hwmon: (ntc_thermistor) Avoid math overflow

commit d3d89c468ceebbcf9423d1a3d66c5bf91f569570 upstream.

The ntc thermistor code was doing math whose temporary result might
have overflowed 32-bits.  We need some casts in there to make it safe.

In one example I found:
- pullup_uV: 1800000
- result of iio_read_channel_raw: 3226
- 1800000 * 3226 => 0x15a1cbc80

Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/hwmon/ntc_thermistor.c b/drivers/hwmon/ntc_thermistor.c
index d6d640a733d5..9297164a23a5 100644
--- a/drivers/hwmon/ntc_thermistor.c
+++ b/drivers/hwmon/ntc_thermistor.c
@@ -145,7 +145,7 @@ struct ntc_data {
 static int ntc_adc_iio_read(struct ntc_thermistor_platform_data *pdata)
 {
         struct iio_channel *channel = pdata->chan;
-        unsigned int result;
+        s64 result;
         int val, ret;
 
         ret = iio_read_channel_raw(channel, &val);
@@ -155,10 +155,10 @@ static int ntc_adc_iio_read(struct ntc_thermistor_platform_data *pdata)
         }
 
         /* unit: mV */
-        result = pdata->pullup_uv * val;
+        result = pdata->pullup_uv * (s64) val;
         result >>= 12;
 
-        return result;
+        return (int)result;
 }
 
 static const struct of_device_id ntc_match[] = {