syzbot


WARNING in nf_conntrack_cleanup_net_list (2)

Status: upstream: reported on 2026/05/29 20:02
Subsystems: netfilter
Labels: prio:normal
[Documentation on labels]
Reported-by: syzbot+122256c3e2bf6ec9f928@syzkaller.appspotmail.com
First crash: 56d, last: 24d
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
5c37299a-ac88-4bd7-8bef-ce8ff9942e6d assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in nf_conntrack_cleanup_net_list (2) 2026/05/29 23:15 2026/05/29 23:15 2026/05/29 23:51 6b4a844333e83556da95d61d7f207e7ef5cd4bc6

			
		
Discussions (2)
Title Replies (including bot) Last reply
[syzbot] Monthly netfilter report (Jul 2026) 0 (1) 2026/07/01 12:32
[syzbot] [netfilter?] WARNING in nf_conntrack_cleanup_net_list (2) 0 (1) 2026/05/29 20:02
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in nf_conntrack_cleanup_net_list netfilter -1 765 88d 222d 29/29 fixed on 2026/05/06 16:40

Sample crash report:
------------[ cut here ]------------
conntrack cleanup blocked for 60s
WARNING: net/netfilter/nf_conntrack_core.c:2504 at nf_conntrack_cleanup_net_list+0x4f7/0x6e0 net/netfilter/nf_conntrack_core.c:2504, CPU#0: kworker/u8:2/19802
Modules linked in:
CPU: 0 UID: 0 PID: 19802 Comm: kworker/u8:2 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/10/2026
Workqueue: netns cleanup_net
RIP: 0010:nf_conntrack_cleanup_net_list+0x4f7/0x6e0 net/netfilter/nf_conntrack_core.c:2504
Code: 29 c3 48 89 de e8 19 52 4a f8 48 85 db 78 0f e8 6f 57 4a f8 e8 3a e4 de 01 e9 0e fc ff ff e8 60 57 4a f8 48 8d 3d b9 a0 4b 07 <67> 48 0f b9 3a eb de 4c 8b 6c 24 40 e8 48 57 4a f8 48 b8 00 00 00
RSP: 0018:ffffc900077c7970 EFLAGS: 00010293
RAX: 0000000000000000 RBX: fffffffffffffffe RCX: ffffffff89bf28a7
RDX: ffff8880295eca80 RSI: ffffffff89bf28c0 RDI: ffffffff910ac980
RBP: 0000000000000001 R08: 0000000000000007 R09: 0000000000000000
R10: fffffffffffffffe R11: 0000000000000000 R12: 0000000000000001
R13: 0000000000000001 R14: ffffc900077c7b28 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8881240e0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555813dea48 CR3: 000000007ff26000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 ops_exit_list net/core/net_namespace.c:205 [inline]
 ops_undo_list+0x363/0xab0 net/core/net_namespace.c:252
 cleanup_net+0x499/0x920 net/core/net_namespace.c:702
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
----------------
Code disassembly (best guess):
   0:	29 c3                	sub    %eax,%ebx
   2:	48 89 de             	mov    %rbx,%rsi
   5:	e8 19 52 4a f8       	call   0xf84a5223
   a:	48 85 db             	test   %rbx,%rbx
   d:	78 0f                	js     0x1e
   f:	e8 6f 57 4a f8       	call   0xf84a5783
  14:	e8 3a e4 de 01       	call   0x1dee453
  19:	e9 0e fc ff ff       	jmp    0xfffffc2c
  1e:	e8 60 57 4a f8       	call   0xf84a5783
  23:	48 8d 3d b9 a0 4b 07 	lea    0x74ba0b9(%rip),%rdi        # 0x74ba0e3
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	eb de                	jmp    0xf
  31:	4c 8b 6c 24 40       	mov    0x40(%rsp),%r13
  36:	e8 48 57 4a f8       	call   0xf84a5783
  3b:	48                   	rex.W
  3c:	b8                   	.byte 0xb8
  3d:	00 00                	add    %al,(%rax)

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/28 01:50 upstream 780d569e6c4b fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in nf_conntrack_cleanup_net_list
2026/05/27 09:38 upstream d60ec36cab33 2b01f00e .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in nf_conntrack_cleanup_net_list
* Struck through repros no longer work on HEAD.