[PATCH v3] net/mlx5: Fix OOB access and stack information leak in PTP event handling

[Prathamesh Deshpande <prathameshdeshpande7@gmail.com>]

In mlx5_pps_event(), several critical issues were identified during
review by Sashiko:

1. The 'pin' index from the hardware event was used without bounds
   checking to index 'pin_config' and 'pps_info->start', leading to
   potential out-of-bounds memory access.
2. 'ptp_event' was not zero-initialized. Since it contains a union,
   assigning a timestamp partially leaves the 'ts_raw' field with
   uninitialized stack memory, which can leak kernel data or
   corrupt time sync logic in hardpps().
3. A NULL 'pin_config' could be dereferenced if initialization failed.
4. 'clock->ptp' could be NULL if ptp_clock_register() failed.

Fix these by zero-initializing the event struct, adding a bounds
check against n_pins, and adding appropriate NULL guards.

Fixes: 7c39afb394c7 ("net/mlx5: PTP code migration to driver core section")
Suggested-by: Carolina Jubran <cjubran@nvidia.com>
Signed-off-by: Prathamesh Deshpande <prathameshdeshpande7@gmail.com>
---
v3:
- Fix union corruption by using a local timestamp variable [Sashiko].
- Validate pin index against n_pins with WARN_ON_ONCE [Carolina].
- Remove redundant pin < 0 check and cleanup TODO comment.
v2:
- Zero-initialize ptp_event to prevent stack information leak [Sashiko].
- Add bounds check for hardware pin index to prevent OOB access [Sashiko].
- Add NULL guard for pin_config to handle initialization failures [Sashiko].
- Add NULL check for clock->ptp as originally intended.

 .../net/ethernet/mellanox/mlx5/core/lib/clock.c | 17 ++++++++++++-----
 1 file changed, 12 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..674dd048a6b8 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
@@ -1164,16 +1164,22 @@ 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;
 	u64 ns;
 
+	if (!clock->ptp_info.pin_config)
+		return NOTIFY_OK;
+
+	if (WARN_ON_ONCE(pin >= clock->ptp_info.n_pins))
+		return NOTIFY_OK;
+
 	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 +1187,13 @@ 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