FAT-fs (loop5): bogus number of reserved sectors
FAT-fs (loop5): Can't find a valid FAT filesystem
INFO: task syz-executor7:11286 blocked for more than 140 seconds.
      Not tainted 4.9.113-g47bbcd6 #10
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor7   D29512 11286   3866 0x00000004
 ffff8801d9988000 0000000000000000 ffff8801bb56f480 ffff8801b8634800
 ffff8801db221c18 ffff880199cbfb58 ffffffff839e909d 0000000000000002
 0000000041b58ab3 ffffffff843bbae3 00ffffff81221550 ffff8801db2224e8
Call Trace:
 [<ffffffff839ea69f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff81602c89>] wb_wait_for_completion+0x149/0x1b0 fs/fs-writeback.c:221
 [<ffffffff81608419>] sync_inodes_sb+0x1a9/0x8d0 fs/fs-writeback.c:2412
 [<ffffffff8161a543>] sync_inodes_one_sb+0x43/0x60 fs/sync.c:73
 [<ffffffff8157ce00>] iterate_supers+0x130/0x260 fs/super.c:593
 [<ffffffff8161ae52>] sys_sync+0xa2/0x170 fs/sync.c:112
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9f93>] 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: [<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 rs:main Q:Reg/3672:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d81ec>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff81572cce>] file_start_write include/linux/fs.h:2640 [inline]
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff81572cce>] vfs_write+0x3ae/0x530 fs/read_write.c:556
2 locks held by getty/3771:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f8142>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211ee22>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor7/11286:
 #0:  (&type->s_umount_key#43){++++..}, at: [<ffffffff8157cdb1>] iterate_supers+0xe1/0x260 fs/super.c:591
1 lock held by syz-executor7/11327:
 #0:  (&type->s_umount_key#43){++++..}, at: [<ffffffff8157cdb1>] iterate_supers+0xe1/0x260 fs/super.c:591

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d962fd08 ffffffff81eb32a9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9bd0 ffff8801d962fd40
 ffffffff81ebe5a7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb32a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb32a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebe5a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebe53a>] 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
 [<ffffffff8119d0ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa15c>] 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: 4118 Comm: kworker/u4:4 Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn
c (flush-7:6)
c
task: ffff88019e48c800 task.stack: ffff8801d7948000
RIP: 0010:[<ffffffff8123018f>] 
c [<ffffffff8123018f>] __lock_is_held+0xf/0xf0 kernel/locking/lockdep.c:3590
RSP: 0018:ffff8801d794f4b8  EFLAGS: 00000046
RAX: 0000000000000007 RBX: 0000000000000246 RCX: ffff88019e48c800
RDX: 0000000000000000 RSI: 00000000000001c4 RDI: ffffffff846def60
RBP: ffff8801d794f4d8 R08: ffff88019e48d160 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffff10033c91a27 R12: ffff88019e48c800
R13: ffffffff846def60 R14: ffffffff846def60 R15: ffff8801d6196b08
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4e221c1000 CR3: 00000001bec44000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffff88019e48c800
c ffffffff846def60
c 00000000000001c4
c ffff8801d6196b08
c
 ffff8801d794f500
c ffffffff81230a54
c ffff88019e48c800
c 0000000000000000
c
 ffffffff83ca47a0
c ffff8801d794f538
c ffffffff811bb58f
c ffff88019e48c800
c
Call Trace:
 [<ffffffff81230a54>] lock_is_held+0xb4/0x140 kernel/locking/lockdep.c:3794
 [<ffffffff811bb58f>] ___might_sleep+0x1ff/0x260 kernel/sched/core.c:7954
 [<ffffffff811bb685>] __might_sleep+0x95/0x1a0 kernel/sched/core.c:7945
 [<ffffffff8143a3cd>] lock_page include/linux/pagemap.h:452 [inline]
 [<ffffffff8143a3cd>] pagecache_get_page+0x3bd/0x720 mm/filemap.c:1216
 [<ffffffff81625459>] find_or_create_page include/linux/pagemap.h:309 [inline]
 [<ffffffff81625459>] grow_dev_page fs/buffer.c:1005 [inline]
 [<ffffffff81625459>] grow_buffers fs/buffer.c:1078 [inline]
 [<ffffffff81625459>] __getblk_slow fs/buffer.c:1105 [inline]
 [<ffffffff81625459>] __getblk_gfp+0x249/0x710 fs/buffer.c:1386
 [<ffffffff81628d3d>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818cc63b>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818cc63b>] __fat_write_inode+0x2ab/0x980 fs/fat/inode.c:844
 [<ffffffff818d0849>] fat_write_inode+0x79/0x170 fs/fat/inode.c:893
 [<ffffffff8160238d>] write_inode fs/fs-writeback.c:1180 [inline]
 [<ffffffff8160238d>] __writeback_single_inode+0x86d/0x1020 fs/fs-writeback.c:1379
 [<ffffffff8160368c>] writeback_sb_inodes+0x4ac/0xe70 fs/fs-writeback.c:1584
 [<ffffffff8160414b>] __writeback_inodes_wb+0xfb/0x1e0 fs/fs-writeback.c:1653
 [<ffffffff816048d2>] wb_writeback+0x512/0xbd0 fs/fs-writeback.c:1762
 [<ffffffff8160dbbe>] wb_do_writeback fs/fs-writeback.c:1894 [inline]
 [<ffffffff8160dbbe>] wb_workfn+0x20e/0xdb0 fs/fs-writeback.c:1930
 [<ffffffff8118d181>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df76>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d0ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa15c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Code: 
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