[PATCH] hwmon: (ntc_thermistor): Avoid overflow

[PATCH] hwmon: (ntc_thermistor): Avoid overflow

[Doug Anderson]

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>
---
 drivers/hwmon/ntc_thermistor.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/ntc_thermistor.c b/drivers/hwmon/ntc_thermistor.c
index 8c23203..8a17f01 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[] = {
-- 
1.9.0.rc1.175.g0b1dcb5

[lm-sensors] [PATCH] hwmon: (ntc_thermistor): Avoid overflow

[Doug Anderson]

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>
---
 drivers/hwmon/ntc_thermistor.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/ntc_thermistor.c b/drivers/hwmon/ntc_thermistor.c
index 8c23203..8a17f01 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[] = {
-- 
1.9.0.rc1.175.g0b1dcb5


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Re: [PATCH] hwmon: (ntc_thermistor): Avoid overflow

[Guenter Roeck]

On 02/13/2014 02:39 PM, Doug Anderson wrote:
> 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>

Nice catch. Applied.

Thanks,
Guenter

Re: [lm-sensors] [PATCH] hwmon: (ntc_thermistor): Avoid overflow

[Guenter Roeck]

On 02/13/2014 02:39 PM, Doug Anderson wrote:
> 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>

Nice catch. Applied.

Thanks,
Guenter



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