INFO: task hung in register_nexthop_notifier (8)

Status: closed as invalid on 2026/10/06 01:52
Subsystems: net
Labels: prio:normal
[Documentation on labels]
First crash: 284d, last: 27d
Cause bisection: failed (error log, bisect log)
  
Fix bisection: failed (error log, bisect log)
  
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
7595694e assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: task hung in register_nexthop_notifier (8) 2026/05/30 15:02 2026/05/30 15:02 2026/05/30 16:10 6b4a8443
5f3907b2 assessment-security 💥 INFO: task hung in register_nexthop_notifier (8) 2026/05/14 10:43 2026/05/14 10:43 2026/05/14 10:44 6ccb967e
▶ ▼ Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: task hung in register_nexthop_notifier 1 4 865d 889d 0/3 auto-obsoleted due to no activity on 2024/09/21 15:59
upstream INFO: task hung in register_nexthop_notifier (6) net 1 1 511d 511d 0/29 auto-obsoleted due to no activity on 2025/08/31 07:52
upstream INFO: task hung in register_nexthop_notifier net 1 1 2130d 2130d 0/29 auto-closed as invalid on 2021/03/26 11:18
upstream INFO: task hung in register_nexthop_notifier (2) net 1 1 1834d 1834d 0/29 auto-closed as invalid on 2022/01/16 12:31
upstream INFO: task hung in register_nexthop_notifier (5) netfilter 1 5 608d 704d 0/29 auto-obsoleted due to no activity on 2025/05/26 10:08
upstream INFO: task hung in register_nexthop_notifier (7) net 1 1 394d 394d 0/29 auto-obsoleted due to no activity on 2025/12/26 02:26
upstream INFO: task hung in register_nexthop_notifier (3) net 1 44 842d 952d 26/29 fixed on 2024/07/09 19:14
linux-6.1 INFO: task hung in register_nexthop_notifier 1 3 862d 888d 0/3 auto-obsoleted due to no activity on 2024/09/25 01:20
linux-6.6 INFO: task hung in register_nexthop_notifier 1 1 326d 326d 0/2 auto-obsoleted due to no activity on 2026/03/14 08:44
▶ ▼ Last patch testing requests (3)
Created Duration User Patch Repo Result
2026/07/20 00:09 1h01m retest repro upstream log
2026/05/09 23:50 36m retest repro upstream report log
2026/02/12 13:41 22m retest repro upstream report log

Sample crash report:
INFO: task syz-executor:6164 blocked for more than 159 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:25144 pid:6164  tgid:6164  ppid:1      task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5260 [inline]
 __schedule+0x14ea/0x5050 kernel/sched/core.c:6867
 __schedule_loop kernel/sched/core.c:6949 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:6964
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7021
 __mutex_lock_common kernel/locking/mutex.c:692 [inline]
 __mutex_lock+0x7fe/0x1300 kernel/locking/mutex.c:776
 register_nexthop_notifier+0x88/0x290 net/ipv4/nexthop.c:3971
 ops_init+0x35c/0x5c0 net/core/net_namespace.c:137
 setup_net+0x118/0x340 net/core/net_namespace.c:446
 copy_net_ns+0x50e/0x730 net/core/net_namespace.c:581
 create_new_namespaces+0x3e7/0x6a0 kernel/nsproxy.c:130
 unshare_nsproxy_namespaces+0x11a/0x160 kernel/nsproxy.c:226
 ksys_unshare+0x4f4/0x900 kernel/fork.c:3171
 __do_sys_unshare kernel/fork.c:3242 [inline]
 __se_sys_unshare kernel/fork.c:3240 [inline]
 __x64_sys_unshare+0x38/0x50 kernel/fork.c:3240
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f982259c1a7
RSP: 002b:00007fff89580da8 EFLAGS: 00000206 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f982259c1a7
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 00007fff89580e00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 00007fff89580e08
R13: 0000000000000002 R14: 00007fff89580fe8 R15: 0000000000000000
 </TASK>

Showing all locks held in the system:
1 lock held by pool_workqueue_/3:
 #0: ffffffff8e560c78 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:343 [inline]
 #0: ffffffff8e560c78 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x38d/0x770 kernel/rcu/tree_exp.h:956
1 lock held by kworker/R-rcu_g/4:

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/29 11:06 upstream 8dfce8991b95 b78a7341 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in register_nexthop_notifier
2026/09/20 06:38 upstream 518e5b794c06 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in register_nexthop_notifier
2026/09/13 10:34 upstream cba2348ab114 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: task hung in register_nexthop_notifier
2026/08/07 17:38 upstream f9a2394a2348 e4ef95d6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in register_nexthop_notifier
2026/03/13 22:16 upstream 0257f64bdac7 351cb5cf .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in register_nexthop_notifier
2026/09/24 04:34 upstream fe2ec83746e5 0a1606bc .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: task hung in register_nexthop_notifier
2026/09/04 12:35 net adf50c47a47f 801f0966 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: task hung in register_nexthop_notifier
2026/01/16 00:34 net 851822aec1a3 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: task hung in register_nexthop_notifier
2026/03/25 19:37 net-next d1e59a469737 4367a094 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: task hung in register_nexthop_notifier
2026/09/29 18:22 linux-next 6375e61c01e9 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: task hung in register_nexthop_notifier
2026/08/25 11:18 linux-next 4b18edbd8e70 614e416a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: task hung in register_nexthop_notifier
* Struck through repros no longer work on HEAD.