Commit 5b963089 authored Aug 05, 2014 by Axel Lin Committed by Guenter Roeck Aug 05, 2014

hwmon: (lm92) 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. Avoid auto-conversion from long to int to fix
the problem.

The hysteresis temperature range depends on the value of
data->temp[attr->index], since val is subtracted from it.
Use a wider clamp, [-120000, 220000] should do to cover the
possible range. Also add missing TEMP_TO_REG() on writes into
cached hysteresis value.

Also uses clamp_val to simplify the code a bit.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
[Guenter Roeck: Fixed double TEMP_TO_REG on hysteresis updates]
Cc: stable@vger.kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

parent f4d33337

drivers/hwmon/lm92.c

+6 −7

Original line number	Diff line number	Diff line
		@@ -74,12 +74,9 @@ static inline int TEMP_FROM_REG(s16 reg)
		return reg / 8 * 625 / 10;
		}

		static inline s16 TEMP_TO_REG(int val)
		static inline s16 TEMP_TO_REG(long val)
		{
		if (val <= -60000)
		return -60000 * 10 / 625 * 8;
		if (val >= 160000)
		return 160000 * 10 / 625 * 8;
		val = clamp_val(val, -60000, 160000);
		return val * 10 / 625 * 8;
		}

		@@ -206,10 +203,12 @@ static ssize_t set_temp_hyst(struct device *dev,
		if (err)
		return err;

		val = clamp_val(val, -120000, 220000);
		mutex_lock(&data->update_lock);
		data->temp[t_hyst] = TEMP_FROM_REG(data->temp[attr->index]) - val;
		data->temp[t_hyst] =
		TEMP_TO_REG(TEMP_FROM_REG(data->temp[attr->index]) - val);
		i2c_smbus_write_word_swapped(client, LM92_REG_TEMP_HYST,
		TEMP_TO_REG(data->temp[t_hyst]));
		data->temp[t_hyst]);
		mutex_unlock(&data->update_lock);
		return count;
		}