INFO: task syz-executor0:18526 blocked for more than 140 seconds.
      Not tainted 4.9.124-g09eb2ba #31
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D27864 18526      1 0x00000004
 ffff8801991f0000 0000000000000000 ffff8801c29c0000 ffffffff84629800
 ffff8801db221c18 ffff8801bd86f4c8 ffffffff839f0afd ffff8801991f08c8
 ffffed003323e118 ffff8801991f0000 00fffc0000000000 ffff8801db2224e8
Call Trace:
 [<ffffffff839f20ff>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839f2a83>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586
 [<ffffffff839f6f06>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839f6f06>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff818df1b1>] vfat_lookup+0xd1/0x530 fs/fat/namei_vfat.c:729
 [<ffffffff8159953e>] lookup_slow+0x23e/0x470 fs/namei.c:1668
 [<ffffffff815a5ac6>] walk_component+0x716/0x1bb0 fs/namei.c:1784
 [<ffffffff815a77e9>] link_path_walk+0x889/0x1200 fs/namei.c:2120
 [<ffffffff815a885d>] path_openat+0x1ad/0x3590 fs/namei.c:3533
 [<ffffffff815aff07>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff815726dd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff815729bd>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff815729bd>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] 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: [<ffffffff813689dc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813689dc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81428248>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3722:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839ffba2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82125402>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor0/18526:
 #0:  (&sb->s_type->i_mutex_key#20){++++++}, at: [<ffffffff81599441>] inode_lock_shared include/linux/fs.h:776 [inline]
 #0:  (&sb->s_type->i_mutex_key#20){++++++}, at: [<ffffffff81599441>] lookup_slow+0x141/0x470 fs/namei.c:1645
 #1:  (&sbi->s_lock){+.+.+.}, at: [<ffffffff818df1b1>] vfat_lookup+0xd1/0x530 fs/fat/namei_vfat.c:729
1 lock held by syz-executor0/19353:
 #0:  (&sb->s_type->i_mutex_key#20){++++++}, at: [<ffffffff81599441>] inode_lock_shared include/linux/fs.h:776 [inline]
 #0:  (&sb->s_type->i_mutex_key#20){++++++}, at: [<ffffffff81599441>] lookup_slow+0x141/0x470 fs/namei.c:1645

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d84f7d08 ffffffff81eb95e9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9fa0 ffff8801d84f7d40
 ffffffff81ec4927 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb95e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb95e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ec4927>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ec48ba>] 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
 [<ffffffff81368f74>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81368f74>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81368f74>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81368f74>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119f3cd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff83a01b9c>] 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: 19292 Comm: syz-executor0 Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88018da4c800 task.stack: ffff8801a5678000
RIP: 0010:[<ffffffff81360d2f>] 
c [<ffffffff81360d2f>] __sanitizer_cov_trace_pc+0x3f/0x50 kernel/kcov.c:105
RSP: 0018:ffff8801a567ef88  EFLAGS: 00000216
RAX: 0000000000040000 RBX: 0000000000000001 RCX: ffffc900116cc000
RDX: 0000000000040000 RSI: ffffffff81f211a9 RDI: ffff88018da4da00
RBP: ffff8801a567ef88 R08: ffff88018da4d138 R09: 0000000000000001
R10: ffff88018da4c800 R11: 1ffff10031b49a22 R12: ffff88018fc6fce8
R13: dffffc0000000000 R14: 0000000002420848 R15: ffff8801d619a608
FS:  00007f4a96b6d700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1689ff9000 CR3: 00000001a9cb8000 CR4: 00000000001606f0
Stack:
 ffff8801a567ef98
c ffffffff81f211a9
c ffff8801a567efc8
c ffffffff812863ec
c
 ffff8801a567efc8
c ffffea0006e50100
c ffff88018fc6fce8
c dffffc0000000000
c
 ffff8801a567efd8
c ffffffff8127e450
c ffff8801a567f040
c ffffffff8143b3db
c
Call Trace:
 [<ffffffff81f211a9>] debug_smp_processor_id+0x9/0x20 lib/smp_processor_id.c:56
 [<ffffffff812863ec>] rcu_lockdep_current_cpu_online+0x3c/0x140 kernel/rcu/tree.c:1105
 [<ffffffff8127e450>] rcu_read_lock_held+0x90/0xc0 kernel/rcu/update.c:295
 [<ffffffff8143b3db>] radix_tree_deref_slot include/linux/radix-tree.h:199 [inline]
 [<ffffffff8143b3db>] find_get_entry+0x34b/0x540 mm/filemap.c:1095
 [<ffffffff8143c50b>] pagecache_get_page+0x4b/0x720 mm/filemap.c:1201
 [<ffffffff81629ba9>] find_or_create_page include/linux/pagemap.h:309 [inline]
 [<ffffffff81629ba9>] grow_dev_page fs/buffer.c:1005 [inline]
 [<ffffffff81629ba9>] grow_buffers fs/buffer.c:1078 [inline]
 [<ffffffff81629ba9>] __getblk_slow fs/buffer.c:1105 [inline]
 [<ffffffff81629ba9>] __getblk_gfp+0x249/0x710 fs/buffer.c:1386
 [<ffffffff8162d48d>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818bc678>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818bc678>] fat__get_entry+0x4c8/0x8f0 fs/fat/dir.c:100
 [<ffffffff818c4477>] fat_get_entry fs/fat/dir.c:128 [inline]
 [<ffffffff818c4477>] fat_search_long+0x277/0x1180 fs/fat/dir.c:477
 [<ffffffff818de9e4>] vfat_find+0x134/0x180 fs/fat/namei_vfat.c:708
 [<ffffffff818df1c1>] vfat_lookup+0xe1/0x530 fs/fat/namei_vfat.c:731
 [<ffffffff8159953e>] lookup_slow+0x23e/0x470 fs/namei.c:1668
 [<ffffffff815a5ac6>] walk_component+0x716/0x1bb0 fs/namei.c:1784
 [<ffffffff815a77e9>] link_path_walk+0x889/0x1200 fs/namei.c:2120
 [<ffffffff815a885d>] path_openat+0x1ad/0x3590 fs/namei.c:3533
 [<ffffffff815aff07>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff815726dd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff81572a00>] SYSC_openat fs/open.c:1099 [inline]
 [<ffffffff81572a00>] SyS_openat+0x30/0x40 fs/open.c:1093
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c