INFO: task syz.3.784:8115 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.784       state:D stack:26920 pid:8115  tgid:8115  ppid:7731   task_flags:0x400040 flags:0x00004006
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7e6/0x1350
 nfsd_shutdown_threads+0x4e/0xd0
 nfsd_umount+0x42/0xd0
 deactivate_locked_super+0xbc/0x130
 cleanup_mnt+0x425/0x4c0
 task_work_run+0x1d4/0x260
 exit_to_user_mode_loop+0xec/0x110
 do_syscall_64+0x2bd/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc48e38eba9
RSP: 002b:00007ffc2ea08da8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 0000000000028e29 RCX: 00007fc48e38eba9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fc48e5d7da0 R08: 0000000000000001 R09: 000000052ea0909f
R10: 0000001b2e920000 R11: 0000000000000246 R12: 00007fc48e5d5fac
R13: 00007fc48e5d5fa0 R14: ffffffffffffffff R15: 00007ffc2ea08ec0
 </TASK>
INFO: task syz.2.795:8156 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.795       state:D stack:25896 pid:8156  tgid:8155  ppid:5847   task_flags:0x400140 flags:0x00004004
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 schedule_preempt_disabled+0x13/0x30
 rwsem_down_read_slowpath+0x5fd/0x8f0
 down_read+0x98/0x2e0
 super_lock+0x2a9/0x3b0
 __iterate_supers+0x126/0x290
 ksys_sync+0x94/0x150
 __ia32_sys_sync+0xe/0x20
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f680878eba9
RSP: 002b:00007f6809649038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007f68089d5fa0 RCX: 00007f680878eba9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f68089d5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f68089d6038 R14: 00007f68089d5fa0 R15: 00007ffebe167cc8
 </TASK>
INFO: task syz.2.795:8170 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.795       state:D stack:28936 pid:8170  tgid:8155  ppid:5847   task_flags:0x400040 flags:0x00004004
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 schedule_preempt_disabled+0x13/0x30
 rwsem_down_read_slowpath+0x5fd/0x8f0
 down_read+0x98/0x2e0
 super_lock+0x2a9/0x3b0
 __iterate_supers+0x126/0x290
 ksys_sync+0x94/0x150
 __ia32_sys_sync+0xe/0x20
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f680878eba9
RSP: 002b:00007f6809628038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007f68089d6090 RCX: 00007f680878eba9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f68089d6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f68089d6128 R14: 00007f68089d6090 R15: 00007ffebe167cc8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/34:
 #0: ffffffff8e139f20 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
3 locks held by udevd/5297:
1 lock held by udevd/5850:
1 lock held by udevd/5859:
1 lock held by udevd/5860:
1 lock held by udevd/5997:
2 locks held by getty/6067:
 #0: ffff8880255d90a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900027282f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400
1 lock held by udevd/7633:
1 lock held by udevd/7763:
2 locks held by syz.0.697/7860:
 #0: ffffffff8f59f130 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40
 #1: ffffffff8e418648 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_threads_set_doit+0x2cb/0x960
2 locks held by syz.3.784/8115:
 #0: ffff8880296960e0 (&type->s_umount_key#120){++++}-{4:4}, at: deactivate_super+0xa9/0xe0
 #1: ffffffff8e418648 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x4e/0xd0
1 lock held by syz.2.795/8156:
 #0: ffff8880296960e0 (&type->s_umount_key#120){++++}-{4:4}, at: super_lock+0x2a9/0x3b0
1 lock held by syz.2.795/8170:
 #0: ffff8880296960e0 (&type->s_umount_key#120){++++}-{4:4}, at: super_lock+0x2a9/0x3b0
3 locks held by kworker/u9:11/8736:
 #0: ffff88801a489148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc90004f37bc0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffffffff8f539b08 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60
1 lock held by syz.7.1058/9193:
2 locks held by syz.6.1072/9249:
 #0: ffffffff8f539b08 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x3e/0x1c0
 #1: ffffffff8e13f9b8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x2f6/0x730

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 34 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 nmi_cpu_backtrace+0x39e/0x3d0
 nmi_trigger_cpumask_backtrace+0x17a/0x300
 watchdog+0xf93/0xfe0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 9249 Comm: syz.6.1072 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:rcu_is_watching+0x31/0xb0
Code: 56 53 65 ff 05 30 50 fa 10 e8 1b e1 d3 09 89 c3 83 f8 08 73 65 49 bf 00 00 00 00 00 fc ff df 4c 8d 34 dd 10 1d be 8d 4c 89 f0 <48> c1 e8 03 42 80 3c 38 00 74 08 4c 89 f7 e8 3c c0 7c 00 48 c7 c3
RSP: 0018:ffffc90002deed98 EFLAGS: 00000297
RAX: ffffffff8dbe1d18 RBX: 0000000000000001 RCX: 70220b63a5ae5d00
RDX: 0000000000000000 RSI: ffffffff8be33960 RDI: ffffffff8be33920
RBP: dffffc0000000000 R08: 0000000000000000 R09: ffffffff8172c195
R10: ffffc90002deeed8 R11: ffffffff81ac3ae0 R12: 1ffff920005bddd1
R13: ffffc90002deeec0 R14: ffffffff8dbe1d18 R15: dffffc0000000000
FS:  00007f6ca6d8e6c0(0000) GS:ffff8881a3c15000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000346030 CR3: 000000010f12a000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 unwind_next_frame+0xd4/0x2390
 arch_stack_walk+0x11c/0x150
 stack_trace_save+0x9c/0xe0
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_cache_noprof+0x230/0x3d0
 addr_event+0xc3/0x470
 inet6addr_event+0x9f/0xd0
 notifier_call_chain+0x1b6/0x3e0
 atomic_notifier_call_chain+0xda/0x180
 addrconf_ifdown+0xe76/0x1880
 addrconf_notify+0x1bc/0x1010
 notifier_call_chain+0x1b6/0x3e0
 netif_close_many+0x29c/0x410
 unregister_netdevice_many_notify+0x7b9/0x1ff0
 unregister_netdevice_queue+0x33c/0x380
 __tun_detach+0xda4/0x1560
 tun_chr_close+0x10a/0x1c0
 __fput+0x44c/0xa70
 task_work_run+0x1d4/0x260
 do_exit+0x6b5/0x2300
 do_group_exit+0x21c/0x2d0
 get_signal+0x1286/0x1340
 arch_do_signal_or_restart+0x9a/0x750
 exit_to_user_mode_loop+0x75/0x110
 do_syscall_64+0x2bd/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6ca5f9034a
Code: Unable to access opcode bytes at 0x7f6ca5f90320.
RSP: 002b:00007f6ca6d8de68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: 0000000000000000 RBX: 00007f6ca6d8def0 RCX: 00007f6ca5f9034a
RDX: 0000200000000040 RSI: 0000200000000000 RDI: 00007f6ca6d8deb0
RBP: 0000200000000040 R08: 00007f6ca6d8def0 R09: 0000000003800813
R10: 0000000003800813 R11: 0000000000000246 R12: 0000200000000000
R13: 00007f6ca6d8deb0 R14: 0000000000000a51 R15: 0000200000000140
 </TASK>
