INFO: task kworker/u4:1:17607 blocked for more than 140 seconds.
      Not tainted 4.19.211-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:1    D27416 17607      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:2713
 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:554
 process_one_work+0x864/0x1570 kernel/workqueue.c:2153
 worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
 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:
netlink: 'syz-executor.4': attribute type 1 has an invalid length.
1 lock held by khungtaskd/1569:
 #0: 00000000321e73dc (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4441
1 lock held by in:imklog/7882:
 #0: 0000000003ae1dc2 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x26f/0x310 fs/file.c:767
2 locks held by agetty/8056:
 #0: 000000000ae5ea4a (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:272
 #1: 000000008dea1786 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x217/0x1950 drivers/tty/n_tty.c:2154
4 locks held by kworker/1:3/9357:
 #0: 00000000281dc858 ((wq_completion)"events"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2124
 #1: 000000003e04ffe7 ((work_completion)(&m->rq)){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2128
 #2: 000000000ae5ea4a (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:272
 #3: 000000008dea1786 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x217/0x1950 drivers/tty/n_tty.c:2154
3 locks held by kworker/0:36/13659:
 #0: 00000000281dc858 ((wq_completion)"events"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2124
 #1: 0000000096b3ca18 ((linkwatch_work).work){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2128
 #2: 0000000069aa34f8 (rtnl_mutex){+.+.}, at: linkwatch_event+0xb/0x60 net/core/link_watch.c:236
3 locks held by kworker/1:1/31348:
 #0: 00000000281dc858 ((wq_completion)"events"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2124
 #1: 000000001c93be75 ((work_completion)(&ns->proc_work)){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2128
 #2: 00000000783cf298 (rcu_preempt_state.exp_mutex){+.+.}, at: exp_funnel_lock kernel/rcu/tree_exp.h:297 [inline]
 #2: 00000000783cf298 (rcu_preempt_state.exp_mutex){+.+.}, at: _synchronize_rcu_expedited+0x4dc/0x6f0 kernel/rcu/tree_exp.h:667
4 locks held by kworker/1:2/3242:
 #0: 00000000281dc858 ((wq_completion)"events"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2124
 #1: 000000009a5079d8 ((work_completion)(&m->rq)){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2128
 #2: 000000000ae5ea4a (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:272
 #3: 000000008dea1786 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x217/0x1950 drivers/tty/n_tty.c:2154
3 locks held by kworker/u4:1/17607:
 #0: 00000000ca357ad6 ((wq_completion)"%s""netns"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2124
 #1: 000000000680db3e (net_cleanup_work){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2128
 #2: 00000000d32262b3 (pernet_ops_rwsem){++++}, at: cleanup_net+0xa8/0x8b0 net/core/net_namespace.c:521
2 locks held by kworker/1:4/19950:
 #0: 00000000281dc858 ((wq_completion)"events"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2124
 #1: 0000000082618686 ((work_completion)(&ns->proc_work)){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2128
1 lock held by syz-executor.2/30199:
 #0: 00000000b9a488d1 (rcu_preempt_state.barrier_mutex){+.+.}, at: _rcu_barrier+0x59/0x3e0 kernel/rcu/tree.c:3430
2 locks held by syz-executor.5/30182:
 #0: 000000009a91adae (&sb->s_type->i_mutex_key#13){+.+.}, at: inode_lock include/linux/fs.h:748 [inline]
