[PATCH v2] 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 MAX_PIN_NUM, and adding appropriate NULL guards.

Fixes: 7c39afb394c7 ("net/mlx5: PTP code migration to driver core section")

Signed-off-by: Prathamesh Deshpande <prathameshdeshpande7@gmail.com>
---
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.

 drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 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..a4d8c5c39abc 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
@@ -1164,12 +1164,18 @@ 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 (pin < 0 || pin >= MAX_PIN_NUM)
+		return NOTIFY_OK;
+
 	switch (clock->ptp_info.pin_config[pin].func) {
 	case PTP_PF_EXTTS:
 		ptp_event.index = pin;
@@ -1185,8 +1191,8 @@ static int mlx5_pps_event(struct notifier_block *nb,
 		} else {
 			ptp_event.type = PTP_CLOCK_EXTTS;
 		}
-		/* 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