netdev - [PATCH net] net: bonding: fix possible peer notify event loss or dup issue

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Message-Id: <20251021050933.46412-1-tonghao@bamaicloud.com>
Date: Tue, 21 Oct 2025 13:09:33 +0800
From: Tonghao Zhang <tonghao@...aicloud.com>
To: netdev@...r.kernel.org
Cc: Tonghao Zhang <tonghao@...aicloud.com>,
	Jay Vosburgh <jv@...sburgh.net>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Hangbin Liu <liuhangbin@...il.com>,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	Vincent Bernat <vincent@...nat.ch>,
	stable@...r.kernel.org
Subject: [PATCH net] net: bonding: fix possible peer notify event loss or dup issue

If the send_peer_notif counter and the peer event notify are not synchronized.
It may cause problems such as the loss or dup of peer notify event.

Before this patch:
- If should_notify_peers is true and the lock for send_peer_notif-- fails, peer
  event may be sent again in next mii_monitor loop, because should_notify_peers
  is still true.
- If should_notify_peers is true and the lock for send_peer_notif-- succeeded,
  but the lock for peer event fails, the peer event will be lost.

This patch locks the RTNL for send_peer_notif, events, and commit simultaneously.

Fixes: 07a4ddec3ce9 ("bonding: add an option to specify a delay between peer notifications")
Cc: Jay Vosburgh <jv@...sburgh.net>
Cc: Andrew Lunn <andrew+netdev@...n.ch>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: Hangbin Liu <liuhangbin@...il.com>
Cc: Nikolay Aleksandrov <razor@...ckwall.org>
Cc: Vincent Bernat <vincent@...nat.ch>
Cc: <stable@...r.kernel.org>
Signed-off-by: Tonghao Zhang <tonghao@...aicloud.com>

---
 drivers/net/bonding/bond_main.c | 40 +++++++++++++++------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 5791c3e39baa..52b7ac8ddfbc 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2971,7 +2971,7 @@ static void bond_mii_monitor(struct work_struct *work)
 {
 	struct bonding *bond = container_of(work, struct bonding,
 					    mii_work.work);
-	bool should_notify_peers = false;
+	bool should_notify_peers;
 	bool commit;
 	unsigned long delay;
 	struct slave *slave;
@@ -2983,30 +2983,33 @@ static void bond_mii_monitor(struct work_struct *work)
 		goto re_arm;
 
 	rcu_read_lock();
+
 	should_notify_peers = bond_should_notify_peers(bond);
 	commit = !!bond_miimon_inspect(bond);
-	if (bond->send_peer_notif) {
-		rcu_read_unlock();
-		if (rtnl_trylock()) {
-			bond->send_peer_notif--;
-			rtnl_unlock();
-		}
-	} else {
-		rcu_read_unlock();
-	}
 
-	if (commit) {
+	rcu_read_unlock();
+
+	if (commit || bond->send_peer_notif) {
 		/* Race avoidance with bond_close cancel of workqueue */
 		if (!rtnl_trylock()) {
 			delay = 1;
-			should_notify_peers = false;
 			goto re_arm;
 		}
 
-		bond_for_each_slave(bond, slave, iter) {
-			bond_commit_link_state(slave, BOND_SLAVE_NOTIFY_LATER);
+		if (commit) {
+			bond_for_each_slave(bond, slave, iter) {
+				bond_commit_link_state(slave,
+						       BOND_SLAVE_NOTIFY_LATER);
+			}
+			bond_miimon_commit(bond);
+		}
+
+		if (bond->send_peer_notif) {
+			bond->send_peer_notif--;
+			if (should_notify_peers)
+				call_netdevice_notifiers(NETDEV_NOTIFY_PEERS,
+							 bond->dev);
 		}
-		bond_miimon_commit(bond);
 
 		rtnl_unlock();	/* might sleep, hold no other locks */
 	}
@@ -3014,13 +3017,6 @@ static void bond_mii_monitor(struct work_struct *work)
 re_arm:
 	if (bond->params.miimon)
 		queue_delayed_work(bond->wq, &bond->mii_work, delay);
-
-	if (should_notify_peers) {
-		if (!rtnl_trylock())
-			return;
-		call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, bond->dev);
-		rtnl_unlock();
-	}
 }
 
 static int bond_upper_dev_walk(struct net_device *upper,
-- 
2.34.1