[syzbot] [bridge?] [netfilter?] WARNING in br_nf_local_in (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f417b7ffcbef Add linux-next specific files for 20260109
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12f625fa580000
kernel config: https://syzkaller.appspot.com/x/.config?x=63a1fc1b4011ac76
dashboard link: https://syzkaller.appspot.com/bug?extid=9c5dd93a81a3f39325c2
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1f048080a918/disk-f417b7ff.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/dfd5ea190c96/vmlinux-f417b7ff.xz
kernel image: https://storage.googleapis.com/syzbot-assets/db24c176e0df/bzImage-f417b7ff.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9c5dd9...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: net/bridge/br_netfilter_hooks.c:602 at br_nf_local_in+0x40e/0x470 net/bridge/br_netfilter_hooks.c:602, CPU#1: ksoftirqd/1/23
Modules linked in:
CPU: 1 UID: 0 PID: 23 Comm: ksoftirqd/1 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:br_nf_local_in+0x40e/0x470 net/bridge/br_netfilter_hooks.c:602
Code: 38 69 eb f7 e9 4b fc ff ff 44 89 e1 80 e1 07 38 c1 0f 8c a8 fc ff ff 4c 89 e7 e8 1d 69 eb f7 e9 9b fc ff ff e8 d3 98 84 f7 90 <0f> 0b 90 48 89 df e8 b7 2b 00 00 e9 5b fd ff ff e8 bd 98 84 f7 90
RSP: 0000:ffffc900001d6f38 EFLAGS: 00010246
RAX: ffffffff8a3c21ed RBX: ffff8880792ba140 RCX: ffff88801d6ddac0
RDX: 0000000000000100 RSI: 0000000000000002 RDI: 0000000000000001
RBP: 0000000000000002 R08: ffff88807903e183 R09: 1ffff1100f207c30
R10: dffffc0000000000 R11: ffffed100f207c31 R12: 0000000000000000
R13: ffff8880792ba1a8 R14: 1ffff1100f257435 R15: ffff88807903e180
FS: 0000000000000000(0000) GS:ffff888125d07000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa503fb1000 CR3: 0000000078d26000 CR4: 00000000003526f0
Call Trace:
<TASK>
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
nf_hook include/linux/netfilter.h:273 [inline]
NF_HOOK+0x251/0x390 include/linux/netfilter.h:316
br_handle_frame_finish+0x15c6/0x1c90 net/bridge/br_input.c:235
br_nf_hook_thresh net/bridge/br_netfilter_hooks.c:-1 [inline]
br_nf_pre_routing_finish+0x1364/0x1af0 net/bridge/br_netfilter_hooks.c:425
NF_HOOK+0x61b/0x6b0 include/linux/netfilter.h:318
br_nf_pre_routing+0xeb7/0x1470 net/bridge/br_netfilter_hooks.c:534
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
br_handle_frame+0x96e/0x14f0 net/bridge/br_input.c:442
__netif_receive_skb_core+0x95f/0x2f90 net/core/dev.c:6026
__netif_receive_skb_one_core net/core/dev.c:6137 [inline]
__netif_receive_skb+0x72/0x380 net/core/dev.c:6252
process_backlog+0x54f/0x1340 net/core/dev.c:6604
__napi_poll+0xae/0x320 net/core/dev.c:7668
napi_poll net/core/dev.c:7731 [inline]
net_rx_action+0x64a/0xe00 net/core/dev.c:7883
handle_softirqs+0x22b/0x7c0 kernel/softirq.c:626
run_ksoftirqd+0x36/0x60 kernel/softirq.c:1067
smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
kthread+0x389/0x480 kernel/kthread.c:467
ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>


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