[PATCH v2 net] bonding: no longer rely on RTNL in bond_fill_info()
From: Eric Dumazet <edumazet@google.com>
Date: 2026-06-08 13:50:53
Subsystem:
bonding driver, networking drivers, networking [general], the rest · Maintainers:
Jay Vosburgh, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Add READ_ONCE()/WRITE_ONCE() annotations on port->is_enabled. While this field is written under bond->mode_lock protection, is is read without this lock being held. Change bond_fill_info() to acquire RCU and use READ_ONCE() to read bond->params fields that can be updated concurrently from sysfs/procfs/rtnetlink. Add const qualifiers to bond_uses_primary(), __agg_active_ports(), bond_option_active_slave_get_rcu(), bond_3ad_get_active_agg_info(), __bond_3ad_get_active_agg_info() helpers. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Jay Vosburgh <jv@jvosburgh.net> Cc: Andrew Lunn <andrew+netdev@lunn.ch> --- v2: addressed sashiko.dev feedback. drivers/net/bonding/bond_3ad.c | 18 ++--- drivers/net/bonding/bond_netlink.c | 107 ++++++++++++++++------------- drivers/net/bonding/bond_options.c | 6 +- include/net/bond_3ad.h | 4 +- include/net/bonding.h | 8 +-- 5 files changed, 78 insertions(+), 65 deletions(-)
diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index 985ef66dc3331e89458c9951a222d140c2275fb9..090b13b1e83ae31c9dbca6ed92a7a62dfa17ed80 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c@@ -745,14 +745,14 @@ static void __set_agg_ports_ready(struct aggregator *aggregator, int val) } } -static int __agg_active_ports(struct aggregator *agg) +static int __agg_active_ports(const struct aggregator *agg) { - struct port *port; + const struct port *port; int active = 0; for (port = agg->lag_ports; port; port = port->next_port_in_aggregator) { - if (port->is_enabled) + if (READ_ONCE(port->is_enabled)) active++; }
@@ -2782,11 +2782,11 @@ void bond_3ad_handle_link_change(struct slave *slave, char link) * some of he adaptors(ce1000.lan) report. */ if (link == BOND_LINK_UP) { - port->is_enabled = true; + WRITE_ONCE(port->is_enabled, true); ad_update_actor_keys(port, false); } else { /* link has failed */ - port->is_enabled = false; + WRITE_ONCE(port->is_enabled, false); ad_update_actor_keys(port, true); } agg = __get_first_agg(port);
@@ -2857,13 +2857,13 @@ int bond_3ad_set_carrier(struct bonding *bond) * Returns: 0 on success * < 0 on error */ -int __bond_3ad_get_active_agg_info(struct bonding *bond, +int __bond_3ad_get_active_agg_info(const struct bonding *bond, struct ad_info *ad_info) { - struct aggregator *aggregator = NULL, *tmp; + const struct aggregator *aggregator = NULL, *tmp; + const struct port *port; struct list_head *iter; struct slave *slave; - struct port *port; bond_for_each_slave_rcu(bond, slave, iter) { port = &(SLAVE_AD_INFO(slave)->port);
@@ -2886,7 +2886,7 @@ int __bond_3ad_get_active_agg_info(struct bonding *bond, return 0; } -int bond_3ad_get_active_agg_info(struct bonding *bond, struct ad_info *ad_info) +int bond_3ad_get_active_agg_info(const struct bonding *bond, struct ad_info *ad_info) { int ret;
diff --git a/drivers/net/bonding/bond_netlink.c b/drivers/net/bonding/bond_netlink.c
index 90365d3f7ebff7f762b4cb10303a3dd3fdd49cc6..aa1725e6a37762b0386481eb012b2f6b90925427 100644
--- a/drivers/net/bonding/bond_netlink.c
