev) int i; for (i = 0; i < data->num_adc; i++) - data->adc[i] - = max16065_read_adc(client, MAX16065_ADC(i)); + WRITE_ONCE(data->adc[i], + max16065_read_adc(client, MAX16065_ADC(i))); if (data->have_current) { - data->adc[MAX16065_NUM_ADC] - = max16065_read_adc(client, MAX16065_CSP_ADC); - data->curr_sense - = i2c_smbus_read_byte_data(client, - MAX16065_CURR_SENSE); + WRITE_ONCE(data->adc[MAX16065_NUM_ADC], + max16065_read_adc(client, MAX16065_CSP_ADC)); + WRITE_ONCE(data->curr_sense, + i2c_smbus_read_byte_data(client, MAX16065_CURR_SENSE)); } for (i = 0; i < 2; i++) - data->fault[i] - = i2c_smbus_read_byte_data(client, MAX16065_FAULT(i)); + WRITE_ONCE(data->fault[i], + i2c_smbus_read_byte_data(client, MAX16065_FAULT(i))); /* * MAX16067 and MAX16068 have separate undervoltage and * overvoltage alarm bits. Squash them together. */ if (data->chip == max16067 || data->chip == max16068) - data->fault[0] |= data->fault[1]; + WRITE_ONCE(data->fault[0], + data->fault[0] | data->fault[1]); data->last_updated = jiffies; data->valid = true; @@ -185,7 +185,7 @@ static ssize_t max16065_alarm_show(struct device *dev, { struct sensor_device_attribute_2 *attr2 = to_sensor_dev_attr_2(da); struct max16065_data *data = max16065_update_device(dev); - int val = data->fault[attr2->nr]; + int val = READ_ONCE(data->fault[attr2->nr]); if (val < 0) return val; @@ -203,7 +203,7 @@ static ssize_t max16065_input_show(struct device *dev, { struct sensor_device_attribute *attr = to_sensor_dev_attr(da); struct max16065_data *data = max16065_update_device(dev); - int adc = data->adc[attr->index]; + int adc = READ_ONCE(data->adc[attr->index]); if (unlikely(adc < 0)) return adc; @@ -216,7 +216,7 @@ static ssize_t max16065_current_show(struct device *dev, struct device_attribute *da, char *buf) { struct max16065_data *data = max16065_update_device(dev); - int curr_sense = data->curr_sense; + int curr_sense = READ_ONCE(data->curr_sense); if (unlikely(curr_sense < 0)) return curr_sense; -- 2.47.3