FAT-fs (loop6): Can't find a valid FAT filesystem
FAT-fs (loop6): Unrecognized mount option "security" or missing value
INFO: task syz-executor0:7962 blocked for more than 120 seconds.
      Not tainted 4.9.109-g7cecc75 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D27976  7962      1 0x00000002
 ffff8801d41f4800 ffff8801b6c98540 ffff8801ccaacfc0 ffff8801cb2bc800
 ffff8801db221c18 ffff8801b887f9d8 ffffffff839e8a3d ffffffff812355f7
 0000000000000000 ffff8801d41f50c0 0000000600000007 ffff8801db2224e8
Call Trace:
 [<ffffffff839ea03f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839f5678>] __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:526 [inline]
 [<ffffffff839f5678>] rwsem_down_write_failed+0x598/0x990 kernel/locking/rwsem-xadd.c:555
 [<ffffffff81ee8107>] call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105
 [<ffffffff839f344c>] __down_write arch/x86/include/asm/rwsem.h:125 [inline]
 [<ffffffff839f344c>] down_write+0x5c/0xa0 kernel/locking/rwsem.c:54
 [<ffffffff8157ab99>] deactivate_super+0x89/0xd0 fs/super.c:340
 [<ffffffff815dcee2>] cleanup_mnt+0xb2/0x160 fs/namespace.c:1134
 [<ffffffff815dd016>] __cleanup_mnt+0x16/0x20 fs/namespace.c:1141
 [<ffffffff8119832c>] task_work_run+0x10c/0x180 kernel/task_work.c:116
 [<ffffffff81140e41>] exit_task_work include/linux/task_work.h:21 [inline]
 [<ffffffff81140e41>] do_exit+0x9e1/0x27c0 kernel/exit.c:837
 [<ffffffff81146f41>] do_group_exit+0x111/0x340 kernel/exit.c:941
 [<ffffffff8114718d>] SYSC_exit_group kernel/exit.c:952 [inline]
 [<ffffffff8114718d>] SyS_exit_group+0x1d/0x20 kernel/exit.c:950
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9913>] 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: [<ffffffff8136662c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136662c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.?..}, at: [<ffffffff81425cb7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3777:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7ae2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211fce2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor0/7962:
 #0:  (&type->s_umount_key#35){++++..}, at: [<ffffffff8157ab99>] deactivate_super+0x89/0xd0 fs/super.c:340
1 lock held by syz-executor4/16115:
 #0:  (&type->s_umount_key#35){++++..}, at: [<ffffffff8157cc61>] iterate_supers+0xe1/0x260 fs/super.c:591
1 lock held by syz-executor4/16183:
 #0:  (&type->s_umount_key#35){++++..}, at: [<ffffffff8157cc61>] iterate_supers+0xe1/0x260 fs/super.c:591

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.109-g7cecc75 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8617d08 ffffffff81eb3e29 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9580 ffff8801d8617d40
 ffffffff81ebf127 0000000000000000 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81eb3e29>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3e29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebf127>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebf0ba>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9684>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366bc4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366bc4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366bc4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366bc4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9adc>] 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
CPU: 1 PID: 19262 Comm: kworker/u4:10 Not tainted 4.9.109-g7cecc75 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn
c (flush-7:0)
c
task: ffff8801cbbcb000 task.stack: ffff8801b6e88000
RIP: 0010:[<ffffffff812301be>] 
c [<ffffffff812301be>] __lock_is_held+0x8e/0xf0 kernel/locking/lockdep.c:3594
RSP: 0018:ffff8801b6e8f4b8  EFLAGS: 00000006
RAX: 0000000000000000 RBX: ffff8801cbbcb000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff846defa0 RDI: ffff8801cbbcb912
RBP: ffff8801b6e8f4e8 R08: ffff8801cbbcb988 R09: 0000000000000001
R10: ffff8801cbbcb000 R11: 1ffff1003977972c R12: ffffed0039779718
R13: ffff8801cbbcb8c8 R14: ffffffff846defa0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c4556ad000 CR3: 00000001c3354000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffff8801cbbcb8c0
c 0000000000000246
c ffff8801cbbcb000
c ffffffff846defa0
c
 0000000000000000
c ffff8801cbfe6548
c ffff8801b6e8f510
c ffffffff81230a04
c
 ffffea00070c4b80
c ffff88016c168b30
c dffffc0000000000
c ffff8801b6e8f520
c
Call Trace:
 [<ffffffff81230a04>] lock_is_held+0xb4/0x140 kernel/locking/lockdep.c:3794
 [<ffffffff8127c114>] rcu_read_lock_held+0xa4/0xc0 kernel/rcu/update.c:297
 [<ffffffff81438dfb>] radix_tree_deref_slot include/linux/radix-tree.h:199 [inline]
 [<ffffffff81438dfb>] find_get_entry+0x34b/0x540 mm/filemap.c:1097
 [<ffffffff81439f2b>] pagecache_get_page+0x4b/0x720 mm/filemap.c:1203
 [<ffffffff81623e32>] find_get_page_flags include/linux/pagemap.h:264 [inline]
 [<ffffffff81623e32>] __find_get_block_slow+0xc2/0x330 fs/buffer.c:212
 [<ffffffff816243de>] __find_get_block+0x23e/0x4c0 fs/buffer.c:1360
 [<ffffffff816251e9>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff816251e9>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff81628b8d>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818d5dd1>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818d5dd1>] fat_clusters_flush+0x111/0x380 fs/fat/misc.c:69
 [<ffffffff818cfd62>] fat_write_inode+0xf2/0x170 fs/fat/inode.c:890
 [<ffffffff816021dd>] write_inode fs/fs-writeback.c:1180 [inline]
 [<ffffffff816021dd>] __writeback_single_inode+0x86d/0x1020 fs/fs-writeback.c:1379
 [<ffffffff816034dc>] writeback_sb_inodes+0x4ac/0xe70 fs/fs-writeback.c:1584
 [<ffffffff81603f9b>] __writeback_inodes_wb+0xfb/0x1e0 fs/fs-writeback.c:1653
 [<ffffffff81604722>] wb_writeback+0x512/0xbd0 fs/fs-writeback.c:1762
 [<ffffffff8160e050>] wb_check_old_data_flush fs/fs-writeback.c:1877 [inline]
 [<ffffffff8160e050>] wb_do_writeback fs/fs-writeback.c:1901 [inline]
 [<ffffffff8160e050>] wb_workfn+0x850/0xdb0 fs/fs-writeback.c:1930
 [<ffffffff8118d121>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df16>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9adc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Code: 
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