[PATCH net-next 2/2] vlan: no longer rely on RTNL in vlan_fill_info()
From: Eric Dumazet <edumazet@google.com>
Date: 2026-09-16 13:25:39
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
vlan_fill_info() used rcu_dereference_rtnl() to walk the egress priority map, forcing "ip link show" dumps to hold RTNL. The egress priority map is already fully RCU compliant: entries are published with rcu_assign_pointer() and freed with kfree_rcu() from vlan_dev_set_egress_priority() and vlan_dev_free_egress_priority(). Wrap the QoS mapping serialization in rcu_read_lock() / rcu_read_unlock() and use rcu_dereference(). Now that all the involved fields are annotated, use READ_ONCE() for vlan->flags, vlan->nr_ingress_mappings, vlan->nr_egress_mappings and vlan->ingress_priority_map[]. Also add missing const qualifiers in vlan_get_size() and vlan_fill_info(). Signed-off-by: Eric Dumazet <edumazet@google.com> --- net/8021q/vlan_netlink.c | 48 +++++++++++++++++++++++++--------------- 1 file changed, 30 insertions(+), 18 deletions(-)
diff --git a/net/8021q/vlan_netlink.c b/net/8021q/vlan_netlink.c
index 71cb98950511fe30f9b117834ce8b9107889f0cb..8c0c33cff4539f22d7fdca2bec68dc484c55209f 100644
--- a/net/8021q/vlan_netlink.c
+++ b/net/8021q/vlan_netlink.c@@ -209,7 +209,7 @@ static inline size_t vlan_qos_map_size(unsigned int n) static size_t vlan_get_size(const struct net_device *dev) { - struct vlan_dev_priv *vlan = vlan_dev_priv(dev); + const struct vlan_dev_priv *vlan = vlan_dev_priv(dev); return nla_total_size(2) + /* IFLA_VLAN_PROTOCOL */ nla_total_size(2) + /* IFLA_VLAN_ID */
@@ -220,60 +220,72 @@ static size_t vlan_get_size(const struct net_device *dev) static int vlan_fill_info(struct sk_buff *skb, const struct net_device *dev) { - struct vlan_dev_priv *vlan = vlan_dev_priv(dev); - struct vlan_priority_tci_mapping *pm; - struct ifla_vlan_flags f; + const struct vlan_dev_priv *vlan = vlan_dev_priv(dev); + const struct vlan_priority_tci_mapping *pm; struct ifla_vlan_qos_mapping m; + struct ifla_vlan_flags f; struct nlattr *nest; unsigned int i; + u32 flags; if (nla_put_be16(skb, IFLA_VLAN_PROTOCOL, vlan->vlan_proto) || nla_put_u16(skb, IFLA_VLAN_ID, vlan->vlan_id)) goto nla_put_failure; - if (vlan->flags) { - f.flags = vlan->flags; + + flags = READ_ONCE(vlan->flags); + if (flags) { + f.flags = flags; f.mask = ~0; if (nla_put(skb, IFLA_VLAN_FLAGS, sizeof(f), &f)) goto nla_put_failure; } - if (vlan->nr_ingress_mappings) { + + rcu_read_lock(); + + if (READ_ONCE(vlan->nr_ingress_mappings)) { nest = nla_nest_start_noflag(skb, IFLA_VLAN_INGRESS_QOS); - if (nest == NULL) - goto nla_put_failure; + if (!nest) + goto nla_put_failure_unlock; for (i = 0; i < ARRAY_SIZE(vlan->ingress_priority_map); i++) { - if (!vlan->ingress_priority_map[i]) + u32 skb_prio = READ_ONCE(vlan->ingress_priority_map[i]); + + if (!skb_prio) continue; m.from = i; - m.to = vlan->ingress_priority_map[i]; + m.to = skb_prio; if (nla_put(skb, IFLA_VLAN_QOS_MAPPING, sizeof(m), &m)) - goto nla_put_failure; + goto nla_put_failure_unlock; } nla_nest_end(skb, nest); } - if (vlan->nr_egress_mappings) { + if (READ_ONCE(vlan->nr_egress_mappings)) { nest = nla_nest_start_noflag(skb, IFLA_VLAN_EGRESS_QOS); - if (nest == NULL) - goto nla_put_failure; + if (!nest) + goto nla_put_failure_unlock; for (i = 0; i < ARRAY_SIZE(vlan->egress_priority_map); i++) { - for (pm = rcu_dereference_rtnl(vlan->egress_priority_map[i]); pm; - pm = rcu_dereference_rtnl(pm->next)) { + for (pm = rcu_dereference(vlan->egress_priority_map[i]); pm; + pm = rcu_dereference(pm->next)) { u16 vlan_qos = READ_ONCE(pm->vlan_qos); + m.from = pm->priority; m.to = (vlan_qos >> 13) & 0x7; if (nla_put(skb, IFLA_VLAN_QOS_MAPPING, sizeof(m), &m)) - goto nla_put_failure; + goto nla_put_failure_unlock; } } nla_nest_end(skb, nest); } + rcu_read_unlock(); return 0; +nla_put_failure_unlock: + rcu_read_unlock(); nla_put_failure: return -EMSGSIZE; }
--
2.55.0.1032.g73a4cd73de-goog