net: bridge: mst: fix suspicious rcu usage in br_mst_set_state

I converted br_mst_set_state to RCU to avoid a vlan use-after-free
but forgot to change the vlan group dereference helper. Switch to vlan
group RCU deref helper to fix the suspicious rcu usage warning.

Fixes: 3a7c1661ae13 ("net: bridge: mst: fix vlan use-after-free")
Reported-by: syzbot+9bbe2de1bc9d470eb5fe@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=9bbe2de1bc9d470eb5fe
Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://lore.kernel.org/r/20240609103654.914987-3-razor@blackwall.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/bridge/br_mst.c b/net/bridge/br_mst.c
index 1de72816b0fb257395507d884b10c399a5ee1b8b..1820f09ff59cebb6034febcc5e38334c4470dec6 100644 (file)
--- a/net/bridge/br_mst.c
+++ b/net/bridge/br_mst.c
@@ -102,7 +102,7 @@ int br_mst_set_state(struct net_bridge_port *p, u16 msti, u8 state,
        int err = 0;
 
        rcu_read_lock();
-       vg = nbp_vlan_group(p);
+       vg = nbp_vlan_group_rcu(p);
        if (!vg)
                goto out;