From: Eric Dumazet <edumazet@google.com>
Date: Thu, 4 Jun 2026 14:13:41 +0000 (+0000)
Subject: bridge: provide lockless access to p->port_id
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6d39b5d080094f2224284fd54a86d8c79ef14e27;p=thirdparty%2Flinux.git

bridge: provide lockless access to p->port_id

sysfs show_port_id() and BRCTL_GET_PORT_INFO need this.

This will be needed for upcoming RTNL avoidance in "ip link"
dumps (cf br_port_fill_attrs()).

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20260604141343.2124500-10-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c
index 2be802991f70a..a017374c6e659 100644
--- a/net/bridge/br_ioctl.c
+++ b/net/bridge/br_ioctl.c
@@ -257,7 +257,7 @@ int br_dev_siocdevprivate(struct net_device *dev, struct ifreq *rq,
 		memset(&p, 0, sizeof(struct __port_info));
 		memcpy(&p.designated_root, &pt->designated_root, 8);
 		memcpy(&p.designated_bridge, &pt->designated_bridge, 8);
-		p.port_id = pt->port_id;
+		p.port_id = READ_ONCE(pt->port_id);
 		p.designated_port = READ_ONCE(pt->designated_port);
 		p.path_cost = READ_ONCE(pt->path_cost);
 		p.designated_cost = READ_ONCE(pt->designated_cost);
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index fc25c6b6cc971..f8266a7a9e2b9 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -267,7 +267,7 @@ static int br_port_fill_attrs(struct sk_buff *skb,
 			READ_ONCE(p->designated_port)) ||
 	    nla_put_u16(skb, IFLA_BRPORT_DESIGNATED_COST,
 			READ_ONCE(p->designated_cost)) ||
-	    nla_put_u16(skb, IFLA_BRPORT_ID, p->port_id) ||
+	    nla_put_u16(skb, IFLA_BRPORT_ID, READ_ONCE(p->port_id)) ||
 	    nla_put_u16(skb, IFLA_BRPORT_NO, p->port_no) ||
 	    nla_put_u8(skb, IFLA_BRPORT_TOPOLOGY_CHANGE_ACK,
 		       p->topology_change_ack) ||
diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index 3524bb7e87f05..8a418f6af423c 100644
--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -34,7 +34,7 @@ void br_init_port(struct net_bridge_port *p)
 {
 	int err;
 
-	p->port_id = br_make_port_id(p->priority, p->port_no);
+	WRITE_ONCE(p->port_id, br_make_port_id(p->priority, p->port_no));
 	br_become_designated_port(p);
 	br_set_state(p, BR_STATE_BLOCKING);
 	p->topology_change_ack = 0;
@@ -322,7 +322,7 @@ int br_stp_set_port_priority(struct net_bridge_port *p, unsigned long newprio)
 	if (br_is_designated_port(p))
 		WRITE_ONCE(p->designated_port, new_port_id);
 
-	p->port_id = new_port_id;
+	WRITE_ONCE(p->port_id, new_port_id);
 	WRITE_ONCE(p->priority, newprio);
 	if (!memcmp(&p->br->bridge_id, &p->designated_bridge, 8) &&
 	    p->port_id < p->designated_port) {
diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
index 3f666d4fef423..1cc474ed0fdc0 100644
--- a/net/bridge/br_sysfs_if.c
+++ b/net/bridge/br_sysfs_if.c
@@ -141,7 +141,7 @@ static BRPORT_ATTR(designated_cost, 0444, show_designated_cost, NULL);
 
 static ssize_t show_port_id(struct net_bridge_port *p, char *buf)
 {
-	return sysfs_emit(buf, "0x%x\n", p->port_id);
+	return sysfs_emit(buf, "0x%x\n", READ_ONCE(p->port_id));
 }
 static BRPORT_ATTR(port_id, 0444, show_port_id, NULL);