[PATCH 4.17 018/101] net: macb: Fix ptp time adjustment for large negative delta

From: Greg Kroah-Hartman
Date: Fri Jul 20 2018 - 08:44:12 EST


4.17-stable review patch. If anyone has any objections, please let me know.

------------------

From: Harini Katakam <harini.katakam@xxxxxxxxxx>

[ Upstream commit 64d7839af8c8f67daaf9bf387135052c55d85f90 ]

When delta passed to gem_ptp_adjtime is negative, the sign is
maintained in the ns_to_timespec64 conversion. Hence timespec_add
should be used directly. timespec_sub will just subtract the negative
value thus increasing the time difference.

Signed-off-by: Harini Katakam <harini.katakam@xxxxxxxxxx>
Acked-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/ethernet/cadence/macb_ptp.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

--- a/drivers/net/ethernet/cadence/macb_ptp.c
+++ b/drivers/net/ethernet/cadence/macb_ptp.c
@@ -170,10 +170,7 @@ static int gem_ptp_adjtime(struct ptp_cl

if (delta > TSU_NSEC_MAX_VAL) {
gem_tsu_get_time(&bp->ptp_clock_info, &now);
- if (sign)
- now = timespec64_sub(now, then);
- else
- now = timespec64_add(now, then);
+ now = timespec64_add(now, then);

gem_tsu_set_time(&bp->ptp_clock_info,
(const struct timespec64 *)&now);