macvlan: annotate data-races around port->bc_queue_len_used

[ Upstream commit 1ef5789 ]

port->bc_queue_len_used is read and written locklessly,
add READ_ONCE()/WRITE_ONCE() annotations.

While WRITE_ONCE() in macvlan_fill_info() is not yet needed,
it is a prereq for future RTNL avoidance.

Fixes: d4bff72 ("macvlan: Support for high multicast packet rate")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260401103809.3038139-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: edumazet

drivers/net/macvlan.c

@@ -351,6 +351,7 @@ static void macvlan_broadcast_enqueue(struct macvlan_port *port,
 				      const struct macvlan_dev *src,
 				      struct sk_buff *skb)
 {
+	u32 bc_queue_len_used = READ_ONCE(port->bc_queue_len_used);
 	struct sk_buff *nskb;
 	int err = -ENOMEM;
 
@@ -361,7 +362,7 @@ static void macvlan_broadcast_enqueue(struct macvlan_port *port,
 	MACVLAN_SKB_CB(nskb)->src = src;
 
 	spin_lock(&port->bc_queue.lock);
-	if (skb_queue_len(&port->bc_queue) < port->bc_queue_len_used) {
+	if (skb_queue_len(&port->bc_queue) < bc_queue_len_used) {
 		if (src)
 			dev_hold(src->dev);
 		__skb_queue_tail(&port->bc_queue, nskb);
@@ -1723,7 +1724,8 @@ static int macvlan_fill_info(struct sk_buff *skb,
 	}
 	if (nla_put_u32(skb, IFLA_MACVLAN_BC_QUEUE_LEN, vlan->bc_queue_len_req))
 		goto nla_put_failure;
-	if (nla_put_u32(skb, IFLA_MACVLAN_BC_QUEUE_LEN_USED, port->bc_queue_len_used))
+	if (nla_put_u32(skb, IFLA_MACVLAN_BC_QUEUE_LEN_USED,
+			READ_ONCE(port->bc_queue_len_used)))
 		goto nla_put_failure;
 	if (port->bc_cutoff != 1 &&
 	    nla_put_s32(skb, IFLA_MACVLAN_BC_CUTOFF, port->bc_cutoff))
@@ -1783,7 +1785,7 @@ static void update_port_bc_queue_len(struct macvlan_port *port)
 		if (vlan->bc_queue_len_req > max_bc_queue_len_req)
 			max_bc_queue_len_req = vlan->bc_queue_len_req;
 	}
-	port->bc_queue_len_used = max_bc_queue_len_req;
+	WRITE_ONCE(port->bc_queue_len_used, max_bc_queue_len_req);
 }
 
 static int macvlan_device_event(struct notifier_block *unused,