Subject: [PATCH v1 nf] bridge: br_vlan_fill_forward_path_pvid: use br_vlan_group_rcu()

From: Eric Woudstra <[email-masked]>
Date: Tue, 7 Oct 2025 10:15:01 +0200

Bug: br_vlan_fill_forward_path_pvid uses br_vlan_group() instead of
br_vlan_group_rcu(). Correct this bug.

Fixes: bcf2766b1377 ("net: bridge: resolve forwarding path for VLAN tag actions in bridge devices")
Signed-off-by: Eric Woudstra <[email-masked]>

---

Also see the debugging info send by Florian in mailing:
"[RFC PATCH v3 nf-next] selftests: netfilter: Add bridge_fastpath.sh"

net/bridge/br_private.h:1627 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
7 locks held by socat/410:
 #0: ffff88800d7a9c90 (sk_lock-AF_INET){+.+.}-{0:0}, at: inet_stream_connect+0x43/0xa0
 #1: ffffffff9a779900 (rcu_read_lock){....}-{1:3}, at: __ip_queue_xmit+0x62/0x1830
 #2: ffffffff9a779900 (rcu_read_lock){....}-{1:3}, at: ip_output+0x57/0x3c0
 #3: ffffffff9a779900 (rcu_read_lock){....}-{1:3}, at: ip_finish_output2+0x263/0x17d0
 #4: ffffffff9a779900 (rcu_read_lock){....}-{1:3}, at: process_backlog+0x38a/0x14b0
 #5: ffffffff9a779900 (rcu_read_lock){....}-{1:3}, at: netif_receive_skb_internal+0x83/0x330
 #6: ffffffff9a779900 (rcu_read_lock){....}-{1:3}, at: nf_hook.constprop.0+0x8a/0x440

stack backtrace:
CPU: 0 UID: 0 PID: 410 Comm: socat Not tainted 6.17.0-rc7-virtme #1 PREEMPT(full)
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Call Trace:
 <IRQ>
 dump_stack_lvl+0x6f/0xb0
 lockdep_rcu_suspicious.cold+0x4f/0xb1
 br_vlan_fill_forward_path_pvid+0x32c/0x410 [bridge]
 br_fill_forward_path+0x7a/0x4d0 [bridge]
 ...

 net/bridge/br_vlan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 939a3aa78d5c..54993a05037c 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -1455,7 +1455,7 @@ void br_vlan_fill_forward_path_pvid(struct net_bridge *br,
 	if (!br_opt_get(br, BROPT_VLAN_ENABLED))
 		return;
 
-	vg = br_vlan_group(br);
+	vg = br_vlan_group_rcu(br);
 
 	if (idx >= 0 &&
 	    ctx->vlan[idx].proto == br->vlan_proto) {
-- 
2.50.0