INFO: task syz-executor6:30671 blocked for more than 120 seconds.
      Not tainted 4.9.107-gdb2c520 #46
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor6   D28416 30671   8147 0x00000004
 ffff8801c119b000 ffff8801870c5f80 ffff8801cc454540 ffff8801ce163000
 ffff8801db221c18 ffff8801d86d7c10 ffffffff839e8c1d ffffffff812355f7
 0000000000000000 ffff8801c119b8c0 0000000600000007 ffff8801db2224e8
Call Trace:
 [<ffffffff839ea21f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839f4644>] rwsem_down_read_failed+0x1e4/0x320 kernel/locking/rwsem-xadd.c:260
 [<ffffffff81ee8058>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<ffffffff839f3572>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<ffffffff839f3572>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<ffffffff8157cbd1>] iterate_supers+0xe1/0x260 fs/super.c:591
 [<ffffffff8161ac12>] sys_sync+0xa2/0x170 fs/sync.c:112
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9b13>] 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/3771:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7cc2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211fc62>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor6/30671:
 #0:  (&type->s_umount_key#34){++++..}, at: [<ffffffff8157cbd1>] iterate_supers+0xe1/0x260 fs/super.c:591
1 lock held by syz-executor6/30702:
 #0:  (&type->s_umount_key#34){++++..}, at: [<ffffffff8157cbd1>] iterate_supers+0xe1/0x260 fs/super.c:591

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.107-gdb2c520 #46
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d84e7d08 ffffffff81eb3da9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b96a0 ffff8801d84e7d40
 ffffffff81ebf0a7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb3da9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3da9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebf0a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebf03a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b97a4>] 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
 [<ffffffff839f9cdc>] 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: 30640 Comm: syz-executor0 Not tainted 4.9.107-gdb2c520 #46
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d57fc800 task.stack: ffff8801d8860000
RIP: 0010:[<ffffffff811bb361>] 
c [<ffffffff811bb361>] ___might_sleep+0x31/0x260 kernel/sched/core.c:7958
RSP: 0018:ffff8801d88675b8  EFLAGS: 00000246
RAX: 0000000000000001 RBX: ffff8801d57fc800 RCX: ffffc900044b0000
RDX: 0000000000000000 RSI: ffffffff846def60 RDI: ffff8801d57fd0c4
RBP: ffff8801d88675e0 R08: ffff8801d57fd110 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffff1003aaffa1d R12: 0000000000000000
R13: ffffffff83ca4920 R14: 00000000000001c4 R15: ffff8801d9c16b08
FS:  00007f48711c6700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000703914 CR3: 00000001961e6000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffff8801d57fc800
c ffffffff83ca4920
c 00000000000001c4
c 0000000000000000
c
 ffff8801d9c16b08
c ffff8801d8867620
c ffffffff811bb625
c ffffea00072c35c0
c
 0000000000000003
c ffffea00072c35c0
c 0000000000000007
c dffffc0000000000
c
Call Trace:
 [<ffffffff811bb625>] __might_sleep+0x95/0x1a0 kernel/sched/core.c:7949
 [<ffffffff8143a29d>] lock_page include/linux/pagemap.h:452 [inline]
 [<ffffffff8143a29d>] pagecache_get_page+0x3bd/0x720 mm/filemap.c:1216
 [<ffffffff81625219>] find_or_create_page include/linux/pagemap.h:309 [inline]
 [<ffffffff81625219>] grow_dev_page fs/buffer.c:1005 [inline]
 [<ffffffff81625219>] grow_buffers fs/buffer.c:1078 [inline]
 [<ffffffff81625219>] __getblk_slow fs/buffer.c:1105 [inline]
 [<ffffffff81625219>] __getblk_gfp+0x249/0x710 fs/buffer.c:1386
 [<ffffffff81628afd>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818b6d28>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818b6d28>] fat__get_entry+0x4c8/0x8f0 fs/fat/dir.c:100
 [<ffffffff818b99b1>] fat_get_entry fs/fat/dir.c:128 [inline]
 [<ffffffff818b99b1>] fat_get_short_entry+0x131/0x2a0 fs/fat/dir.c:876
 [<ffffffff818c1917>] fat_subdirs+0xc7/0x190 fs/fat/dir.c:942
 [<ffffffff818d1c29>] fat_read_root fs/fat/inode.c:1402 [inline]
 [<ffffffff818d1c29>] fat_fill_super+0x1cf9/0x3550 fs/fat/inode.c:1832
 [<ffffffff818d89e1>] vfat_fill_super+0x31/0x40 fs/fat/namei_vfat.c:1070
 [<ffffffff8157c347>] mount_bdev+0x2c7/0x390 fs/super.c:1100
 [<ffffffff818d89a4>] vfat_mount+0x34/0x40 fs/fat/namei_vfat.c:1077
 [<ffffffff8157e0cc>] mount_fs+0x28c/0x370 fs/super.c:1206
 [<ffffffff815dd891>] vfs_kern_mount.part.29+0xd1/0x3d0 fs/namespace.c:991
 [<ffffffff815e51b9>] vfs_kern_mount fs/namespace.c:973 [inline]
 [<ffffffff815e51b9>] do_new_mount fs/namespace.c:2513 [inline]
 [<ffffffff815e51b9>] do_mount+0x3c9/0x2740 fs/namespace.c:2835
 [<ffffffff815e7f0e>] SYSC_mount fs/namespace.c:3051 [inline]
 [<ffffffff815e7f0e>] SyS_mount+0xfe/0x110 fs/namespace.c:3028
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9b13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c