INFO: task syz-executor0:10374 blocked for more than 140 seconds.
      Not tainted 4.9.113-g47bbcd6 #10
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D30040 10374   3863 0x00000004
 ffff88019e5d3000 ffff8801b7dd5f80 ffff8801c97f1500 ffff8801d86bc800
 ffff8801db321c18 ffff8801d6f6fce8 ffffffff839e909d ffff88019e5d38c8
 ffffed0033cba718 ffff88019e5d3000 00fffc0000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839ea69f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839eb023>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586
 [<ffffffff839ef4a6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839ef4a6>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff815d81ec>] __fdget_pos+0xac/0xd0 fs/file.c:781
 [<ffffffff8157687e>] fdget_pos include/linux/file.h:66 [inline]
 [<ffffffff8157687e>] SYSC_write fs/read_write.c:599 [inline]
 [<ffffffff8157687e>] SyS_write+0x7e/0x1c0 fs/read_write.c:596
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9f93>] 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: [<ffffffff8136675c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136675c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425de7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3774:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f8142>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211ee22>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor0/10374:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d81ec>] __fdget_pos+0xac/0xd0 fs/file.c:781
1 lock held by syz-executor0/10379:
 #0:  (&sb->s_type->i_mutex_key#21){+++++.}, at: [<ffffffff81594cb1>] inode_lock_shared include/linux/fs.h:776 [inline]
 #0:  (&sb->s_type->i_mutex_key#21){+++++.}, at: [<ffffffff81594cb1>] lookup_slow+0x141/0x470 fs/namei.c:1645
1 lock held by syz-executor0/10388:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d81ec>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by syz-executor0/10389:
 #0:  (sb_writers#15){.+.+.+}, at: [<ffffffff815e0a8f>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#15){.+.+.+}, at: [<ffffffff815e0a8f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&sb->s_type->i_mutex_key#21){+++++.}, at: [<ffffffff815a4df5>] inode_lock include/linux/fs.h:766 [inline]
 #1:  (&sb->s_type->i_mutex_key#21){+++++.}, at: [<ffffffff815a4df5>] do_last fs/namei.c:3312 [inline]
 #1:  (&sb->s_type->i_mutex_key#21){+++++.}, at: [<ffffffff815a4df5>] path_openat+0xed5/0x3590 fs/namei.c:3534
2 locks held by syz-executor0/10390:
 #0:  (sb_writers#15){.+.+.+}, at: [<ffffffff815e0a8f>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#15){.+.+.+}, at: [<ffffffff815e0a8f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&sb->s_type->i_mutex_key#21/1){+.+.+.}, at: [<ffffffff815940f6>] inode_lock_nested include/linux/fs.h:801 [inline]
 #1:  (&sb->s_type->i_mutex_key#21/1){+.+.+.}, at: [<ffffffff815940f6>] lock_rename+0x236/0x290 fs/namei.c:2857
1 lock held by syz-executor0/10391:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d81ec>] __fdget_pos+0xac/0xd0 fs/file.c:781
1 lock held by syz-executor0/10393:
 #0:  (&sb->s_type->i_mutex_key#21){+++++.}, at: [<ffffffff81594cb1>] inode_lock_shared include/linux/fs.h:776 [inline]
 #0:  (&sb->s_type->i_mutex_key#21){+++++.}, at: [<ffffffff81594cb1>] lookup_slow+0x141/0x470 fs/namei.c:1645

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d857fd08 ffffffff81eb32a9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9bd0 ffff8801d857fd40
 ffffffff81ebe5a7 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb32a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb32a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebe5a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebe53a>] 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
 [<ffffffff81366cf4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366cf4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366cf4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366cf4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa15c>] 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: 10339 Comm: syz-executor0 Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801cecb8000 task.stack: ffff88019e590000
RIP: 0010:[<ffffffff8135ea71>] 
c [<ffffffff8135ea71>] __sanitizer_cov_trace_pc+0x1/0x50 kernel/kcov.c:93
RSP: 0018:ffff88019e5970a0  EFLAGS: 00000082
RAX: 0000000000040000 RBX: ffffffff83cce7a0 RCX: ffffc90000949000
RDX: 0000000000040000 RSI: ffffffff83cce7a0 RDI: ffffffff83e2de20
RBP: ffff88019e5970e0 R08: ffff8801cecb8988 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffff10039d9712c R12: ffffffff83e2de20
R13: ffffffff83cce7a0 R14: ffff8801ba4e6150 R15: 0000000000000005
FS:  00007f3b38165700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f73c791c000 CR3: 00000001b616d000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff88019e5970e0
c ffffffff81f1acec
c ffffffff843bd658
c ffffffff83cce7a0
c
 ffff8801ba4e6150
c dffffc0000000000
c ffff8801ba4e6150
c 0000000000000005
c
 ffff88019e5970f8
c ffffffff81f1ae7c
c 0000000000000005
c ffff88019e597148
c
Call Trace:
 [<ffffffff81f1ae7c>] __this_cpu_preempt_check+0x1c/0x20 lib/smp_processor_id.c:62
 [<ffffffff816243c5>] lookup_bh_lru fs/buffer.c:1327 [inline]
 [<ffffffff816243c5>] __find_get_block+0x75/0x4c0 fs/buffer.c:1356
 [<ffffffff81625399>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff81625399>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff81628d3d>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818c4b71>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818c4b71>] fat12_ent_bread+0x231/0x400 fs/fat/fatent.c:84
 [<ffffffff818c6f0b>] fat_ent_read_block fs/fat/fatent.c:441 [inline]
 [<ffffffff818c6f0b>] fat_alloc_clusters+0x51b/0xe10 fs/fat/fatent.c:489
 [<ffffffff818d40df>] fat_add_cluster+0x6f/0xe0 fs/fat/inode.c:100
 [<ffffffff818d442f>] __fat_get_block fs/fat/inode.c:147 [inline]
 [<ffffffff818d442f>] fat_get_block+0x2df/0x800 fs/fat/inode.c:176
 [<ffffffff81629f81>] __block_write_begin_int+0x391/0x1040 fs/buffer.c:1987
 [<ffffffff8162accf>] __block_write_begin fs/buffer.c:2038 [inline]
 [<ffffffff8162accf>] block_write_begin+0x5f/0x180 fs/buffer.c:2097
 [<ffffffff8162b2e3>] cont_write_begin+0x4f3/0x810 fs/buffer.c:2450
 [<ffffffff818d059a>] fat_write_begin+0x9a/0x120 fs/fat/inode.c:222
 [<ffffffff81435dc1>] generic_perform_write+0x301/0x510 mm/filemap.c:2740
 [<ffffffff8143d79a>] __generic_file_write_iter+0x29a/0x540 mm/filemap.c:2833
 [<ffffffff8143dd20>] generic_file_write_iter+0x2e0/0x610 mm/filemap.c:2893
 [<ffffffff8156ecb0>] new_sync_write fs/read_write.c:496 [inline]
 [<ffffffff8156ecb0>] __vfs_write+0x3e0/0x580 fs/read_write.c:509
 [<ffffffff81572aa7>] vfs_write+0x187/0x530 fs/read_write.c:557
 [<ffffffff815768d9>] SYSC_write fs/read_write.c:604 [inline]
 [<ffffffff815768d9>] SyS_write+0xd9/0x1c0 fs/read_write.c:596
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9f93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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