Re: [syzbot] [netfilter?] WARNING in nf_flow_table_extend_ct_timeout

[mixalhs]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git main

On Thu, Oct 22, 2026 at 6:44 PM syzbot
<syzbot+521f7e7e2b974abde99a@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    abeacca61eea Merge branch 'net-mlx5-hws-fix-modify-header-..
> git tree:       net
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=111f4d0d580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c4b098695335c89f
> dashboard link: https://syzkaller.appspot.com/bug?extid=521f7e7e2b974abde99a
> compiler:       Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1491e029580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=157d410d580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/22930d0e9391/disk-abeacca6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/d2e18d51f288/vmlinux-abeacca6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/69879bb16225/bzImage-abeacca6.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+521f7e7e2b974abde99a@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ------------[ cut here ]------------
> 1
> WARNING: net/netfilter/nf_flow_table_core.c:553 at nf_flow_table_extend_ct_timeout+0x1ee/0x2f0 net/netfilter/nf_flow_table_core.c:553, CPU#1: kworker/1:2/123
> Modules linked in:
> CPU: 1 UID: 0 PID: 123 Comm: kworker/1:2 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
> Workqueue: events_power_efficient nf_flow_offload_work_gc
> RIP: 0010:nf_flow_table_extend_ct_timeout+0x1ee/0x2f0 net/netfilter/nf_flow_table_core.c:553
> Code: 00 00 00 41 83 ff 06 0f 84 9a 00 00 00 41 83 ff 05 0f 85 b0 00 00 00 e8 e0 10 a9 f7 41 bf 30 75 00 00 eb 0f e8 d3 10 a9 f7 90 <0f> 0b 90 41 bf 01 00 00 00 48 c7 c0 80 f2 a0 8f 48 c1 e8 03 42 80
> RSP: 0018:ffffc90002dcf930 EFLAGS: 00010293
> RAX: ffffffff8a1effad RBX: ffff888027a52900 RCX: ffff88801ffa1f40
> RDX: 0000000000000000 RSI: ffffffff912fa640 RDI: 000000000000002f
> RBP: 0000000000000737 R08: ffff88801ffa1f40 R09: 0000000000000002
> R10: 0000000000000011 R11: 0000000000000000 R12: dffffc0000000000
> R13: 1ffff11004f4a538 R14: ffff888027a52948 R15: 000000000000002f
> FS:  0000000000000000(0000) GS:ffff888123bbd000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f926bd5bd3c CR3: 000000000fb48000 CR4: 00000000003526f0
> Call Trace:
>  <TASK>
>  nf_flow_offload_gc_step+0x5aa/0x840 net/netfilter/nf_flow_table_core.c:593
>  nf_flow_table_iterate+0x13c/0x1f0 net/netfilter/nf_flow_table_core.c:459
>  nf_flow_table_gc_run net/netfilter/nf_flow_table_core.c:616 [inline]
>  nf_flow_offload_work_gc+0x22/0x70 net/netfilter/nf_flow_table_core.c:624
>  process_one_work kernel/workqueue.c:3396 [inline]
>  process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
>  worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
>  kthread+0x38b/0x480 kernel/kthread.c:436
>  ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>  </TASK>
>
>
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.

Attachment: 0001-netfilter-flowtable-extend-ct-timeout-of-offloaded-G.patch
Description: Binary data