INFO: task syz-executor1:32663 blocked for more than 120 seconds.
      Not tainted 4.9.108-gb7d377b #47
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor1   D26600 32663  30959 0x00000004
 ffff8801b798c800 ffff8801d0182a00 ffff8801cd46b480 ffff88019174b000
 ffff8801db221c18 ffff8801b66a7c10 ffffffff839e8aed ffff8801cd741188
 0000000000000000 0000000000000000 0000000000000000 ffff8801db2224e8
Call Trace:
 [<ffffffff839ea0ef>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839f4514>] rwsem_down_read_failed+0x1e4/0x320 kernel/locking/rwsem-xadd.c:260
 [<ffffffff81ee80d8>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<ffffffff839f3442>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<ffffffff839f3442>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<ffffffff8157cc61>] iterate_supers+0xe1/0x260 fs/super.c:591
 [<ffffffff8161aca2>] sys_sync+0xa2/0x170 fs/sync.c:112
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f99d3>] 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: [<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/3774:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7b92>] 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-executor1/32663:
 #0:  (&type->s_umount_key#51){++++..}, at: [<ffffffff8157cc61>] iterate_supers+0xe1/0x260 fs/super.c:591
1 lock held by syz-executor1/32681:
 #0:  (&type->s_umount_key#51){++++..}, at: [<ffffffff8157cc61>] iterate_supers+0xe1/0x260 fs/super.c:591

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

NMI backtrace for cpu 0
CPU: 0 PID: 520 Comm: khungtaskd Not tainted 4.9.108-gb7d377b #47
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8617d08 ffffffff81eb3e29 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b96a0 ffff8801d8617d40
 ffffffff81ebf127 0000000000000000 0000000000000000 0000000000000003
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
 [<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
 [<ffffffff839f9b9c>] 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: 32583 Comm: syz-executor0 Not tainted 4.9.108-gb7d377b #47
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff880184364800 task.stack: ffff8801b6fc8000
RIP: 0010:[<ffffffff8123ab28>] 
c [<ffffffff8123ab28>] lock_acquire+0x18/0x3e0 kernel/locking/lockdep.c:3745
RSP: 0018:ffff8801b6fcf5a8  EFLAGS: 00000246
RAX: dffffc0000000000 RBX: ffff8801b681abc8 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff846defa0
RBP: ffff8801b6fcf5b8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000007
R13: dffffc0000000000 R14: 0000000002420848 R15: 0000000000000002
FS:  00007f45e1a4e700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa88bb4e000 CR3: 00000001c9e4e000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000002420848
c ffff8801b681abc8
c ffff8801b6fcf620
c ffffffff81438afa
c
 ffffffff81438ab0
c ffffffff81623fd3
c ffff8801b681aa94
c 0000000000000000
c
 ffff8801b681a840
c 000000000000000f
c 0000000000000003
c 0000000000000007
c
Call Trace:
 [<ffffffff81438afa>] rcu_lock_acquire include/linux/rcupdate.h:493 [inline]
 [<ffffffff81438afa>] rcu_read_lock include/linux/rcupdate.h:875 [inline]
 [<ffffffff81438afa>] find_get_entry+0x4a/0x540 mm/filemap.c:1092
 [<ffffffff81439f2b>] pagecache_get_page+0x4b/0x720 mm/filemap.c:1203
 [<ffffffff816252a9>] find_or_create_page include/linux/pagemap.h:309 [inline]
 [<ffffffff816252a9>] grow_dev_page fs/buffer.c:1005 [inline]
 [<ffffffff816252a9>] grow_buffers fs/buffer.c:1078 [inline]
 [<ffffffff816252a9>] __getblk_slow fs/buffer.c:1105 [inline]
 [<ffffffff816252a9>] __getblk_gfp+0x249/0x710 fs/buffer.c:1386
 [<ffffffff81628b8d>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818b6db8>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818b6db8>] fat__get_entry+0x4c8/0x8f0 fs/fat/dir.c:100
 [<ffffffff818b9a41>] fat_get_entry fs/fat/dir.c:128 [inline]
 [<ffffffff818b9a41>] fat_get_short_entry+0x131/0x2a0 fs/fat/dir.c:876
 [<ffffffff818c19a7>] fat_subdirs+0xc7/0x190 fs/fat/dir.c:942
 [<ffffffff818d1cb9>] fat_read_root fs/fat/inode.c:1402 [inline]
 [<ffffffff818d1cb9>] fat_fill_super+0x1cf9/0x3550 fs/fat/inode.c:1832
 [<ffffffff818de00e>] msdos_fill_super+0x2e/0x40 fs/fat/namei_msdos.c:654
 [<ffffffff8157c3d7>] mount_bdev+0x2c7/0x390 fs/super.c:1100
 [<ffffffff818ddfd4>] msdos_mount+0x34/0x40 fs/fat/namei_msdos.c:661
 [<ffffffff8157e15c>] mount_fs+0x28c/0x370 fs/super.c:1206
 [<ffffffff815dd921>] vfs_kern_mount.part.29+0xd1/0x3d0 fs/namespace.c:991
 [<ffffffff815e5249>] vfs_kern_mount fs/namespace.c:973 [inline]
 [<ffffffff815e5249>] do_new_mount fs/namespace.c:2513 [inline]
 [<ffffffff815e5249>] do_mount+0x3c9/0x2740 fs/namespace.c:2835
 [<ffffffff815e7f9e>] SYSC_mount fs/namespace.c:3051 [inline]
 [<ffffffff815e7f9e>] SyS_mount+0xfe/0x110 fs/namespace.c:3028
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f99d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c