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>

diff --git a/drivers/hwmon/lm92.c b/drivers/hwmon/lm92.c
index d2060e245ff589f206fbf57c12e62d0038cae0fa..cfaf70b9cba72951e670f16b8700dd4a5ca152cc 100644 (file)
--- a/drivers/hwmon/lm92.c
+++ b/drivers/hwmon/lm92.c
@@ -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;
 }