+++ b/drivers/net/bonding/bond_netlink.c@@ -674,53 +674,58 @@ static size_t bond_get_size(const struct net_device *bond_dev) 0; } -static int bond_option_active_slave_get_ifindex(struct bonding *bond) +static int bond_option_active_slave_get_ifindex_rcu(const struct bonding *bond) { - const struct net_device *slave; - int ifindex; + const struct net_device *dev = NULL; + const struct slave *slave; - rcu_read_lock(); - slave = bond_option_active_slave_get_rcu(bond); - ifindex = slave ? slave->ifindex : 0; - rcu_read_unlock(); - return ifindex; + slave = rcu_dereference(bond->curr_active_slave); + if (slave) + dev = slave->dev; + return dev ? dev->ifindex : 0; } static int bond_fill_info(struct sk_buff *skb, const struct net_device *bond_dev) { - struct bonding *bond = netdev_priv(bond_dev); - unsigned int packets_per_slave; - int ifindex, i, targets_added; + const struct bonding *bond = netdev_priv(bond_dev); + int i, targets_added, miimon, mode; + const struct slave *primary; struct nlattr *targets; - struct slave *primary; - if (nla_put_u8(skb, IFLA_BOND_MODE, BOND_MODE(bond))) + rcu_read_lock(); + mode = READ_ONCE(bond->params.mode); + if (nla_put_u8(skb, IFLA_BOND_MODE, mode)) goto nla_put_failure; - ifindex = bond_option_active_slave_get_ifindex(bond); - if (ifindex && nla_put_u32(skb, IFLA_BOND_ACTIVE_SLAVE, ifindex)) - goto nla_put_failure; + if (bond_mode_uses_primary(mode)) { + int ifindex = bond_option_active_slave_get_ifindex_rcu(bond); + + if (ifindex && nla_put_u32(skb, IFLA_BOND_ACTIVE_SLAVE, ifindex)) + goto nla_put_failure; + } - if (nla_put_u32(skb, IFLA_BOND_MIIMON, bond->params.miimon)) + miimon = READ_ONCE(bond->params.miimon); + if (nla_put_u32(skb, IFLA_BOND_MIIMON, miimon)) goto nla_put_failure; if (nla_put_u32(skb, IFLA_BOND_UPDELAY, - bond->params.updelay * bond->params.miimon)) + READ_ONCE(bond->params.updelay) * miimon)) goto nla_put_failure; if (nla_put_u32(skb, IFLA_BOND_DOWNDELAY, - bond->params.downdelay * bond->params.miimon)) + READ_ONCE(bond->params.downdelay) * miimon)) goto nla_put_failure; if (nla_put_u32(skb, IFLA_BOND_PEER_NOTIF_DELAY, - bond->params.peer_notif_delay * bond->params.miimon)) + READ_ONCE(bond->params.peer_notif_delay) * miimon)) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_USE_CARRIER, 1)) goto nla_put_failure; - if (nla_put_u32(skb, IFLA_BOND_ARP_INTERVAL, bond->params.arp_interval)) + if (nla_put_u32(skb, IFLA_BOND_ARP_INTERVAL, + READ_ONCE(bond->params.arp_interval))) goto nla_put_failure; targets = nla_nest_start_noflag(skb, IFLA_BOND_ARP_IP_TARGET);
@@ -729,8 +734,10 @@ static int bond_fill_info(struct sk_buff *skb, targets_added = 0; for (i = 0; i < BOND_MAX_ARP_TARGETS; i++) { - if (bond->params.arp_targets[i]) { - if (nla_put_be32(skb, i, bond->params.arp_targets[i])) + __be32 t = READ_ONCE(bond->params.arp_targets[i]); + + if (t) { + if (nla_put_be32(skb, i, t)) goto nla_put_failure; targets_added = 1; }
@@ -741,11 +748,12 @@ static int bond_fill_info(struct sk_buff *skb, else nla_nest_cancel(skb, targets); - if (nla_put_u32(skb, IFLA_BOND_ARP_VALIDATE, bond->params.arp_validate)) + if (nla_put_u32(skb, IFLA_BOND_ARP_VALIDATE, + READ_ONCE(bond->params.arp_validate))) goto nla_put_failure; if (nla_put_u32(skb, IFLA_BOND_ARP_ALL_TARGETS, - bond->params.arp_all_targets)) + READ_ONCE(bond->params.arp_all_targets))) goto nla_put_failure; #if IS_ENABLED(CONFIG_IPV6)
@@ -755,6 +763,9 @@ static int bond_fill_info(struct sk_buff *skb, targets_added = 0; for (i = 0; i < BOND_MAX_NS_TARGETS; i++) { + /* Note: IPv6 addresses can not be read in an atomic READ_ONCE() yet. + * We accept this minor race for the moment. + */ if (!ipv6_addr_any(&bond->params.ns_targets[i])) { if (nla_put_in6_addr(skb, i, &bond->params.ns_targets[i])) goto nla_put_failure;
