WARNING in br_nf_local

WARNING in br_nf_local_in

Status: upstream: reported on 2025/09/09 05:13
Subsystems: bridge netfilter
[Documentation on labels]
Reported-by: syzbot+aa8e2b2bfec0dd8e7e81@syzkaller.appspotmail.com
Fix commit: netfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm
Patched on: [ci-qemu-gce-upstream-auto ci-qemu2-arm32 ci-qemu2-arm64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-linux-next-kasan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci-upstream-rust-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce], missing on: [ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-upstream-gce-arm64 ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci2-upstream-usb]
First crash: 6d16h, last: 6d16h

▶ ▼ Discussions (1)

Title	Replies (including bot)	Last reply
[syzbot] [bridge?] [netfilter?] WARNING in br_nf_local_in	2 (3)	2025/09/09 11:17

▶ ▼ Similar bugs (2)

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-5.15	WARNING in br_nf_local_in	-1				1	405d	405d	0/3	auto-obsoleted due to no activity on 2024/11/09 23:29
linux-5.15	WARNING in br_nf_local_in (2) origin:lts-only	-1	C		error	8	59d	245d	0/3	upstream: reported C repro on 2025/01/08 23:19

Sample crash report:

------------[ cut here ]------------
WARNING: CPU: 3 PID: 8841 at net/bridge/br_netfilter_hooks.c:630 br_nf_local_in+0x714/0x7f0 net/bridge/br_netfilter_hooks.c:630
Modules linked in:
CPU: 3 UID: 0 PID: 8841 Comm: syz.0.801 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:br_nf_local_in+0x714/0x7f0 net/bridge/br_netfilter_hooks.c:630
Code: 12 f7 4b f7 90 0f 0b 90 e9 e1 fb ff ff e8 04 f7 4b f7 be 03 00 00 00 48 89 ef e8 87 e8 73 fa e9 39 fa ff ff e8 ed f6 4b f7 90 <0f> 0b 90 e9 dc fd ff ff 4c 89 f7 e8 2c 56 b2 f7 e9 48 f9 ff ff 4c
RSP: 0018:ffffc9000500efc0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8a6f9520
RDX: ffff8880255b4880 RSI: ffffffff8a6f9743 RDI: 0000000000000001
RBP: ffff88803a6b2900 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000008
R13: ffff88803a6b29c0 R14: 0000000000000000 R15: ffff88803608d874
FS:  00007faf552176c0(0000) GS:ffff8880d69b8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007faf55216f98 CR3: 000000001fa82000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xbe/0x200 net/netfilter/core.c:623
 nf_hook.constprop.0+0x3e7/0x6b0 include/linux/netfilter.h:273
 NF_HOOK include/linux/netfilter.h:316 [inline]
 br_pass_frame_up+0x307/0x490 net/bridge/br_input.c:70
 br_handle_frame_finish+0xf5a/0x1ca0 net/bridge/br_input.c:227
 br_nf_hook_thresh+0x307/0x410 net/bridge/br_netfilter_hooks.c:1170
 br_nf_pre_routing_finish+0x8a1/0x1810 net/bridge/br_netfilter_hooks.c:425
 NF_HOOK include/linux/netfilter.h:318 [inline]
 NF_HOOK include/linux/netfilter.h:312 [inline]
 br_nf_pre_routing+0xf7b/0x15b0 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:283 [inline]
 br_handle_frame+0xad5/0x14b0 net/bridge/br_input.c:434
 __netif_receive_skb_core.constprop.0+0xa22/0x48c0 net/core/dev.c:5878
 __netif_receive_skb_one_core+0xb0/0x1e0 net/core/dev.c:5989
 __netif_receive_skb+0x1d/0x160 net/core/dev.c:6104
 netif_receive_skb_internal net/core/dev.c:6190 [inline]
 netif_receive_skb+0x137/0x7b0 net/core/dev.c:6249
 tun_rx_batched.isra.0+0x3ee/0x740 drivers/net/tun.c:1509
 tun_get_user+0x28e4/0x3ce0 drivers/net/tun.c:1950
 tun_chr_write_iter+0xdc/0x210 drivers/net/tun.c:1996
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x7d3/0x11d0 fs/read_write.c:686
 ksys_write+0x12a/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7faf5438d69f
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:00007faf55217000 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007faf545c5fa0 RCX: 00007faf5438d69f
RDX: 000000000000002a RSI: 0000200000000000 RDI: 00000000000000c8
RBP: 00007faf54411e19 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000002a R11: 0000000000000293 R12: 0000000000000000
R13: 00007faf545c6038 R14: 00007faf545c5fa0 R15: 00007fffb9e76588
 </TASK>

Crashes (1):
Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Assets (help?)	Manager	Title
2025/09/05 05:11	upstream	08b06c30a445	d291dd2d	.config	console log	report			info	[disk image (non-bootable)] [vmlinux] [kernel image]	ci-qemu-upstream	WARNING in br_nf_local_in

* ~~Struck through~~ repros no longer work on HEAD.