Re: [PATCH net-next] ptp: only allow phase values lower than 1 period

Richard Cochran
2020-08-04T23:23:41Z

On Mon, Aug 03, 2020 at 10:49:21PM +0300, Vladimir Oltean wrote:
> @@ -218,6 +218,19 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
> break;
> }
> }
> + if (perout->flags & PTP_PEROUT_PHASE) {
> + /*
> + * The phase should be specified modulo the
> + * period, therefore anything larger than 1
> + * period is invalid.
> + */
> + if (perout->phase.sec > perout->period.sec ||
> + (perout->phase.sec == perout->period.sec &&
> + perout->phase.nsec > perout->period.nsec)) {
> + err = -ERANGE;
> + break;
> + }

So if perout->period={1,0} and perout->phase={1,0} then the phase has
wrapped 360 degrees back to zero.

Shouldn't this code catch that case as well?

So why not test for (perout->phase.nsec >= perout->period.nsec) instead?

Thanks,
Richard