INFO: task syz.4.335:7938 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.335       state:D stack:28760 pid:7938  tgid:7937  ppid:5918   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x1821/0x5740
 schedule+0x164/0x360
 schedule_preempt_disabled+0x13/0x30
 rwsem_down_read_slowpath+0x6d9/0x940
 down_read+0x99/0x2e0
 super_lock+0x2d6/0x3d0
 __iterate_supers+0x126/0x250
 __ia32_sys_sync+0xa0/0x120
 do_syscall_64+0x15f/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb339f9cdd9
RSP: 002b:00007fb33ae8f028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007fb33a215fa0 RCX: 00007fb339f9cdd9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fb33a215fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb33a216038 R14: 00007fb33a215fa0 R15: 00007ffd2ad47648
 </TASK>
INFO: task syz.4.335:7940 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.335       state:D stack:28760 pid:7940  tgid:7937  ppid:5918   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x1821/0x5740
 schedule+0x164/0x360
 schedule_preempt_disabled+0x13/0x30
 rwsem_down_read_slowpath+0x6d9/0x940
 down_read+0x99/0x2e0
 super_lock+0x2d6/0x3d0
 __iterate_supers+0x126/0x250
 __ia32_sys_sync+0xa0/0x120
 do_syscall_64+0x15f/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb339f9cdd9
RSP: 002b:00007fb33ae6e028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007fb33a216090 RCX: 00007fb339f9cdd9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fb33a216090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb33a216128 R14: 00007fb33a216090 R15: 00007ffd2ad47648
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/34:
 #0: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by getty/5440:
 #0: ffff8881755680a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900034732e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45c/0x13a0
2 locks held by syz-executor/6525:
2 locks held by kworker/0:7/6605:
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860
 #1: ffffc900044afc40 (free_ipc_work){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860
2 locks held by syz-executor/7309:
1 lock held by syz.4.335/7938:
 #0: ffff8881b12f80d8 (&type->s_umount_key#66){++++}-{4:4}, at: super_lock+0x2d6/0x3d0
1 lock held by syz.4.335/7940:
 #0: ffff8881b12f80d8 (&type->s_umount_key#66){++++}-{4:4}, at: super_lock+0x2d6/0x3d0
2 locks held by syz-executor/7971:
 #0: ffff8881775620d8 (&type->s_umount_key#52){++++}-{4:4}, at: deactivate_super+0xa9/0xe0
 #1: ffffffff8edf8480 (jfs_log_mutex){+.+.}-{4:4}, at: lmLogClose+0xb4/0x520
1 lock held by syz.6.500/10898:
 #0: ffff8881b12f80d8 (&type->s_umount_key#66){++++}-{4:4}, at: super_lock+0x2d6/0x3d0
1 lock held by syz.6.500/10918:
 #0: ffff8881b12f80d8 (&type->s_umount_key#66){++++}-{4:4}, at: super_lock+0x2d6/0x3d0
2 locks held by syz-executor/11635:
 #0: ffff8881a9d2e0d8 (&type->s_umount_key#52){++++}-{4:4}, at: deactivate_super+0xa9/0xe0
 #1: ffffffff8edf8480 (jfs_log_mutex){+.+.}-{4:4}, at: lmLogClose+0xb4/0x520
1 lock held by syz.8.577/12774:
 #0: ffff88810980e0d8 (&type->s_umount_key#66){++++}-{4:4}, at: super_lock+0x2d6/0x3d0
2 locks held by syz-executor/12962:
 #0: ffff88816c8400d8 (&type->s_umount_key#52){++++}-{4:4}, at: deactivate_super+0xa9/0xe0
 #1: ffffffff8edf8480 (jfs_log_mutex){+.+.}-{4:4}, at: lmLogClose+0xb4/0x520
3 locks held by syz-executor/14335:
 #0: ffffffff8fdc13e8 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x4f7/0x730
