INFO: task syz.5.372:8010 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.372       state:D stack:28904 pid:8010  tgid:8008  ppid:7700   task_flags:0x400040 flags:0x00004004
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 wb_wait_for_completion+0x15f/0x260
 sync_inodes_sb+0x1bb/0xa10
 __iterate_supers+0x13d/0x290
 ksys_sync+0x94/0x150
 __ia32_sys_sync+0xe/0x20
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f026818eba9
RSP: 002b:00007f0268f8e038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007f02683d6090 RCX: 00007f026818eba9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f02683d6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f02683d6128 R14: 00007f02683d6090 R15: 00007fff66aa16c8
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/u10:0/27:
 #0: ffff888100083948 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc9000060fba0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: 
ffff8881246400e0 (&type->s_umount_key#72){++++}-{4:4}, at: super_trylock_shared+0x20/0xf0
1 lock held by khungtaskd/34:
 #0: ffffffff8e33c560 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by getty/5676:
 #0: ffff88802237b0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900027682f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400
1 lock held by syz.3.305/7470:
 #0: ffff888124640420 (sb_writers#25){.+.+}-{0:0}, at: vfs_writev+0x288/0x960
2 locks held by syz.5.372/8010:
 #0: ffff8881246400e0 (&type->s_umount_key#72){++++}-{4:4}, at: super_lock+0x2a9/0x3b0
 #1: ffff8881252507d0 (&bdi->wb_switch_rwsem){+.+.}-{4:4}, at: sync_inodes_sb+0x19f/0xa10
4 locks held by syz.4.924/11047:
1 lock held by syz.6.926/11089:
 #0: ffff888022b557e0 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x211/0x4d0
3 locks held by syz.6.926/11090:

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

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+0xf60/0xfa0
 kthread+0x711/0x8a0
 ret_from_fork+0x47f/0x820
 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: 11094 Comm: udevadm 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+0x55/0xb0
Code: 4d de 8d 4c 89 f0 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 f7 e8 9c 64 7d 00 48 c7 c3 98 1f c4 92 49 03 1e 48 89 d8 48 c1 e8 03 <42> 0f b6 04 38 84 c0 75 34 8b 03 65 ff 0d b9 a6 1c 11 74 11 83 e0
RSP: 0018:ffffc9000791f748 EFLAGS: 00000a06
RAX: 1ffff11026cc65f3 RBX: ffff888136632f98 RCX: 15e13ec661cc4c00
RDX: 0000000000000018 RSI: ffffffff8c035de0 RDI: ffffffff8c035da0
RBP: 0000000000002800 R08: 0000000000002800 R09: 00000000ffffffff
R10: ffff8881230488c0 R11: fffffbfff1f87907 R12: 00000000002d4800
R13: 0000000000000020 R14: ffffffff8dde4dd8 R15: dffffc0000000000
FS:  00007fa60a095c80(0000) GS:ffff8881a39f1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa60a141440 CR3: 0000000020464000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 trace_kmalloc+0x1f/0xd0
 __kmalloc_cache_noprof+0x3c5/0x6f0
 kmem_cache_free+0x171/0x690
 __put_anon_vma+0x12b/0x2d0
 unlink_anon_vmas+0x503/0x670
 free_pgtables+0x57a/0x9c0
 exit_mmap+0x43c/0xb40
 __mmput+0x118/0x430
 exit_mm+0x1da/0x2c0
 do_exit+0x648/0x2300
 do_group_exit+0x21c/0x2d0
 __x64_sys_exit_group+0x3f/0x40
 x64_sys_call+0x21f7/0x2200
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa609cfca90
Code: Unable to access opcode bytes at 0x7fa609cfca66.
RSP: 002b:00007fff55698f08 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fa609ded860 RCX: 00007fa609cfca90
RDX: 00000000000000e7 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00007fa609ded860 R08: 00007fff55698d40 R09: 00007fff55698e40
R10: 00007fff55698da0 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fa609df1658 R15: 0000000000000001
 </TASK>
