FAT-fs (loop2): Can't find a valid FAT filesystem
IPVS: Creating netns size=2536 id=42
INFO: task syz-executor6:16540 blocked for more than 140 seconds.
      Not tainted 4.9.118-g856452b #21
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor6   D28656 16540   3886 0x00000004
 ffff8801b57a3000 0000000000000000 ffff8801d4b2cfc0 ffff8801d9a6b000
 ffff8801db321c18 ffff8801cdee7ce8 ffffffff839ebbad ffff8801b57a38c8
 ffffed0036af4718 ffff8801b57a3000 00fffc0000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839ed1af>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839edb33>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586
 [<ffffffff839f1fb6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839f1fb6>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff815d853c>] __fdget_pos+0xac/0xd0 fs/file.c:781
 [<ffffffff81576bce>] fdget_pos include/linux/file.h:66 [inline]
 [<ffffffff81576bce>] SYSC_write fs/read_write.c:599 [inline]
 [<ffffffff81576bce>] SyS_write+0x7e/0x1c0 fs/read_write.c:596
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fca93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/519:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136679c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136679c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.?..}, at: [<ffffffff81425fb7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by rs:main Q:Reg/3679:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d853c>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff8157301e>] file_start_write include/linux/fs.h:2640 [inline]
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff8157301e>] vfs_write+0x3ae/0x530 fs/read_write.c:556
2 locks held by getty/3777:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839fac52>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff821207a2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor6/16451:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d853c>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #1:  (sb_writers#11){.+.+.+}, at: [<ffffffff8157301e>] file_start_write include/linux/fs.h:2640 [inline]
 #1:  (sb_writers#11){.+.+.+}, at: [<ffffffff8157301e>] vfs_write+0x3ae/0x530 fs/read_write.c:556
1 lock held by syz-executor6/16539:
 #0:  (sb_writers#11){.+.+.+}, at: [<ffffffff815e0ddf>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#11){.+.+.+}, at: [<ffffffff815e0ddf>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
1 lock held by syz-executor6/16540:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d853c>] __fdget_pos+0xac/0xd0 fs/file.c:781

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.118-g856452b #21
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d85e7d08 ffffffff81eb4b89 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9bd0 ffff8801d85e7d40
 ffffffff81ebfe87 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb4b89>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4b89>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebfe87>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebfe1a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9cd4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366d34>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366d34>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366d34>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366d34>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fcc5c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff839fb6b6