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

[Vladimir Oltean]

The way we define the phase (the difference between the time of the
signal's rising edge, and the closest integer multiple of the period),
it doesn't make sense to have a phase value larger than 1 period.

So deny these settings coming from the user.

Signed-off-by: Vladimir Oltean <olte...@gmail.com>
---
 drivers/ptp/ptp_chardev.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index e0e6f85966e1..02fcd5e8b998 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -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;
+                               }
+                       }
                } else if (cmd == PTP_PEROUT_REQUEST) {
                        req.perout.flags &= PTP_PEROUT_V1_VALID_FLAGS;
                        req.perout.rsv[0] = 0;
-- 
2.25.1