FAILED: patch "[PATCH] net: ravb: avoid dereferencing an invalid PTP clock" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 1f77af0aaf277413ff32f6ff8c2c4282bd64c897
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026090322-boss-emu-7014@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1f77af0aaf277413ff32f6ff8c2c4282bd64c897 Mon Sep 17 00:00:00 2001
From: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
Date: Tue, 11 Aug 2026 18:37:32 +0800
Subject: [PATCH] net: ravb: avoid dereferencing an invalid PTP clock

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>

diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index 5e56ec9b1013..2a4fcb12a63c 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -1028,6 +1028,7 @@ 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 5f88733094d0..db0229e00849 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1779,7 +1779,7 @@ 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;
@@ -2953,6 +2953,7 @@ 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;
 	if (info->nc_queues) {
diff --git a/drivers/net/ethernet/renesas/ravb_ptp.c b/drivers/net/ethernet/renesas/ravb_ptp.c
index 226c6c0ab945..cbec7c057d71 100644
--- a/drivers/net/ethernet/renesas/ravb_ptp.c
+++ b/drivers/net/ethernet/renesas/ravb_ptp.c
@@ -315,6 +315,7 @@ 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;
@@ -327,7 +328,15 @@ 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)
@@ -337,5 +346,7 @@ 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);
 }