@@ -768,93 +779,93 @@ static int bond_fill_info(struct sk_buff *skb, nla_nest_cancel(skb, targets); #endif - primary = rtnl_dereference(bond->primary_slave); + primary = rcu_dereference(bond->primary_slave); if (primary && nla_put_u32(skb, IFLA_BOND_PRIMARY, primary->dev->ifindex)) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_PRIMARY_RESELECT, - bond->params.primary_reselect)) + READ_ONCE(bond->params.primary_reselect))) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_FAIL_OVER_MAC, - bond->params.fail_over_mac)) + READ_ONCE(bond->params.fail_over_mac))) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_XMIT_HASH_POLICY, - bond->params.xmit_policy)) + READ_ONCE(bond->params.xmit_policy))) goto nla_put_failure; if (nla_put_u32(skb, IFLA_BOND_RESEND_IGMP, - bond->params.resend_igmp)) + READ_ONCE(bond->params.resend_igmp))) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_NUM_PEER_NOTIF, - bond->params.num_peer_notif)) + READ_ONCE(bond->params.num_peer_notif))) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_ALL_SLAVES_ACTIVE, - bond->params.all_slaves_active)) + READ_ONCE(bond->params.all_slaves_active))) goto nla_put_failure; if (nla_put_u32(skb, IFLA_BOND_MIN_LINKS, - bond->params.min_links)) + READ_ONCE(bond->params.min_links))) goto nla_put_failure; if (nla_put_u32(skb, IFLA_BOND_LP_INTERVAL, - bond->params.lp_interval)) + READ_ONCE(bond->params.lp_interval))) goto nla_put_failure; - packets_per_slave = bond->params.packets_per_slave; if (nla_put_u32(skb, IFLA_BOND_PACKETS_PER_SLAVE, - packets_per_slave)) + READ_ONCE(bond->params.packets_per_slave))) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_AD_LACP_ACTIVE, - bond->params.lacp_active)) + READ_ONCE(bond->params.lacp_active))) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_AD_LACP_RATE, - bond->params.lacp_fast)) + READ_ONCE(bond->params.lacp_fast))) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_AD_SELECT, - bond->params.ad_select)) + READ_ONCE(bond->params.ad_select))) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_TLB_DYNAMIC_LB, - bond->params.tlb_dynamic_lb)) + READ_ONCE(bond->params.tlb_dynamic_lb))) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_MISSED_MAX, - bond->params.missed_max)) + READ_ONCE(bond->params.missed_max))) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_COUPLED_CONTROL, - bond->params.coupled_control)) + READ_ONCE(bond->params.coupled_control))) goto nla_put_failure; if (nla_put_u8(skb, IFLA_BOND_BROADCAST_NEIGH, - bond->params.broadcast_neighbor)) + READ_ONCE(bond->params.broadcast_neighbor))) goto nla_put_failure; - if (BOND_MODE(bond) == BOND_MODE_8023AD) { + if (mode == BOND_MODE_8023AD) { struct ad_info info; if (capable(CAP_NET_ADMIN)) { if (nla_put_u16(skb, IFLA_BOND_AD_ACTOR_SYS_PRIO, - bond->params.ad_actor_sys_prio)) + READ_ONCE(bond->params.ad_actor_sys_prio))) goto nla_put_failure; if (nla_put_u16(skb, IFLA_BOND_AD_USER_PORT_KEY, - bond->params.ad_user_port_key)) + READ_ONCE(bond->params.ad_user_port_key))) goto nla_put_failure; + /* Small race here, this is a minor trade off. */ if (nla_put(skb, IFLA_BOND_AD_ACTOR_SYSTEM, ETH_ALEN, &bond->params.ad_actor_system)) goto nla_put_failure; } - if (!bond_3ad_get_active_agg_info(bond, &info)) { + if (!__bond_3ad_get_active_agg_info(bond, &info)) { struct nlattr *nest; nest = nla_nest_start_noflag(skb, IFLA_BOND_AD_INFO);
@@ -882,9 +893,11 @@ static int bond_fill_info(struct sk_buff *skb, } } + rcu_read_unlock(); return 0; nla_put_failure: + rcu_read_unlock(); return -EMSGSIZE; }
diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
