linux-kernel - [syzbot] [bridge?] [netfilter?] WARNING in nf_ct_bridge

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Message-ID: <691dc2ac.050a0220.2ffa18.0005.GAE@google.com>
Date: Wed, 19 Nov 2025 05:14:20 -0800
From: syzbot <syzbot+a8ba738fe2db6b4bb27f@...kaller.appspotmail.com>
To: bridge@...ts.linux.dev, coreteam@...filter.org, davem@...emloft.net, 
	edumazet@...gle.com, fw@...len.de, horms@...nel.org, idosch@...dia.com, 
	kadlec@...filter.org, kuba@...nel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org, pabeni@...hat.com, 
	pablo@...filter.org, phil@....cc, razor@...ckwall.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [bridge?] [netfilter?] WARNING in nf_ct_bridge_post

Hello,

syzbot found the following issue on:

HEAD commit:    5bebe8de1926 mm/huge_memory: Fix initialization of huge ze..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1526e97c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a1db0fea040c2a9f
dashboard link: https://syzkaller.appspot.com/bug?extid=a8ba738fe2db6b4bb27f
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13fca8b4580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=121b7332580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-5bebe8de.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/45a180eaa13d/vmlinux-5bebe8de.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9ba2dcafae20/bzImage-5bebe8de.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a8ba738fe2db6b4bb27f@...kaller.appspotmail.com

bridge0: received packet on syz_tun with own address as source address (addr:aa:aa:aa:aa:aa:aa, vlan:1)
------------[ cut here ]------------
WARNING: CPU: 0 PID: 5876 at net/bridge/netfilter/nf_conntrack_bridge.c:357 nf_ct_bridge_refrag net/bridge/netfilter/nf_conntrack_bridge.c:357 [inline]
WARNING: CPU: 0 PID: 5876 at net/bridge/netfilter/nf_conntrack_bridge.c:357 nf_ct_bridge_post+0x3ff/0x1060 net/bridge/netfilter/nf_conntrack_bridge.c:408
Modules linked in:
CPU: 0 UID: 0 PID: 5876 Comm: syz.3.94 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:nf_ct_bridge_refrag net/bridge/netfilter/nf_conntrack_bridge.c:357 [inline]
RIP: 0010:nf_ct_bridge_post+0x3ff/0x1060 net/bridge/netfilter/nf_conntrack_bridge.c:408
Code: 89 ff 48 89 da 48 8d 8c 24 40 01 00 00 49 c7 c0 40 0c 2a 8a e8 12 d6 e1 ff 41 bf 02 00 00 00 e9 9c 07 00 00 e8 d2 1a 96 f7 90 <0f> 0b 90 45 31 ff e9 8b 07 00 00 e8 c1 1a 96 f7 eb 05 e8 ba 1a 96
RSP: 0018:ffffc9000d996ae0 EFLAGS: 00010293
RAX: ffffffff8a29f88e RBX: ffff888050bc0140 RCX: ffff88803b2b0000
RDX: 0000000000000000 RSI: ffffffff8f40f220 RDI: 0000000000000081
RBP: ffffc9000d996cc0 R08: ffff88803b2b0000 R09: 0000000000000002
R10: 000000000000dd86 R11: 0000000000000000 R12: 1ffff1100a17802e
R13: dffffc0000000000 R14: ffffc9000d996d80 R15: 0000000000000081
FS:  00007f027c05e6c0(0000) GS:ffff88808d730000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000000c0 CR3: 0000000059f5b000 CR4: 0000000000352ef0
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+0x215/0x3c0 include/linux/netfilter.h:316
 br_forward_finish+0xd3/0x130 net/bridge/br_forward.c:66
 NF_HOOK+0x320/0x3c0 include/linux/netfilter.h:318
 __br_forward+0x41e/0x600 net/bridge/br_forward.c:115
 deliver_clone net/bridge/br_forward.c:131 [inline]
 maybe_deliver+0xb5/0x160 net/bridge/br_forward.c:191
 br_flood+0x31a/0x6a0 net/bridge/br_forward.c:238
 br_handle_frame_finish+0x15a3/0x1c90 net/bridge/br_input.c:229
 nf_hook_bridge_pre net/bridge/br_input.c:313 [inline]
 br_handle_frame+0xb75/0x14f0 net/bridge/br_input.c:442
 __netif_receive_skb_core+0x10b9/0x4380 net/core/dev.c:5966
 __netif_receive_skb_one_core net/core/dev.c:6077 [inline]
 __netif_receive_skb+0x72/0x380 net/core/dev.c:6192
 netif_receive_skb_internal net/core/dev.c:6278 [inline]
 netif_receive_skb+0x1cb/0x790 net/core/dev.c:6337
 tun_rx_batched+0x1b9/0x730 drivers/net/tun.c:1485
 tun_get_user+0x2b65/0x3e90 drivers/net/tun.c:1953
 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1999
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5c9/0xb30 fs/read_write.c:686
 ksys_write+0x145/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f027b18e17f
Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 f9 92 02 00 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 4c 93 02 00 48
RSP: 002b:00007f027c05e000 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f027b3e6090 RCX: 00007f027b18e17f
RDX: 000000000000004e RSI: 0000200000000500 RDI: 00000000000000c8
RBP: 00007f027b211f91 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000004e R11: 0000000000000293 R12: 0000000000000000
R13: 00007f027b3e6128 R14: 00007f027b3e6090 R15: 00007ffc84bca4a8
 </TASK>


---
This report is generated by a bot. It may contain errors.
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If the report is already addressed, let syzbot know by replying with:
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