On Wed, 31 Mar 2021 17:50:37 +0300
Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> Hello Gwendal Grignou,
>
> The patch dafcf4ed8392: "iio: hrtimer: Allow sub Hz granularity" from
> Feb 25, 2021, leads to the following static checker warning:
>
> drivers/iio/trigger/iio-trig-hrtimer.c:68 iio_hrtimer_store_sampling_frequency()
> warn: assigned value is less than 'u32max'
Coverity + Gustavo spotted this one as well. I've just queued up a fix
based on 1000ULL to ensure the maths is done at appropriate precision.
Thanks,
Jonathan
>
> drivers/iio/trigger/iio-trig-hrtimer.c
> 49 static
> 50 ssize_t iio_hrtimer_store_sampling_frequency(struct device *dev,
> 51 struct device_attribute *attr,
> 52 const char *buf, size_t len)
> 53 {
> 54 struct iio_trigger *trig = to_iio_trigger(dev);
> 55 struct iio_hrtimer_info *info = iio_trigger_get_drvdata(trig);
> 56 unsigned long long val;
> 57 u64 period;
> 58 int integer, fract, ret;
> 59
> 60 ret = iio_str_to_fixpoint(buf, 100, &integer, &fract);
> 61 if (ret)
> 62 return ret;
> 63 if (integer < 0 || fract < 0)
> 64 return -ERANGE;
> 65
> 66 val = fract + 1000 * integer; /* mHz */
> ^^^^^^^^^^^^^^^^^^^^^^
> "fract" and "integer" are integers so the arithmatic will wrap instead
> of going above UINT_MAX
>
> 67
> 68 if (!val || val > UINT_MAX)
> ^^^^^^^^^^^^^^
> Unpossible!
>
> 69 return -EINVAL;
> 70
> 71 info->sampling_frequency[0] = integer; /* Hz */
> 72 info->sampling_frequency[1] = fract * 1000; /* uHz */
> 73 period = PSEC_PER_SEC;
> 74 do_div(period, val);
> 75 info->period = period; /* nS */
> 76
> 77 return len;
> 78 }
>
> regards,
> dan carpenter
