INFO: task syz-executor0:6584 blocked for more than 140 seconds.
      Not tainted 4.9.123-g8dd3fc2 #27
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D28040  6584  21629 0x00000004
 ffff880196411800 0000000000000000 ffff8801d71a7480 ffff8801973c6000
 ffff8801db221c18 ffff8801a6b377f8 ffffffff839f0dbd ffff8801a6b37818
 ffff8801cbd0f028 0000000000000000 0000000000000000 ffff8801db2224e8
Call Trace:
 [<ffffffff839f23bf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839fd9f8>] __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:526 [inline]
 [<ffffffff839fd9f8>] rwsem_down_write_failed+0x598/0x990 kernel/locking/rwsem-xadd.c:555
 [<ffffffff81eed9a7>] call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105
 [<ffffffff839fb7cc>] __down_write arch/x86/include/asm/rwsem.h:125 [inline]
 [<ffffffff839fb7cc>] down_write+0x5c/0xa0 kernel/locking/rwsem.c:54
 [<ffffffff815a9625>] inode_lock include/linux/fs.h:766 [inline]
 [<ffffffff815a9625>] do_last fs/namei.c:3312 [inline]
 [<ffffffff815a9625>] path_openat+0xed5/0x3590 fs/namei.c:3534
 [<ffffffff815affa7>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff8157277d>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff81572aa0>] SYSC_openat fs/open.c:1099 [inline]
 [<ffffffff81572aa0>] SyS_openat+0x30/0x40 fs/open.c:1093
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a01c93>] 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: [<ffffffff81368a9c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81368a9c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81428308>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3776:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839ffe62>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff821253c2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor0/6584:
 #0:  (sb_writers#18){.+.+.+}, at: [<ffffffff815e516f>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#18){.+.+.+}, at: [<ffffffff815e516f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&sb->s_type->i_mutex_key#26){++++++}, at: [<ffffffff815a9625>] inode_lock include/linux/fs.h:766 [inline]
 #1:  (&sb->s_type->i_mutex_key#26){++++++}, at: [<ffffffff815a9625>] do_last fs/namei.c:3312 [inline]
 #1:  (&sb->s_type->i_mutex_key#26){++++++}, at: [<ffffffff815a9625>] path_openat+0xed5/0x3590 fs/namei.c:3534

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.123-g8dd3fc2 #27
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8567d08 ffffffff81eb9689 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9fa0 ffff8801d8567d40
 ffffffff81ec49c7 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb9689>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb9689>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ec49c7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ec495a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810ba0a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81369034>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81369034>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81369034>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81369034>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119f3cd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff83a01e5c>] 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: 6580 Comm: syz-executor0 Not tainted 4.9.123-g8dd3fc2 #27
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88019868b000 task.stack: ffff8801a6778000
RIP: 0010:[<ffffffff81238f0e>] 
c [<ffffffff81238f0e>] __lock_acquire+0xa9e/0x4070 kernel/locking/lockdep.c:3325
RSP: 0018:ffff8801a677ef10  EFLAGS: 00000046
RAX: dffffc0000000000 RBX: ffff88019868b940 RCX: 1ffff100330d172c
RDX: 1ffff100330d1717 RSI: ffff88019868b940 RDI: ffffffff8558e950
RBP: ffff8801a677f0c0 R08: ffff88019868b960 R09: 0000000000000000
R10: ffff88019868b000 R11: 1ffff100330d1727 R12: 0000000000000023
R13: 0000000000000003 R14: 0000000000000023 R15: 0000000000000000
FS:  00007fccaeba3700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3133c3e000 CR3: 000000019ccde000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffff8801a677ef60
c ffffffff81237907
c ffff8801a677ef40
c 0000000000000002
c
 ffff88019868b8c8
c ffffed00330d1718
c ffff88019868b000
c dffffc0000000000
c
 ffff8801a677efa0
c ffffffff81237907
c ffff8801a677ef80
c ffff88019868b8c0
c
Call Trace:
 [<ffffffff8123cf50>] lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
 [<ffffffff8143b1aa>] rcu_lock_acquire include/linux/rcupdate.h:493 [inline]
 [<ffffffff8143b1aa>] rcu_read_lock include/linux/rcupdate.h:875 [inline]
 [<ffffffff8143b1aa>] find_get_entry+0x4a/0x540 mm/filemap.c:1090
 [<ffffffff8143c5db>] pagecache_get_page+0x4b/0x720 mm/filemap.c:1201
 [<ffffffff816287d2>] find_get_page_flags include/linux/pagemap.h:264 [inline]
 [<ffffffff816287d2>] __find_get_block_slow+0xc2/0x330 fs/buffer.c:212
 [<ffffffff81628d7e>] __find_get_block+0x23e/0x4c0 fs/buffer.c:1360
 [<ffffffff81629b89>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff81629b89>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff8162d52d>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818bc718>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818bc718>] fat__get_entry+0x4c8/0x8f0 fs/fat/dir.c:100
 [<ffffffff818c4517>] fat_get_entry fs/fat/dir.c:128 [inline]
 [<ffffffff818c4517>] fat_search_long+0x277/0x1180 fs/fat/dir.c:477
 [<ffffffff818dea84>] vfat_find+0x134/0x180 fs/fat/namei_vfat.c:708
 [<ffffffff818df261>] vfat_lookup+0xe1/0x530 fs/fat/namei_vfat.c:731
 [<ffffffff8159f9dd>] lookup_open+0x63d/0x1930 fs/namei.c:3203
 [<ffffffff815a9648>] do_last fs/namei.c:3315 [inline]
 [<ffffffff815a9648>] path_openat+0xef8/0x3590 fs/namei.c:3534
 [<ffffffff815affa7>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff8157277d>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff81572aa0>] SYSC_openat fs/open.c:1099 [inline]
 [<ffffffff81572aa0>] SyS_openat+0x30/0x40 fs/open.c:1093
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a01c93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
cff 
c1f 
c00 
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c00 
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c49 
c8d 
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c08 
c00 
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c48 
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c44 
c24 
c70 
c48 
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c00 
c00 
c00 
c00 
c00 
cfc 
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cdf 
c48 
cc1 
cea 
c03 
c80 
c3c 
c02 
c00 
c<0f> 
c85 
c5c 
c28 
c00 
c00 
c45 
c85 
ced 
c4d 
c8b 
cba 
cb8 
c08 
c00 
c00 
c0f 
c85 
c2a 
cfc 
cff 
c