INFO: task syz-executor7:22487 blocked for more than 140 seconds.
      Not tainted 4.9.119-g9dc978d #23
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor7   D26280 22487      1 0x00000004
 ffff8801d920e000 0000000000000000 ffff880198c24a80 ffff8801d9a6b000
 ffff8801db321c18 ffff8801a53bf4c8 ffffffff839ebdcd ffff8801d920e8c8
 ffffed003b241d18 ffff8801d920e000 00fffc0000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839ed3cf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839edd53>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586
 [<ffffffff839f21d6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839f21d6>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff818da421>] vfat_lookup+0xd1/0x530 fs/fat/namei_vfat.c:729
 [<ffffffff8159515e>] lookup_slow+0x23e/0x470 fs/namei.c:1668
 [<ffffffff815a16e6>] walk_component+0x716/0x1bb0 fs/namei.c:1784
 [<ffffffff815a3409>] link_path_walk+0x889/0x1200 fs/namei.c:2120
 [<ffffffff815a447d>] path_openat+0x1ad/0x3590 fs/namei.c:3533
 [<ffffffff815abb27>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff8156e2fd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff8156e5dd>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff8156e5dd>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fccd3>] 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: [<ffffffff813667bc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813667bc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.?..}, at: [<ffffffff81426027>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3550:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839fae72>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff821208d2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor7/22487:
 #0:  (&sb->s_type->i_mutex_key#24){++++++}, at: [<ffffffff81595061>] inode_lock_shared include/linux/fs.h:776 [inline]
 #0:  (&sb->s_type->i_mutex_key#24){++++++}, at: [<ffffffff81595061>] lookup_slow+0x141/0x470 fs/namei.c:1645
 #1:  (&sbi->s_lock){+.+.+.}, at: [<ffffffff818da421>] vfat_lookup+0xd1/0x530 fs/fat/namei_vfat.c:729
3 locks held by syz-executor7/18195:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d859c>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #1:  (&sb->s_type->i_mutex_key#24){++++++}, at: [<ffffffff815b4213>] inode_lock_shared include/linux/fs.h:776 [inline]
 #1:  (&sb->s_type->i_mutex_key#24){++++++}, at: [<ffffffff815b4213>] iterate_dir+0xc3/0x600 fs/readdir.c:39
 #2:  (&sbi->s_lock){+.+.+.}, at: [<ffffffff818c07a7>] __fat_readdir+0x1b7/0x1840 fs/fat/dir.c:570

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.119-g9dc978d #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d861fd08 ffffffff81eb4be9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9bd0 ffff8801d861fd40
 ffffffff81ebfee7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb4be9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebfee7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebfe7a>] 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
 [<ffffffff81366d54>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366d54>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366d54>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366d54>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fce9c>] 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: 18181 Comm: syz-executor7 Not tainted 4.9.119-g9dc978d #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff880198ec9800 task.stack: ffff8801cce38000
RIP: 0010:[<ffffffff8123564e>] 
c [<ffffffff8123564e>] mark_held_locks+0xee/0x130 kernel/locking/lockdep.c:2665
RSP: 0018:ffff8801cce3f7f0  EFLAGS: 00000086
RAX: 0000000000000001 RBX: ffff880198ec9800 RCX: 1ffff100331d9427
RDX: 1ffffffff0ac0bc6 RSI: ffff880198eca118 RDI: ffffffff85605e30
RBP: ffff8801cce3f810 R08: ffff880198eca138 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff880198eca0c8
R13: ffffed00331d9418 R14: ffff880198ec9800 R15: dffffc0000000000
FS:  00007f2047220700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000707914 CR3: 00000001a3a4e000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 00000000200001c0 DR2: 0000000020000000
DR3: 0000000020000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffffffff81624883
c dffffc0000000000
c ffff880194e0ba80
c 000000000000000f
c
 ffff8801cce3f830
c ffffffff812358f6
c 0000000000000010
c 0000000000000000
c
 ffff8801cce3f840
c ffffffff81235c2d
c ffff8801cce3f890
c ffffffff81624883
c
Call Trace:
 [<ffffffff812358f6>] __trace_hardirqs_on_caller kernel/locking/lockdep.c:2681 [inline]
 [<ffffffff812358f6>] trace_hardirqs_on_caller+0x266/0x590 kernel/locking/lockdep.c:2736
 [<ffffffff81235c2d>] trace_hardirqs_on+0xd/0x10 kernel/locking/lockdep.c:2743
 [<ffffffff81624883>] lookup_bh_lru fs/buffer.c:1344 [inline]
 [<ffffffff81624883>] __find_get_block+0x183/0x4c0 fs/buffer.c:1356
 [<ffffffff81625749>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff81625749>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff816290ed>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818b78e8>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818b78e8>] fat__get_entry+0x4c8/0x8f0 fs/fat/dir.c:100
 [<ffffffff818c095c>] fat_get_entry fs/fat/dir.c:128 [inline]
 [<ffffffff818c095c>] __fat_readdir+0x36c/0x1840 fs/fat/dir.c:589
 [<ffffffff818c1e71>] fat_readdir+0x41/0x50 fs/fat/dir.c:703
 [<ffffffff815b42fc>] iterate_dir+0x1ac/0x600 fs/readdir.c:50
 [<ffffffff815b533c>] SYSC_getdents fs/readdir.c:230 [inline]
 [<ffffffff815b533c>] SyS_getdents+0x13c/0x2a0 fs/readdir.c:211
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fccd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
cb9 
cec 
cff 
cff 
c85 
cc0 
c74 
c1e 
c41 
c0f 
cb6 
c45 
c00 
c83 
cc3 
c01 
c84 
cc0 
c74 
c04 
c3c 
c03 
c7e 
c40 
c41 
c39 
c9e 
cc0 
c08 
c00 
c00 
c7f 
ca1 
cb8 
c01 
c00 
c00 
c00 
c48 
c83 
cc4 
c18 
c5b 
c<41> 
c5c 
c41 
c5d 
c41 
c5e 
c41 
c5f 
c5d 
cc3 
c48 
c8b 
c7d 
cc8 
c89 
c75 
cd4 
ce8 
c7c 
c68 
c30 
c