syzbot


WARNING in nf_ct_bridge_post

Status: upstream: reported C repro on 2025/11/19 13:14
Subsystems: bridge netfilter
[Documentation on labels]
Reported-by: syzbot+a8ba738fe2db6b4bb27f@syzkaller.appspotmail.com
First crash: 6d09h, last: 6d04h
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [bridge?] [netfilter?] WARNING in nf_ct_bridge_post 0 (1) 2025/11/19 13:14

Sample crash report:
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>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/19 03:57 upstream 5bebe8de1926 ef766cd7 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in nf_ct_bridge_post
2025/11/19 02:07 upstream 5bebe8de1926 ef766cd7 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in nf_ct_bridge_post
2025/11/19 00:25 upstream 5bebe8de1926 ef766cd7 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in nf_ct_bridge_post
2025/11/18 22:43 upstream 5bebe8de1926 ef766cd7 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in nf_ct_bridge_post
* Struck through repros no longer work on HEAD.