FAT-fs (loop7): Invalid FSINFO signature: 0x00000000, 0x00000000 (sector = 1)
INFO: task syz-executor2:3880 blocked for more than 140 seconds.
      Not tainted 4.9.112-gf540ce0 #8
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor2   D26760  3880      1 0x00000004
 ffff8801d94c3000 ffff8801baf8f480 ffff8801d49279c0 ffff8801b5776000
 ffff8801db221c18 ffff8801a0c07b40 ffffffff839e907d 0000000000000002
 0000000041b58ab3 ffffffff843bb23b 00ffffff81221570 ffff8801db2224e8
Call Trace:
 [<ffffffff839ea67f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff81602c29>] wb_wait_for_completion+0x149/0x1b0 fs/fs-writeback.c:221
 [<ffffffff81602e97>] __writeback_inodes_sb_nr+0x207/0x300 fs/fs-writeback.c:2310
 [<ffffffff81602fe7>] writeback_inodes_sb_nr fs/fs-writeback.c:2327 [inline]
 [<ffffffff81602fe7>] writeback_inodes_sb+0x27/0x30 fs/fs-writeback.c:2342
 [<ffffffff8161aba3>] __sync_filesystem fs/sync.c:35 [inline]
 [<ffffffff8161aba3>] sync_filesystem+0x93/0x240 fs/sync.c:63
 [<ffffffff81579635>] generic_shutdown_super+0x75/0x300 fs/super.c:423
 [<ffffffff81579f6f>] kill_block_super+0x9f/0x120 fs/super.c:1127
 [<ffffffff8157a2e5>] deactivate_locked_super+0x75/0xd0 fs/super.c:310
 [<ffffffff8157acf1>] deactivate_super+0x91/0xd0 fs/super.c:341
 [<ffffffff815dd032>] cleanup_mnt+0xb2/0x160 fs/namespace.c:1134
 [<ffffffff815dd166>] __cleanup_mnt+0x16/0x20 fs/namespace.c:1141
 [<ffffffff8119839c>] task_work_run+0x10c/0x180 kernel/task_work.c:116
 [<ffffffff8100559c>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161
 [<ffffffff810064d4>] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 [<ffffffff810064d4>] syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 [<ffffffff810064d4>] do_syscall_64+0x364/0x490 arch/x86/entry/common.c:287
 [<ffffffff839f9f53>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/520:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136675c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136675c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425de7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3776:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f8122>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211edc2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor2/3880:
 #0:  (&type->s_umount_key#45){++++..}, at: [<ffffffff8157ace9>] deactivate_super+0x89/0xd0 fs/super.c:340

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

NMI backtrace for cpu 1
CPU: 1 PID: 520 Comm: khungtaskd Not tainted 4.9.112-gf540ce0 #8
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d850fd08 ffffffff81eb3249 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9bd0 ffff8801d850fd40
 ffffffff81ebe547 0000000000000001 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81eb3249>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3249>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebe547>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebe4da>] 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
 [<ffffffff81366cf4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366cf4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366cf4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366cf4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0bd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa11c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 18841 Comm: kworker/u4:8 Not tainted 4.9.112-gf540ce0 #8
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn
c (flush-7:2)
c
task: ffff88019d1c8000 task.stack: ffff8801d5380000
RIP: 0010:[<ffffffff812365e3>] 
c [<ffffffff812365e3>] __lock_acquire+0x413/0x4070 kernel/locking/lockdep.c:3291
RSP: 0018:ffff8801d5387400  EFLAGS: 00000002
RAX: 0000000000000004 RBX: ffff88019d1c8940 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88019d1c8964
RBP: ffff8801d53875b0 R08: 0000000000000001 R09: 0000000000000000
R10: ffff88019d1c8000 R11: 1ffff10033a39127 R12: 00000000000001a3
R13: 0000000000000003 R14: ffff88019d1c88b4 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff019eff58 CR3: 00000001ca6be000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 0000000041b58ab3
c ffffffff843c3728
c ffffffff812361d0
c ffffffff81235667
c
 ffff88019d1c8000
c ffff88019d1c88c0
c 0000000600000007
c ffff88019d1c8000
c
 ffffffff839fa8e9
c ffff88019d1c8940
c ffffffff855b5160
c 0000000000000003
c
Call Trace:
 [<ffffffff8123acb0>] lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
 [<ffffffff839f9316>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
 [<ffffffff839f9316>] _raw_spin_lock+0x36/0x50 kernel/locking/spinlock.c:151
 [<ffffffff81623fa6>] spin_lock include/linux/spinlock.h:302 [inline]
 [<ffffffff81623fa6>] __find_get_block_slow+0xe6/0x330 fs/buffer.c:216
 [<ffffffff8162452e>] __find_get_block+0x23e/0x4c0 fs/buffer.c:1360
 [<ffffffff81625339>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff81625339>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff81628cdd>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818d68d1>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818d68d1>] fat_clusters_flush+0x111/0x380 fs/fat/misc.c:69
 [<ffffffff818d0862>] fat_write_inode+0xf2/0x170 fs/fat/inode.c:890
 [<ffffffff8160232d>] write_inode fs/fs-writeback.c:1180 [inline]
 [<ffffffff8160232d>] __writeback_single_inode+0x86d/0x1020 fs/fs-writeback.c:1379
 [<ffffffff8160362c>] writeback_sb_inodes+0x4ac/0xe70 fs/fs-writeback.c:1584
 [<ffffffff8160462f>] wb_writeback+0x2cf/0xbd0 fs/fs-writeback.c:1760
 [<ffffffff8160db5e>] wb_do_writeback fs/fs-writeback.c:1894 [inline]
 [<ffffffff8160db5e>] wb_workfn+0x20e/0xdb0 fs/fs-writeback.c:1930
 [<ffffffff8118d191>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df86>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d0bd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa11c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Code: 
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