netdev - Re: [RFC PATCH v3 nf-next] selftests: netfilter: Add bridge

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Message-ID: <aNwtMiC22yOAO4Y6@strlen.de>
Date: Tue, 30 Sep 2025 21:19:14 +0200
From: Florian Westphal <fw@...len.de>
To: Eric Woudstra <ericwouds@...il.com>
Cc: Pablo Neira Ayuso <pablo@...filter.org>,
	Jozsef Kadlecsik <kadlec@...filter.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, Shuah Khan <shuah@...nel.org>,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	Vladimir Oltean <olteanv@...il.com>,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: Re: [RFC PATCH v3 nf-next] selftests: netfilter: Add
 bridge_fastpath.sh

Eric Woudstra <ericwouds@...il.com> wrote:
> Add a script to test various scenarios where a bridge is involved
> in the fastpath. It runs tests in the forward path, and also in
> a bridged path.

Why is this still an RFC, what is missing to appy this?

Also:

PASS:  forward,        without vlan-device, without vlan encap, client1, without fastpath

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]
 ...

I did not see a mention of this, nor a bug fix.

Its a pre-existing bug, br_vlan_fill_forward_path_pvid uses
br_vlan_group() instead of _rcu version.

Will you send a patch for this?