From: Eric Dumazet Date: Thu, 4 Jun 2026 14:13:37 +0000 (+0000) Subject: bridge: provide lockless access to p->path_cost X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=f236240c9beba15ea6fc6580c6cc63c40725d3ff;p=thirdparty%2Flinux.git bridge: provide lockless access to p->path_cost Add READ_ONCE()/WRITE_ONCE() annotations around p->path_cost. This is needed at least for sysfs show_path_cost(), BRCTL_GET_PORT_INFO and upcoming RTNL avoidance in "ip link" dumps (cf br_port_fill_attrs()). Signed-off-by: Eric Dumazet Acked-by: Nikolay Aleksandrov Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260604141343.2124500-6-edumazet@google.com Signed-off-by: Jakub Kicinski --- diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c index 630ca7ac962a..463c3c7083dc 100644 --- a/net/bridge/br_if.c +++ b/net/bridge/br_if.c @@ -78,7 +78,7 @@ void br_port_carrier_check(struct net_bridge_port *p, bool *notified) if (!test_bit(BR_ADMIN_COST_BIT, &p->flags) && netif_running(dev) && netif_oper_up(dev)) - p->path_cost = port_cost(dev); + WRITE_ONCE(p->path_cost, port_cost(dev)); *notified = false; if (!netif_running(br->dev)) diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c index 766c43b327af..07cfcb821e27 100644 --- a/net/bridge/br_ioctl.c +++ b/net/bridge/br_ioctl.c @@ -259,7 +259,7 @@ int br_dev_siocdevprivate(struct net_device *dev, struct ifreq *rq, memcpy(&p.designated_bridge, &pt->designated_bridge, 8); p.port_id = pt->port_id; p.designated_port = pt->designated_port; - p.path_cost = pt->path_cost; + p.path_cost = READ_ONCE(pt->path_cost); p.designated_cost = pt->designated_cost; p.state = pt->state; p.top_change_ack = pt->topology_change_ack; diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c index a104b25c871d..08718ebe282a 100644 --- a/net/bridge/br_netlink.c +++ b/net/bridge/br_netlink.c @@ -240,7 +240,7 @@ static int br_port_fill_attrs(struct sk_buff *skb, if (nla_put_u8(skb, IFLA_BRPORT_STATE, p->state) || nla_put_u16(skb, IFLA_BRPORT_PRIORITY, p->priority) || - nla_put_u32(skb, IFLA_BRPORT_COST, p->path_cost) || + nla_put_u32(skb, IFLA_BRPORT_COST, READ_ONCE(p->path_cost)) || nla_put_u8(skb, IFLA_BRPORT_MODE, mode) || nla_put_u8(skb, IFLA_BRPORT_GUARD, !!(p->flags & BR_BPDU_GUARD)) || nla_put_u8(skb, IFLA_BRPORT_PROTECT, diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c index 024210f95468..2d9d0823aa56 100644 --- a/net/bridge/br_stp.c +++ b/net/bridge/br_stp.c @@ -102,8 +102,9 @@ struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no) static int br_should_become_root_port(const struct net_bridge_port *p, u16 root_port) { - struct net_bridge *br; + u32 p_path_cost, rp_path_cost; struct net_bridge_port *rp; + struct net_bridge *br; int t; br = p->br; @@ -125,11 +126,14 @@ static int br_should_become_root_port(const struct net_bridge_port *p, else if (t > 0) return 0; - if (p->designated_cost + p->path_cost < - rp->designated_cost + rp->path_cost) + p_path_cost = READ_ONCE(p->path_cost); + rp_path_cost = READ_ONCE(rp->path_cost); + + if (p->designated_cost + p_path_cost < + rp->designated_cost + rp_path_cost) return 1; - else if (p->designated_cost + p->path_cost > - rp->designated_cost + rp->path_cost) + else if (p->designated_cost + p_path_cost > + rp->designated_cost + rp_path_cost) return 0; t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8); @@ -187,7 +191,8 @@ static void br_root_selection(struct net_bridge *br) } else { p = br_get_port(br, root_port); br->designated_root = p->designated_root; - br->root_path_cost = p->designated_cost + p->path_cost; + br->root_path_cost = p->designated_cost + + READ_ONCE(p->path_cost); } } diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c index b29dc97b9ad8..e5d43492d2dc 100644 --- a/net/bridge/br_stp_if.c +++ b/net/bridge/br_stp_if.c @@ -341,7 +341,7 @@ int br_stp_set_path_cost(struct net_bridge_port *p, unsigned long path_cost) return -ERANGE; set_bit(BR_ADMIN_COST_BIT, &p->flags); - p->path_cost = path_cost; + WRITE_ONCE(p->path_cost, path_cost); br_configuration_update(p->br); br_port_state_selection(p->br); return 0; diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c index d6df81fa0d13..23574476d7f7 100644 --- a/net/bridge/br_sysfs_if.c +++ b/net/bridge/br_sysfs_if.c @@ -83,7 +83,7 @@ static int store_flag(struct net_bridge_port *p, unsigned long v, static ssize_t show_path_cost(struct net_bridge_port *p, char *buf) { - return sysfs_emit(buf, "%d\n", p->path_cost); + return sysfs_emit(buf, "%d\n", READ_ONCE(p->path_cost)); } static int store_path_cost(struct net_bridge_port *p, unsigned long v)