[PATCH v5] net/mlx5: Fix PTP event stack info leak and NULL ptp_clock use

[Prathamesh Deshpande <prathameshdeshpande7@gmail.com>]

In mlx5_pps_event(), ptp_event is not zero-initialized. Since it contains
a union, partial assignment can leave stale stack data in unused members.

Also, clock->ptp may be NULL if ptp_clock_register() fails.

Fix by zero-initializing ptp_event, using a local timestamp variable for
event data assignment, and guarding ptp_clock_event() with a NULL check.

Fixes: 7c39afb394c7 ("net/mlx5: PTP code migration to driver core section")
Signed-off-by: Prathamesh Deshpande <prathameshdeshpande7@gmail.com>
---
v5:
- Drop MAX_PIN_NUM check per review.
- Drop pin_config local guard to keep this revision narrowly scoped.
v4:
- Validate pin index against MAX_PIN_NUM instead of n_pins.
v3:
- Fix union corruption by using a local timestamp variable.
- Validate pin index against n_pins with WARN_ON_ONCE.
- Remove redundant pin < 0 check and cleanup TODO comment.
v2:
- Zero-initialize ptp_event to prevent stack information leak.
- Add bounds check for hardware pin index to prevent OOB access.
- Add NULL guard for pin_config to handle initialization failures.
- Add NULL check for clock->ptp as originally intended.

 drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
index bd4e042077af..77d7b81a0a25 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
@@ -1164,7 +1164,7 @@ static int mlx5_pps_event(struct notifier_block *nb,
 							       pps_nb);
 	struct mlx5_core_dev *mdev = clock_state->mdev;
 	struct mlx5_clock *clock = mdev->clock;
-	struct ptp_clock_event ptp_event;
+	struct ptp_clock_event ptp_event = {};
 	struct mlx5_eqe *eqe = data;
 	int pin = eqe->data.pps.pin;
 	unsigned long flags;
@@ -1173,7 +1173,7 @@ static int mlx5_pps_event(struct notifier_block *nb,
 	switch (clock->ptp_info.pin_config[pin].func) {
 	case PTP_PF_EXTTS:
 		ptp_event.index = pin;
-		ptp_event.timestamp = mlx5_real_time_mode(mdev) ?
+		ns = mlx5_real_time_mode(mdev) ?
 			mlx5_real_time_cyc2time(clock,
 						be64_to_cpu(eqe->data.pps.time_stamp)) :
 			mlx5_timecounter_cyc2time(clock,
@@ -1181,12 +1181,13 @@ static int mlx5_pps_event(struct notifier_block *nb,
 		if (clock->pps_info.enabled) {
 			ptp_event.type = PTP_CLOCK_PPSUSR;
 			ptp_event.pps_times.ts_real =
-					ns_to_timespec64(ptp_event.timestamp);
+					ns_to_timespec64(ns);
 		} else {
 			ptp_event.type = PTP_CLOCK_EXTTS;
+			ptp_event.timestamp = ns;
 		}
-		/* TODOL clock->ptp can be NULL if ptp_clock_register fails */
-		ptp_clock_event(clock->ptp, &ptp_event);
+		if (clock->ptp)
+			ptp_clock_event(clock->ptp, &ptp_event);
 		break;
 	case PTP_PF_PEROUT:
 		if (clock->shared) {
-- 
2.43.0