INFO: task kworker/u4:4:3605 blocked for more than 140 seconds. Not tainted 4.19.166-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u4:4 D25432 3605 2 0x80000000 Workqueue: netns cleanup_net Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x887/0x2040 kernel/sched/core.c:3517 schedule+0x8d/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x92d/0xfe0 kernel/time/timer.c:1794 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common+0x29c/0x470 kernel/sched/completion.c:115 flush_workqueue+0x40b/0x13e0 kernel/workqueue.c:2715 flush_scheduled_work include/linux/workqueue.h:599 [inline] tipc_exit_net+0x38/0x60 net/tipc/core.c:100 ops_exit_list+0xa5/0x150 net/core/net_namespace.c:153 cleanup_net+0x3b4/0x8b0 net/core/net_namespace.c:553 process_one_work+0x864/0x1570 kernel/workqueue.c:2155 worker_thread+0x64c/0x1130 kernel/workqueue.c:2298 kthread+0x33f/0x460 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Showing all locks held in the system: 3 locks held by kworker/u4:0/7: #0: 000000009989ad72 (&rq->lock){-.-.}, at: idle_balance kernel/sched/fair.c:9701 [inline] #0: 000000009989ad72 (&rq->lock){-.-.}, at: pick_next_task_fair+0x556/0x1570 kernel/sched/fair.c:6840 #1: 0000000025f07736 (rcu_read_lock){....}, at: cpu_of kernel/sched/sched.h:921 [inline] #1: 0000000025f07736 (rcu_read_lock){....}, at: __update_idle_core+0x39/0x3e0 kernel/sched/fair.c:6057 #2: 00000000595dd3aa (&base->lock){-.-.}, at: lock_timer_base+0x55/0x1b0 kernel/time/timer.c:950 1 lock held by khungtaskd/1566: #0: 0000000025f07736 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4440 3 locks held by kworker/u4:4/3605: #0: 000000006e63a5c1 ((wq_completion)"%s""netns"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2126 #1: 000000007b1190c1 (net_cleanup_work){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2130 #2: 0000000025e8c27e (pernet_ops_rwsem){++++}, at: cleanup_net+0xa8/0x8b0 net/core/net_namespace.c:520 3 locks held by kworker/0:3/4715: #0: 000000008d0c13a9 ((wq_completion)"events"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2126 #1: 00000000c6e31e23 ((work_completion)(&smc->tcp_listen_work)){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2130 #2: 00000000e8155de4 (&smc->clcsock_release_lock){+.+.}, at: smc_clcsock_accept net/smc/af_smc.c:843 [inline] #2: 00000000e8155de4 (&smc->clcsock_release_lock){+.+.}, at: smc_tcp_listen_work+0x191/0xce0 net/smc/af_smc.c:1314 1 lock held by in:imklog/7813: #0: 00000000bed940d8 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x26f/0x310 fs/file.c:767 1 lock held by syz-executor.1/18196: #0: 000000008dafd3ba (sk_lock-AF_INET6){+.+.}, at: lock_sock include/net/sock.h:1510 [inline] #0: 000000008dafd3ba (sk_lock-AF_INET6){+.+.}, at: sctp_getsockopt+0x290/0x5dab net/sctp/socket.c:7428 1 lock held by syz-executor.3/21827: #0: 0000000025e8c27e (pernet_ops_rwsem){++++}, at: register_netdevice_notifier+0x7b/0x5b0 net/core/dev.c:1639 1 lock held by syz-executor.3/21833: #0: 0000000025e8c27e (pernet_ops_rwsem){++++}, at: register_netdevice_notifier+0x7b/0x5b0 net/core/dev.c:1639 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1566 Comm: khungtaskd Not tainted 4.19.166-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1fc/0x2fe lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x1a6/0x1eb lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline] watchdog+0x991/0xe60 kernel/hung_task.c:287 kthread+0x33f/0x460 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 4692 Comm: systemd-journal Not tainted 4.19.166-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__trace_hardirqs_on_caller kernel/locking/lockdep.c:2842 [inline] RIP: 0010:lockdep_hardirqs_on+0x338/0x5c0 kernel/locking/lockdep.c:2883 Code: 08 3c 03 0f 8e 65 01 00 00 8b 83 30 08 00 00 48 8d bb 48 08 00 00 48 89 fa 48 c1 ea 03 8d 68 01 48 b8 00 00 00 00 00 fc ff df <89> ab 30 08 00 00 0f b6 04 02 84 c0 74 08 3c 03 0f 8e 38 01 00 00 RSP: 0018:ffff8880a0eefe28 EFLAGS: 00000802 RAX: dffffc0000000000 RBX: ffff8880a0ee25c0 RCX: 0000000000000000 RDX: 1ffff110141dc5c1 RSI: 0000000000000001 RDI: ffff8880a0ee2e08 RBP: 0000000000140529 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff89f87f40 R13: ffff8880ba12be00 R14: ffff8880ba12be80 R15: ffff8880ba12be38 FS: 00007f996730f8c0(0000) GS:ffff8880ba100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f9964862000 CR3: 00000000a26a9000 CR4: 00000000001426e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __call_rcu.constprop.0+0x245/0x7f0 kernel/rcu/tree.c:3031 task_work_run+0x148/0x1c0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:193 [inline] exit_to_usermode_loop+0x251/0x2a0 arch/x86/entry/common.c:167 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f996689f840 Code: 73 01 c3 48 8b 0d 68 77 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 89 bb 20 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 1e f6 ff ff 48 89 04 24 RSP: 002b:00007ffd702f0df8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002 RAX: fffffffffffffffe RBX: 00007ffd702f1100 RCX: 00007f996689f840 RDX: 00000000000001a0 RSI: 0000000000080042 RDI: 000055f61a44d620 RBP: 000000000000000d R08: 000000000000ffc0 R09: 00000000ffffffff R10: 0000000000000069 R11: 0000000000000246 R12: 00000000ffffffff R13: 000055f61a441040 R14: 00007ffd702f10c0 R15: 000055f61a44cf50