WARNING in nf_flow_table_extend_ct_timeout

Status: upstream: reported C repro on 2026/09/15 22:34
Subsystems: netfilter
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+521f7e7e2b974abde99a@syzkaller.appspotmail.com
First crash: 39d, last: 47m
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
2e4b5b9f repro-c 💥 WARNING in nf_flow_table_extend_ct_timeout 2026/10/18 20:33 2026/10/18 20:33 2026/10/18 21:28 432c0077
b864c2e7 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ✅ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ WARNING in nf_flow_table_extend_ct_timeout 2026/09/17 03:04 2026/09/17 03:04 2026/09/17 03:39 95928915
▶ ▼ Discussions (3)
Title Replies (including bot) Last reply
[syzbot] [netfilter?] WARNING in nf_flow_table_extend_ct_timeout 1 (6) 2026/10/22 17:29
[PATCH nf] netfilter: flowtable: extend ct timeout of offloaded GRE flows 1 (1) 2026/10/20 10:35
[syzbot] Monthly netfilter report (Oct 2026) 0 (1) 2026/10/02 20:33
▶ ▼ Last patch testing requests (3)
Created Duration User Patch Repo Result
2026/10/22 17:29 5h35m mike.michalo@gmail.com patch https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net main OK job log log
2026/10/22 17:24 1m mike.michalo@gmail.com patch https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git main error job log
2026/10/22 17:02 1m mike.michalo@gmail.com patch git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git main error job log
▶ ▼ Cause bisection attempts (1)
Created Duration User Patch Repo Result
2026/10/22 17:25 0m bisect net error

Sample crash report:
------------[ 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>

Crashes (13):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/22 16:44 net abeacca61eea 4ba27f85 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/22 18:04 net-next 279d5c8afcd3 4ba27f85 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/09/26 07:15 upstream 6812ce4e4379 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in nf_flow_table_extend_ct_timeout
2026/09/16 19:59 upstream 50d05c7c76c9 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in nf_flow_table_extend_ct_timeout
2026/09/16 00:30 upstream 50d05c7c76c9 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in nf_flow_table_extend_ct_timeout
2026/09/15 16:44 upstream 50d05c7c76c9 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in nf_flow_table_extend_ct_timeout
2026/10/25 14:10 net 7076f684d513 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/25 14:08 net 7076f684d513 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/25 14:08 net 7076f684d513 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/25 14:06 net 7076f684d513 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/23 23:16 net 734bef548a96 d566bfda .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/23 00:29 net f4377bf85887 4ba27f85 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/22 14:30 net abeacca61eea 4ba27f85 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
* Struck through repros no longer work on HEAD.