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: 46d, last: 12h22m
Cause bisection: failed (error log, bisect log)
  
▶ ▼ ✨ 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 (2)
Created Duration User Patch Repo Result
2026/10/30 04:55 12h32m bisect net error job log
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/1:1/29
Modules linked in:
CPU: 1 UID: 0 PID: 29 Comm: kworker/1:1 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 f0 9c a0 f7 41 bf 30 75 00 00 eb 0f e8 e3 9c a0 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:ffffc90000a57930 EFLAGS: 00010293
RAX: ffffffff8a27c93d RBX: ffff88807d532900 RCX: ffff888020e9ddc0
RDX: 0000000000000000 RSI: ffffffff9130fac0 RDI: 000000000000002f
RBP: 00000000fffffa56 R08: ffff888020e9ddc0 R09: 0000000000000002
R10: 0000000000000011 R11: 0000000000000000 R12: dffffc0000000000
R13: 1ffff1100faa6538 R14: ffff88807d532948 R15: 000000000000002f
FS:  0000000000000000(0000) GS:ffff888123b6b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000012000 CR3: 0000000074a9a000 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:3495 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
 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 (25):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/29 20:31 net dda51b737216 b1d00f76 .config console 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 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
2026/10/27 21:33 net-next 734bef548a96 96923c60 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-net-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
2026/10/28 20:48 upstream 65ba8f34ec88 858db2ec .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-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
2026/10/31 10:55 net cb284914e749 2041d3f8 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/31 02:27 net d8a4f4c59da5 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/31 02:15 net d8a4f4c59da5 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/30 17:15 net 5838f10563d5 b498adee .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/29 19:07 net dda51b737216 b1d00f76 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/29 14:16 net fd1436a75ceb b1d00f76 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/28 06:19 net 5d7f3375cd57 96923c60 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in nf_flow_table_extend_ct_timeout
2026/10/26 06:07 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 14:10 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
2026/10/25 23:13 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 7a19f0cc94ad 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in nf_flow_table_extend_ct_timeout
* Struck through repros no longer work on HEAD.