Re: [PATCH v2 1/2] hwmon: (lm77) Prevent overflow problem when writing large limits

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On 07/31/2014 12:30 AM, Axel Lin wrote:
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.

Signed-off-by: Axel Lin <axel.lin@xxxxxxxxxx>
---
  drivers/hwmon/lm77.c | 6 +++---
  1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/lm77.c b/drivers/hwmon/lm77.c
index 5ceb443..72a02b0 100644
--- a/drivers/hwmon/lm77.c
+++ b/drivers/hwmon/lm77.c
@@ -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)
@@ -176,7 +175,7 @@ static ssize_t set_temp(struct device *dev, struct device_attribute *devattr,
  		return err;

  	mutex_lock(&data->update_lock);
-	data->temp[nr] = val;
+	data->temp[nr] = clamp_val(val, LM77_TEMP_MIN, LM77_TEMP_MAX);
  	lm77_write_value(client, temp_regs[nr], LM77_TEMP_TO_REG(val));

Found it: Clamp applied to data->temp[nr], but you are still using val here.
Has to be LM77_TEMP_TO_REG(data->temp[nr]).

Guenter

  	mutex_unlock(&data->update_lock);
  	return count;
@@ -199,6 +198,7 @@ static ssize_t set_temp_hyst(struct device *dev,
  	if (err)
  		return err;

+	val = clamp_val(val, LM77_TEMP_MIN, LM77_TEMP_MAX);
  	mutex_lock(&data->update_lock);
  	data->temp[t_hyst] = data->temp[t_crit] - val;
  	lm77_write_value(client, LM77_REG_TEMP_HYST,



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