 #0: 000000009a91adae (&sb->s_type->i_mutex_key#13){+.+.}, at: __sock_release+0x86/0x2a0 net/socket.c:598
 #1: 0000000069aa34f8 (rtnl_mutex){+.+.}, at: ip6mr_sk_done+0xe0/0x370 net/ipv6/ip6mr.c:1564
2 locks held by syz-executor.4/30192:
 #0: 00000000d36170df (&sb->s_type->i_mutex_key#13){+.+.}, at: inode_lock include/linux/fs.h:748 [inline]
 #0: 00000000d36170df (&sb->s_type->i_mutex_key#13){+.+.}, at: __sock_release+0x86/0x2a0 net/socket.c:598
 #1: 0000000069aa34f8 (rtnl_mutex){+.+.}, at: ip6mr_sk_done+0xe0/0x370 net/ipv6/ip6mr.c:1564
2 locks held by syz-executor.1/30240:
 #0: 0000000069aa34f8 (rtnl_mutex){+.+.}, at: rtnl_lock net/core/rtnetlink.c:77 [inline]
 #0: 0000000069aa34f8 (rtnl_mutex){+.+.}, at: rtnetlink_rcv_msg+0x3fe/0xb80 net/core/rtnetlink.c:4779
 #1: 00000000783cf298 (rcu_preempt_state.exp_mutex){+.+.}, at: exp_funnel_lock kernel/rcu/tree_exp.h:329 [inline]
 #1: 00000000783cf298 (rcu_preempt_state.exp_mutex){+.+.}, at: _synchronize_rcu_expedited+0x256/0x6f0 kernel/rcu/tree_exp.h:667

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 1569 Comm: khungtaskd Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1a6/0x1f0 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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 30240 Comm: syz-executor.1 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
RIP: 0010:validate_chain kernel/locking/lockdep.c:2427 [inline]
RIP: 0010:__lock_acquire+0x8ee/0x3ff0 kernel/locking/lockdep.c:3416
Code: 24 38 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e 96 26 00 00 41 8b 42 20 25 00 80 04 00 3d 00 00 04 00 0f 84 89 02 00 00 <48> c7 c2 60 f1 45 8a 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 0f
RSP: 0018:ffff88801635f308 EFLAGS: 00000046
RAX: 1ffffffff18f5f33 RBX: ffffffff8c7af980 RCX: 00000000000067e1
RDX: 1ffffffff19a9689 RSI: 00000000f6de57e7 RDI: ffffffff8c7af998
RBP: dffffc0000000000 R08: ffffffff8cd4b448 R09: 0000000000000001
R10: ffff888098fbac70 R11: 0000000000000000 R12: 3caf20bda2337fe9
R13: ffff888098fba3c0 R14: ffff888098fbac88 R15: 0000000000000000
FS:  00007fd5711ca700(0000) GS:ffff8880ba000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8f7cc12000 CR3: 0000000023226000 CR4: 00000000003406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000602
Call Trace:
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
 _raw_spin_lock_irq+0x5b/0x80 kernel/locking/spinlock.c:160
 spin_lock_irq include/linux/spinlock.h:354 [inline]
 __wait_for_common kernel/sched/completion.c:103 [inline]
 wait_for_common+0x9e/0x470 kernel/sched/completion.c:115
 _rcu_barrier+0x279/0x3e0 kernel/rcu/tree.c:3495
 netdev_run_todo+0x100/0xab0 net/core/dev.c:8972
 rtnl_unlock net/core/rtnetlink.c:117 [inline]
 rtnetlink_rcv_msg+0x460/0xb80 net/core/rtnetlink.c:4783
 netlink_rcv_skb+0x160/0x440 net/netlink/af_netlink.c:2463
 netlink_unicast_kernel net/netlink/af_netlink.c:1325 [inline]
 netlink_unicast+0x4d5/0x690 net/netlink/af_netlink.c:1351
 netlink_sendmsg+0x6c3/0xc50 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xc3/0x120 net/socket.c:661
 ___sys_sendmsg+0x7bb/0x8e0 net/socket.c:2227
 __sys_sendmsg net/socket.c:2265 [inline]
 __do_sys_sendmsg net/socket.c:2274 [inline]
 __se_sys_sendmsg net/socket.c:2272 [inline]
 __x64_sys_sendmsg+0x132/0x220 net/socket.c:2272
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7fd572c580a9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd5711ca168 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fd572d77f80 RCX: 00007fd572c580a9
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000004
RBP: 00007fd572cb3ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffcc67ef39f R14: 00007fd5711ca300 R15: 0000000000022000