[PATCH linux dev-4.10] hwmon (occ): Fix integer overflow in multiplication

[Joel Stanley]

On Sat, Dec 9, 2017 at 8:47 AM, Eddie James <eajames at linux.vnet.ibm.com> wrote:
>
>
> On 12/08/2017 12:16 AM, Joel Stanley wrote:
>>
>> On Thu, Dec 7, 2017 at 5:49 AM, Eddie James <eajames at linux.vnet.ibm.com>
>> wrote:
>>>
>>> --- a/drivers/hwmon/occ/common.c
>>> +++ b/drivers/hwmon/occ/common.c
>>> @@ -468,7 +468,7 @@ static ssize_t occ_show_power_1(struct device *dev,
>>>                                  struct device_attribute *attr, char
>>> *buf)
>>>   {
>>>          int rc;
>>> -       u32 val = 0;
>>> +       u64 val = 0;
>>>          struct power_sensor_1 *power;
>>>          struct occ *occ = dev_get_drvdata(dev);
>>>          struct occ_sensors *sensors = &occ->sensors;
>>> @@ -491,11 +491,11 @@ static ssize_t occ_show_power_1(struct device *dev,
>>>                  val = get_unaligned_be32(&power->accumulator);
>>>                  break;
>>>          case 3:
>>> -               val = get_unaligned_be16(&power->value) * 1000000;
>>> +               val = (u64)get_unaligned_be16(&power->value) *
>>> 1000000ULL;
>>
>> I don't think these casts are required, are they?
>
>
> I'm not at all sure. I didn't think adding ULL was required here, but
> apparently it is. I don't really trust GCC...

Sorry, I thought you were joking here. GCC is behaving as it should.
Hit me up on IRC for an explanation sometime.

Can you resend without the casts?

Cheers,

Joel