index 5095ac3dad2cd924ff548343c7c1afe3e57e3065..a70407b5fb2bbfebe49c9f242f1be81933a6a912 100644
--- a/drivers/net/bonding/bond_options.c
+++ b/drivers/net/bonding/bond_options.c@@ -918,14 +918,14 @@ static int bond_option_mode_set(struct bonding *bond, /* don't cache arp_validate between modes */ WRITE_ONCE(bond->params.arp_validate, BOND_ARP_VALIDATE_NONE); - bond->params.mode = newval->value; + WRITE_ONCE(bond->params.mode, newval->value); /* When changing mode, the bond device is down, we may reduce * the bond_bcast_neigh_enabled in bond_close() if broadcast_neighbor * enabled in 8023ad mode. Therefore, only clear broadcast_neighbor * to 0. */ - bond->params.broadcast_neighbor = 0; + WRITE_ONCE(bond->params.broadcast_neighbor, 0); if (bond->dev->reg_state == NETREG_REGISTERED) { bool update = false;
@@ -1900,7 +1900,7 @@ static int bond_option_broadcast_neigh_set(struct bonding *bond, if (bond->params.broadcast_neighbor == newval->value) return 0; - bond->params.broadcast_neighbor = newval->value; + WRITE_ONCE(bond->params.broadcast_neighbor, newval->value); if (bond->dev->flags & IFF_UP) { if (bond->params.broadcast_neighbor) static_branch_inc(&bond_bcast_neigh_enabled);
diff --git a/include/net/bond_3ad.h b/include/net/bond_3ad.h
index 05572c19e14b7ae97d497cc9c5d97d4314eab295..ef667dff297294dc78d98701aae10c31ef09df3f 100644
--- a/include/net/bond_3ad.h
+++ b/include/net/bond_3ad.h@@ -302,8 +302,8 @@ void bond_3ad_state_machine_handler(struct work_struct *); void bond_3ad_initiate_agg_selection(struct bonding *bond, int timeout); void bond_3ad_adapter_speed_duplex_changed(struct slave *slave); void bond_3ad_handle_link_change(struct slave *slave, char link); -int bond_3ad_get_active_agg_info(struct bonding *bond, struct ad_info *ad_info); -int __bond_3ad_get_active_agg_info(struct bonding *bond, +int bond_3ad_get_active_agg_info(const struct bonding *bond, struct ad_info *ad_info); +int __bond_3ad_get_active_agg_info(const struct bonding *bond, struct ad_info *ad_info); int bond_3ad_lacpdu_recv(const struct sk_buff *skb, struct bonding *bond, struct slave *slave);
diff --git a/include/net/bonding.h b/include/net/bonding.h
index edd1942dcd736d3601e799dfbc9aeb8da0835902..f464ff163357637661500a6172902e5bb7401031 100644
--- a/include/net/bonding.h
+++ b/include/net/bonding.h@@ -344,14 +344,14 @@ static inline bool bond_mode_uses_primary(int mode) mode == BOND_MODE_ALB; } -static inline bool bond_uses_primary(struct bonding *bond) +static inline bool bond_uses_primary(const struct bonding *bond) { return bond_mode_uses_primary(BOND_MODE(bond)); } -static inline struct net_device *bond_option_active_slave_get_rcu(struct bonding *bond) +static inline struct net_device *bond_option_active_slave_get_rcu(const struct bonding *bond) { - struct slave *slave = rcu_dereference_rtnl(bond->curr_active_slave); + const struct slave *slave = rcu_dereference_rtnl(bond->curr_active_slave); return bond_uses_primary(bond) && slave ? slave->dev : NULL; }
@@ -702,7 +702,7 @@ void bond_setup(struct net_device *bond_dev); unsigned int bond_get_num_tx_queues(void); int bond_netlink_init(void); void bond_netlink_fini(void); -struct net_device *bond_option_active_slave_get_rcu(struct bonding *bond); +struct net_device *bond_option_active_slave_get_rcu(const struct bonding *bond); const char *bond_slave_link_status(s8 link); struct bond_vlan_tag *bond_verify_device_path(struct net_device *start_dev, struct net_device *end_dev,
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2.54.0.1032.g2f8565e1d1-goog