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Commit 99765db2 authored by Axel Lin's avatar Axel Lin Committed by Guenter Roeck
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hwmon: (lm77) Prevent overflow problem when writing large limits 



On platforms with sizeof(int) < sizeof(long), writing a temperature
limit larger than MAXINT will result in unpredictable limit values
written to the chip.
Clamp the input values to the supported limits first to fix the problem.

For set_temp_hyst:
As Guenter pointed out that the temperature is read as unsigned and stored in
an unsigned long. This is wrong; nothing in the datasheet suggests that the
value (the absolute temperature) must be positive.
So change it to signed.

Signed-off-by: default avatarAxel Lin <axel.lin@ingics.com>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent cf44819c

drivers/hwmon/lm77.c

+6 −5
Original line number Diff line number Diff line
@@ -80,8 +80,7 @@ struct lm77_data { 
 */

static inline s16 LM77_TEMP_TO_REG(int temp)

{

	int ntemp = clamp_val(temp, LM77_TEMP_MIN, LM77_TEMP_MAX);

	return (ntemp / 500) * 8;

	return (temp / 500) * 8;

}



static inline int LM77_TEMP_FROM_REG(s16 reg)
@@ -175,6 +174,7 @@ static ssize_t set_temp(struct device *dev, struct device_attribute *devattr, 
	if (err)

		return err;



	val = clamp_val(val, LM77_TEMP_MIN, LM77_TEMP_MAX);

	mutex_lock(&data->update_lock);

	data->temp[nr] = val;

	lm77_write_value(client, temp_regs[nr], LM77_TEMP_TO_REG(val));
@@ -192,15 +192,16 @@ static ssize_t set_temp_hyst(struct device *dev, 
{

	struct lm77_data *data = dev_get_drvdata(dev);

	struct i2c_client *client = data->client;

	unsigned long val;

	long val;

	int err;



	err = kstrtoul(buf, 10, &val);

	err = kstrtol(buf, 10, &val);

	if (err)

		return err;



	mutex_lock(&data->update_lock);

	data->temp[t_hyst] = data->temp[t_crit] - val;

	val = clamp_val(data->temp[t_crit] - val, LM77_TEMP_MIN, LM77_TEMP_MAX);

	data->temp[t_hyst] = val;

	lm77_write_value(client, LM77_REG_TEMP_HYST,

			 LM77_TEMP_TO_REG(data->temp[t_hyst]));

	mutex_unlock(&data->update_lock);