Merge branch 'net-mscc-ocelot-fix-missing-lock-in-ocelot_port_xmit'

Ziyi Guo says:

====================
net: mscc: ocelot: fix missing lock in ocelot_port_xmit()

ocelot_port_xmit() calls ocelot_can_inject() and
ocelot_port_inject_frame() without holding the injection group lock.
Both functions contain lockdep_assert_held() for the injection lock,
and the correct caller felix_port_deferred_xmit() properly acquires
the lock using ocelot_lock_inj_grp() before calling these functions.

this v3 splits the fix into a 3-patch series to separate
refactoring from the behavioral change:

  1/3: Extract the PTP timestamp handling into an ocelot_xmit_timestamp()
       helper so the logic isn't duplicated when the function is split.

  2/3: Split ocelot_port_xmit() into ocelot_port_xmit_fdma() and
       ocelot_port_xmit_inj(), keeping the FDMA and register injection
       code paths fully separate.

  3/3: Add ocelot_lock_inj_grp()/ocelot_unlock_inj_grp() in
       ocelot_port_xmit_inj() to fix the missing lock protection.

Patches 1-2 are pure refactors with no behavioral change.
Patch 3 is the actual bug fix.
====================

Link: https://patch.msgid.link/20260208225602.1339325-1-n7l8m4@u.northwestern.edu
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 56 insertions, 19 deletions

diff --git a/drivers/net/ethernet/mscc/ocelot_net.c b/drivers/net/ethernet/mscc/ocelot_net.c
index 469784d3a1a6..1b8269320464 100644
--- a/drivers/net/ethernet/mscc/ocelot_net.c
+++ b/drivers/net/ethernet/mscc/ocelot_net.c
@@ -551,44 +551,81 @@ static int ocelot_port_stop(struct net_device *dev)
 	return 0;
 }
 
-static netdev_tx_t ocelot_port_xmit(struct sk_buff *skb, struct net_device *dev)
+static bool ocelot_xmit_timestamp(struct ocelot *ocelot, int port,
+				  struct sk_buff *skb, u32 *rew_op)
 {
-	struct ocelot_port_private *priv = netdev_priv(dev);
-	struct ocelot_port *ocelot_port = &priv->port;
-	struct ocelot *ocelot = ocelot_port->ocelot;
-	int port = priv->port.index;
-	u32 rew_op = 0;
-
-	if (!static_branch_unlikely(&ocelot_fdma_enabled) &&
-	    !ocelot_can_inject(ocelot, 0))
-		return NETDEV_TX_BUSY;
-
-	/* Check if timestamping is needed */
 	if (ocelot->ptp && (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)) {
 		struct sk_buff *clone = NULL;
 
 		if (ocelot_port_txtstamp_request(ocelot, port, skb, &clone)) {
 			kfree_skb(skb);
-			return NETDEV_TX_OK;
+			return false;
 		}
 
 		if (clone)
 			OCELOT_SKB_CB(skb)->clone = clone;
 
-		rew_op = ocelot_ptp_rew_op(skb);
+		*rew_op = ocelot_ptp_rew_op(skb);
 	}
 
-	if (static_branch_unlikely(&ocelot_fdma_enabled)) {
-		ocelot_fdma_inject_frame(ocelot, port, rew_op, skb, dev);
-	} else {
-		ocelot_port_inject_frame(ocelot, port, 0, rew_op, skb);
+	return true;
+}
+
+static netdev_tx_t ocelot_port_xmit_fdma(struct sk_buff *skb,
+					 struct net_device *dev)
+{
+	struct ocelot_port_private *priv = netdev_priv(dev);
+	struct ocelot_port *ocelot_port = &priv->port;
+	struct ocelot *ocelot = ocelot_port->ocelot;
+	int port = priv->port.index;
+	u32 rew_op = 0;
+
+	if (!ocelot_xmit_timestamp(ocelot, port, skb, &rew_op))
+		return NETDEV_TX_OK;
+
+	ocelot_fdma_inject_frame(ocelot, port, rew_op, skb, dev);
+
+	return NETDEV_TX_OK;
+}
 
-		consume_skb(skb);
+static netdev_tx_t ocelot_port_xmit_inj(struct sk_buff *skb,
+					struct net_device *dev)
+{
+	struct ocelot_port_private *priv = netdev_priv(dev);
+	struct ocelot_port *ocelot_port = &priv->port;
+	struct ocelot *ocelot = ocelot_port->ocelot;
+	int port = priv->port.index;
+	u32 rew_op = 0;
+
+	ocelot_lock_inj_grp(ocelot, 0);
+
+	if (!ocelot_can_inject(ocelot, 0)) {
+		ocelot_unlock_inj_grp(ocelot, 0);
+		return NETDEV_TX_BUSY;
 	}
 
+	if (!ocelot_xmit_timestamp(ocelot, port, skb, &rew_op)) {
+		ocelot_unlock_inj_grp(ocelot, 0);
+		return NETDEV_TX_OK;
+	}
+
+	ocelot_port_inject_frame(ocelot, port, 0, rew_op, skb);
+
+	ocelot_unlock_inj_grp(ocelot, 0);
+
+	consume_skb(skb);
+
 	return NETDEV_TX_OK;
 }
 
+static netdev_tx_t ocelot_port_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	if (static_branch_unlikely(&ocelot_fdma_enabled))
+		return ocelot_port_xmit_fdma(skb, dev);
+
+	return ocelot_port_xmit_inj(skb, dev);
+}
+
 enum ocelot_action_type {
 	OCELOT_MACT_LEARN,
 	OCELOT_MACT_FORGET,