INFO: task syz.6.217:7497 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.217       state:D stack:22760 pid:7497  tgid:7495  ppid:7344   task_flags:0x400140 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/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f429138ec29
RSP: 002b:00007f42922d2038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007f42915d5fa0 RCX: 00007f429138ec29
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f42915d5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f42915d6038 R14: 00007f42915d5fa0 R15: 00007ffd06822388
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/34:
 #0: ffffffff8e13a0e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
3 locks held by kworker/u10:9/1205:
 #0: ffff88801b314948 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc90007447bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffff88811b4c80e0 (&type->s_umount_key#53){++++}-{4:4}, at: super_trylock_shared+0x20/0xf0
2 locks held by getty/5673:
 #0: ffff8881098430a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900029062f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400
1 lock held by syz.4.166/7094:
 #0: ffff88811b4c8428 (sb_writers#14){.+.+}-{0:0}, at: vfs_write+0x211/0xb30
2 locks held by syz.6.217/7497:
 #0: ffff88811b4c80e0 (&type->s_umount_key#53){++++}-{4:4}, at: super_lock+0x2a9/0x3b0
 #1: ffff88811a0887d0 (&bdi->wb_switch_rwsem){+.+.}-{4:4}, at: sync_inodes_sb+0x19f/0xa10
2 locks held by syz.5.346/8598:
 #0: ffff88811b4c80e0 (&type->s_umount_key#53){++++}-{4:4}, at: super_lock+0x2a9/0x3b0
 #1: ffff88811a0887d0 (&bdi->wb_switch_rwsem){+.+.}-{4:4}, at: sync_inodes_sb+0x19f/0xa10
1 lock held by syz.4.514/10155:
 #0: ffff88811b4c80e0 (&type->s_umount_key#53){++++}-{4:4}, at: super_lock+0x25c/0x3b0
2 locks held by syz.3.554/10288:
 #0: ffff88802e430428 (sb_writers#3){.+.+}-{0:0}, at: direct_splice_actor+0x49/0x160
 #1: ffff88811b4c80e0 (&type->s_umount_key#53){++++}-{4:4}, at: super_lock+0x2a9/0x3b0
2 locks held by syz-executor/10515:
 #0: ffff88803a3cc0e0 (&type->s_umount_key#54){++++}-{4:4}, at: deactivate_super+0xa9/0xe0
 #1: ffffffff8e13fa40 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x4c/0x570
3 locks held by syz.6.697/11226:

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

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+0x189/0x250
 nmi_cpu_backtrace+0x39e/0x3d0
 nmi_trigger_cpumask_backtrace+0x17a/0x300
 watchdog+0xf93/0xfe0
 kthread+0x711/0x8a0
 ret_from_fork+0x439/0x7d0
 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: 5830 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:inet_recvmsg+0x11c/0x250
Code: 83 c7 70 4c 89 f8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 4c 89 ff e8 bc ed 1e f8 48 8d 44 24 40 4d 8b 3f <49> 81 ff 00 78 f1 89 0f 85 b3 00 00 00 49 89 c7 e8 2f 70 bb f7 4c
RSP: 0018:ffffc9000306fa60 EFLAGS: 00000246
RAX: ffffc9000306faa0 RBX: ffffc9000306fba0 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88810ab04100
RBP: ffffc9000306fb08 R08: ffff88810ab04100 R09: 0000000000000000
R10: ffffc9000306fbf8 R11: fffff5200060df81 R12: ffff88810ab04100
R13: 1ffff9200060df50 R14: 0000000000000040 R15: ffffffff89f17800
FS:  0000555577d71500(0000) GS:ffff8880b8613000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555647245c8 CR3: 00000001072ca000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 sock_recvmsg+0x1a8/0x270
 sock_read_iter+0x231/0x2f0
 vfs_read+0x55a/0xa30
 ksys_read+0x145/0x250
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff42518d5fd
Code: a8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb b5 e8 a8 48 00 00 0f 1f 84 00 00 00 00 00 80 3d 61 af 21 00 00 74 17 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 5b c3 66 2e 0f 1f 84 00 00 00 00 00 48 83 ec
RSP: 002b:00007fff96059898 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007ff42518d5fd
RDX: 0000000000000004 RSI: 00007fff960598ac RDI: 0000000000000003
RBP: 0000000000000000 R08: 000000002f18c322 R09: 7fffffffffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff96059cc0
R13: 0000000000000004 R14: 00007fff960598ac R15: 00007fff96059940
 </TASK>
