hwmon: (nct7802) Fix overflows seen when writing into limit attributes

Fix overflows seen when writing voltage and temperature limit attributes.

The value passed to DIV_ROUND_CLOSEST() needs to be clamped, and the
value parameter passed to nct7802_write_fan_min() is an unsigned long.

Also, writing values larger than 2700000 into a fan limit attribute results
in writing 0 into the chip's limit registers. The exact behavior when
writing this value is unspecified. For consistency, report a limit of
1350000 if the chip register reads 0. This may be wrong, and the chip
behavior should be verified with the actual chip, but it is better than
reporting a value of 0 (which, when written, results in writing a value
of 0x1fff into the chip register).

Fixes: 3434f3783580 ("hwmon: Driver for Nuvoton NCT7802Y")
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/drivers/hwmon/nct7802.c b/drivers/hwmon/nct7802.c
index 3ce33d244cc0f7a0a31f2f1af4b7cdf92f5341e2..12b94b094c0d154eba138ec1845ed2c842cb887f 100644 (file)
--- a/drivers/hwmon/nct7802.c
+++ b/drivers/hwmon/nct7802.c
@@ -259,13 +259,15 @@ static int nct7802_read_fan_min(struct nct7802_data *data, u8 reg_fan_low,
                ret = 0;
        else if (ret)
                ret = DIV_ROUND_CLOSEST(1350000U, ret);
+       else
+               ret = 1350000U;
 abort:
        mutex_unlock(&data->access_lock);
        return ret;
 }
 
 static int nct7802_write_fan_min(struct nct7802_data *data, u8 reg_fan_low,
-                                u8 reg_fan_high, unsigned int limit)
+                                u8 reg_fan_high, unsigned long limit)
 {
        int err;
 
@@ -326,8 +328,8 @@ static int nct7802_write_voltage(struct nct7802_data *data, int nr, int index,
        int shift = 8 - REG_VOLTAGE_LIMIT_MSB_SHIFT[index - 1][nr];
        int err;
 
+       voltage = clamp_val(voltage, 0, 0x3ff * nct7802_vmul[nr]);
        voltage = DIV_ROUND_CLOSEST(voltage, nct7802_vmul[nr]);
-       voltage = clamp_val(voltage, 0, 0x3ff);
 
        mutex_lock(&data->access_lock);
        err = regmap_write(data->regmap,
@@ -402,7 +404,7 @@ static ssize_t store_temp(struct device *dev, struct device_attribute *attr,
        if (err < 0)
                return err;
 
-       val = clamp_val(DIV_ROUND_CLOSEST(val, 1000), -128, 127);
+       val = DIV_ROUND_CLOSEST(clamp_val(val, -128000, 127000), 1000);
 
        err = regmap_write(data->regmap, nr, val & 0xff);
        return err ? : count;