 #1: ffffffff8fdd00c0 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x2a4/0x940
 #2: ffffffff8e963068 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x38d/0x770

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

NMI backtrace for cpu 1
CPU: 1 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+0xe8/0x150
 nmi_cpu_backtrace+0x274/0x2d0
 nmi_trigger_cpumask_backtrace+0x17a/0x300
 sys_info+0x135/0x170
 watchdog+0xfd3/0x1030
 kthread+0x388/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 14335 Comm: syz-executor 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:__lock_acquire+0x1968/0x2cf0
Code: 89 c1 81 e1 ff 0f 00 00 89 0d d8 39 a0 14 2b 05 ce 39 a0 14 25 ff 0f 00 00 39 05 8f 39 9f 12 73 06 89 05 87 39 9f 12 48 8b 02 <48> 89 df 4c 39 e8 0f 84 2c fe ff ff 4c 89 60 30 48 8b 00 4c 39 e8
RSP: 0018:ffffc900056febb0 EFLAGS: 00000002
RAX: ffffffff96d6eb68 RBX: 00000000000003fd RCX: 0000000000000457
RDX: ffffffff96d71f08 RSI: ffff88801c648c80 RDI: 00000000000003fd
RBP: 884bed8e84cda16f R08: ffffc900056feb78 R09: 0000000000000020
R10: dffffc0000000000 R11: ffffffff81a21f90 R12: ffffffff96db7418
R13: ffffffff93e91118 R14: ffff88801c648000 R15: 0000000000000456
FS:  0000555557fb7500(0000) GS:ffff88818dc8d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056107733ee38 CR3: 000000002197a000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 lock_acquire+0x106/0x350
 _raw_spin_lock+0x2e/0x40
 __hrtimer_rearm_deferred+0x99/0x450
 hrtick_schedule_exit+0x1c7/0x2b0
 __schedule+0x1dab/0x5740
 preempt_schedule_irq+0x4d/0xa0
 irqentry_exit+0x14f/0x760
 asm_sysvec_apic_timer_interrupt+0x1a/0x20
RIP: 0010:lock_acquire+0x221/0x350
Code: ff ff ff e8 e1 11 07 0a f7 44 24 08 00 02 00 00 0f 84 3a ff ff ff 65 48 8b 05 cb 7c 97 11 48 3b 44 24 58 75 33 fb 48 83 c4 60 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 48 8d 3d 58 61 92
RSP: 0018:ffffc900056ff178 EFLAGS: 00000286
RAX: 224646ca3a450000 RBX: 0000000000000000 RCX: 0000000000000046
RDX: 00000000fc8736c1 RSI: ffffffff8e219b45 RDI: ffffffff8c28af60
RBP: ffffffff8176f256 R08: ffffffff8176f256 R09: ffffffff8e95cd60
R10: ffffc900056ff2d8 R11: ffffffff81b0ebd0 R12: 0000000000000002
R13: ffffffff8e95cd60 R14: 0000000000000000 R15: 0000000000000246
 unwind_next_frame+0xc3/0x2550
 arch_stack_walk+0x11b/0x150
 stack_trace_save+0xa9/0x100
 kasan_save_stack+0x3e/0x60
 kasan_record_aux_stack+0xbd/0xd0
 call_rcu+0xee/0x890
 kernfs_put+0x259/0x520
 kernfs_remove_by_name_ns+0xc8/0x140
 sysfs_remove_group+0xfc/0x2e0
 sysfs_remove_groups+0x54/0xb0
 device_remove_attrs+0x229/0x280
 device_del+0x51f/0x8f0
 unregister_netdevice_many_notify+0x1d5f/0x22c0
 ops_undo_list+0x3d3/0x940
 setup_net+0x2f0/0x340
 copy_net_ns+0x50e/0x730
 create_new_namespaces+0x3e7/0x6a0
 unshare_nsproxy_namespaces+0x149/0x190
 ksys_unshare+0x57d/0x9f0
 __x64_sys_unshare+0x38/0x50
 do_syscall_64+0x15f/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd71339e0a7
Code: 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 10 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffff1f6d6e8 EFLAGS: 00000206 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007fd713615f40 RCX: 00007fd71339e0a7
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 00007fd7136167b8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000008
R13: 0000000000000003 R14: 00007ffff1f6d928 R15: 0000000000000000
 </TASK>
