[PATCH net v2 2/2] net: bridge: fix MST static key usage
From: Nikolay Aleksandrov <razor@blackwall.org>
Date: 2025-11-05 11:20:14
Also in:
bridge
Subsystem:
ethernet bridge, networking [general], the rest · Maintainers:
Nikolay Aleksandrov, Ido Schimmel, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
As Ido pointed out, the static key usage in MST is buggy and should use
inc/dec instead of enable/disable because we can have multiple bridges
with MST enabled which means a single bridge can disable MST for all.
Use static_branch_inc/dec to avoid that. When destroying a bridge decrement
the key if MST was enabled.
Fixes: ec7328b59176 ("net: bridge: mst: Multiple Spanning Tree (MST) mode")
Reported-by: Ido Schimmel <idosch@nvidia.com>
Closes: https://lore.kernel.org/netdev/20251104120313.1306566-1-razor@blackwall.org/T/#m6888d87658f94ed1725433940f4f4ebb00b5a68b (local)
Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>
---
v2: new fix
net/bridge/br_if.c | 1 +
net/bridge/br_mst.c | 10 ++++++++--
net/bridge/br_private.h | 5 +++++
3 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index 98c5b9c3145f..ca3a637d7cca 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c@@ -386,6 +386,7 @@ void br_dev_delete(struct net_device *dev, struct list_head *head) del_nbp(p); } + br_mst_uninit(br); br_recalculate_neigh_suppress_enabled(br); br_fdb_delete_by_port(br, NULL, 0, 1);
diff --git a/net/bridge/br_mst.c b/net/bridge/br_mst.c
index 3f24b4ee49c2..43a300ae6bfa 100644
--- a/net/bridge/br_mst.c
+++ b/net/bridge/br_mst.c@@ -22,6 +22,12 @@ bool br_mst_enabled(const struct net_device *dev) } EXPORT_SYMBOL_GPL(br_mst_enabled); +void br_mst_uninit(struct net_bridge *br) +{ + if (br_opt_get(br, BROPT_MST_ENABLED)) + static_branch_dec(&br_mst_used); +} + int br_mst_get_info(const struct net_device *dev, u16 msti, unsigned long *vids) { const struct net_bridge_vlan_group *vg;
@@ -225,9 +231,9 @@ int br_mst_set_enabled(struct net_bridge *br, bool on, return err; if (on) - static_branch_enable(&br_mst_used); + static_branch_inc(&br_mst_used); else - static_branch_disable(&br_mst_used); + static_branch_dec(&br_mst_used); br_opt_toggle(br, BROPT_MST_ENABLED, on); return 0;
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index b571d6f61389..7280c4e9305f 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h@@ -1954,6 +1954,7 @@ int br_mst_fill_info(struct sk_buff *skb, const struct net_bridge_vlan_group *vg); int br_mst_process(struct net_bridge_port *p, const struct nlattr *mst_attr, struct netlink_ext_ack *extack); +void br_mst_uninit(struct net_bridge *br); #else static inline bool br_mst_is_enabled(const struct net_bridge_port *p) {
@@ -1989,6 +1990,10 @@ static inline int br_mst_process(struct net_bridge_port *p, { return -EOPNOTSUPP; } + +static inline void br_mst_uninit(struct net_bridge *br) +{ +} #endif struct nf_br_ops {
--
2.51.0