[PATCH 1/2] hwmon: (sht4x) Add missing locks

[Guenter Roeck <linux@roeck-us.net>]

Sashiko reports:

Heater sysfs callbacks (heater_enable_store, heater_power_store, and
heater_time_store) are exposed to data races without the hwmon lock.

If a user-space process reads hwmon data while another process enables
the heater, heater_enable_store() executes without holding
hwmon_lock(dev). This can interleave I2C commands and mutate shared
state (data->heating_complete and data->data_pending) concurrently
with sht4x_read_values(), leading to corrupted I2C sequences.

Fixes: 53dfa12299c1 ("hwmon: (sht4x) Rely on subsystem locking")
Cc: Alessandro Zini <alessandro.zini@siemens.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/sht4x.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c
index 9cace0e8acda..7a0dc2ed723d 100644
--- a/drivers/hwmon/sht4x.c
+++ b/drivers/hwmon/sht4x.c
@@ -277,6 +277,8 @@ static ssize_t heater_enable_store(struct device *dev,
 		heating_time_bound = 1100;
 	}
 
+	guard(hwmon_lock)(dev);
+
 	if (time_before(jiffies, data->heating_complete))
 		return -EBUSY;
 
@@ -314,6 +316,8 @@ static ssize_t heater_power_store(struct device *dev,
 	if (power != 20 && power != 110 && power != 200)
 		return -EINVAL;
 
+	guard(hwmon_lock)(dev);
+
 	data->heater_power = power;
 
 	return count;
@@ -344,6 +348,8 @@ static ssize_t heater_time_store(struct device *dev,
 	if (time != 100 && time != 1000)
 		return -EINVAL;
 
+	guard(hwmon_lock)(dev);
+
 	data->heater_time = time;
 
 	return count;
-- 
2.45.2