[PATCH 5.15.y 3/3] net: ravb: avoid dereferencing an invalid PTP clock

[Sasha Levin <sashal@kernel.org>]

From: Xuanqiang Luo <luoxuanqiang@kylinos.cn>

[ Upstream commit 1f77af0aaf277413ff32f6ff8c2c4282bd64c897 ]

The PTP clock is unavailable before the first open, so querying its
index can dereference a NULL pointer. Registration failures can also
leave an error pointer in priv->ptp.clock.

Cache the PHC index separately and report -1 while no clock is
registered. Normalize registration errors to NULL and preserve the
static timestamping capabilities.

Fixes: a0d2f20650e8 ("Renesas Ethernet AVB PTP clock driver")
Cc: stable@vger.kernel.org
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Signed-off-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
Link: https://patch.msgid.link/20260811103733.62599-2-xuanqiang.luo@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/renesas/ravb.h      |  1 +
 drivers/net/ethernet/renesas/ravb_main.c |  3 ++-
 drivers/net/ethernet/renesas/ravb_ptp.c  | 15 +++++++++++++--
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index a475f54a6b63c..33486234c1218 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -973,6 +973,7 @@ struct ravb_ptp_perout {
 struct ravb_ptp {
 	struct ptp_clock *clock;
 	struct ptp_clock_info info;
+	int phc_index;
 	u32 default_addend;
 	u32 current_addend;
 	int extts[N_EXT_TS];
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 2e36be812945a..9b7b66fcfce8d 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1334,7 +1334,7 @@ static int ravb_get_ts_info(struct net_device *ndev,
 			(1 << HWTSTAMP_FILTER_NONE) |
 			(1 << HWTSTAMP_FILTER_PTP_V2_L2_EVENT) |
 			(1 << HWTSTAMP_FILTER_ALL);
-		info->phc_index = ptp_clock_index(priv->ptp.clock);
+		info->phc_index = READ_ONCE(priv->ptp.phc_index);
 	}
 
 	return 0;
@@ -2247,6 +2247,7 @@ static int ravb_probe(struct platform_device *pdev)
 	priv->rstc = rstc;
 	priv->ndev = ndev;
 	priv->pdev = pdev;
+	priv->ptp.phc_index = -1;
 	priv->num_tx_ring[RAVB_BE] = BE_TX_RING_SIZE;
 	priv->num_rx_ring[RAVB_BE] = BE_RX_RING_SIZE;
 	priv->num_tx_ring[RAVB_NC] = NC_TX_RING_SIZE;
diff --git a/drivers/net/ethernet/renesas/ravb_ptp.c b/drivers/net/ethernet/renesas/ravb_ptp.c
index c099656dd75b6..ac73ca2a98f8d 100644
--- a/drivers/net/ethernet/renesas/ravb_ptp.c
+++ b/drivers/net/ethernet/renesas/ravb_ptp.c
@@ -332,6 +332,7 @@ void ravb_ptp_interrupt(struct net_device *ndev)
 void ravb_ptp_init(struct net_device *ndev, struct platform_device *pdev)
 {
 	struct ravb_private *priv = netdev_priv(ndev);
+	struct ptp_clock *clock;
 	unsigned long flags;
 
 	priv->ptp.info = ravb_ptp_info;
@@ -344,7 +345,15 @@ void ravb_ptp_init(struct net_device *ndev, struct platform_device *pdev)
 	ravb_modify(ndev, GCCR, GCCR_TCSS, GCCR_TCSS_ADJGPTP);
 	spin_unlock_irqrestore(&priv->lock, flags);
 
-	priv->ptp.clock = ptp_clock_register(&priv->ptp.info, &pdev->dev);
+	clock = ptp_clock_register(&priv->ptp.info, &pdev->dev);
+	if (IS_ERR(clock)) {
+		netdev_err(ndev, "failed to register PTP clock: %pe\n", clock);
+		clock = NULL;
+	}
+
+	priv->ptp.clock = clock;
+	if (clock)
+		WRITE_ONCE(priv->ptp.phc_index, ptp_clock_index(clock));
 }
 
 void ravb_ptp_stop(struct net_device *ndev)
@@ -354,5 +363,7 @@ void ravb_ptp_stop(struct net_device *ndev)
 	ravb_write(ndev, 0, GIC);
 	ravb_write(ndev, 0, GIS);
 
-	ptp_clock_unregister(priv->ptp.clock);
+	WRITE_ONCE(priv->ptp.phc_index, -1);
+	if (priv->ptp.clock)
+		ptp_clock_unregister(priv->ptp.clock);
 }
-- 
2.53.0