INFO: task syz-executor0:10912 blocked for more than 120 seconds.
      Not tainted 4.9.101-gd4e8148 #30
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D28504 10912  10293 0x00000004
 ffff8801d4683000 ffff88018120af40 ffff88018120af40 ffff8801d420e000
 ffff8801db221b98 ffff8801b714fce8 ffffffff839e39bd ffff8801d46838c8
 ffffed003a8d0718 ffff8801d4683000 00fffc0000000000 ffff8801db222468
Call Trace:
 [<ffffffff839e4fbf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839e5943>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff839e9dc6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839e9dc6>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff815d57ac>] __fdget_pos+0xac/0xd0 fs/file.c:781
 [<ffffffff815740be>] fdget_pos include/linux/file.h:66 [inline]
 [<ffffffff815740be>] SYSC_write fs/read_write.c:599 [inline]
 [<ffffffff815740be>] SyS_write+0x7e/0x1c0 fs/read_write.c:596
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f4893>] 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: [<ffffffff8136477c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136477c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81423c90>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3774:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f2a62>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211cd32>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor0/10912:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d57ac>] __fdget_pos+0xac/0xd0 fs/file.c:781

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.101-gd4e8148 #30
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8ab7d08 ffffffff81eb1009 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b7da0 ffff8801d8ab7d40
 ffffffff81ebc307 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb1009>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb1009>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebc307>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebc29a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b7ea4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81364d14>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81364d14>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81364d14>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81364d14>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ad9d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f4a5c>] 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: 10877 Comm: syz-executor0 Not tainted 4.9.101-gd4e8148 #30
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d420e000 task.stack: ffff880181fc8000
RIP: 0010:[<ffffffff8135cadc>] 
c [<ffffffff8135cadc>] __sanitizer_cov_trace_pc+0x4c/0x50 kernel/kcov.c:110
RSP: 0018:ffff880181fceee8  EFLAGS: 00000246
RAX: 0000000000040000 RBX: 0000000000000000 RCX: ffffc9000149f000
RDX: 0000000000040000 RSI: ffffffff81ec0c02 RDI: ffff8801cbfb8390
RBP: ffff880181fcef50 R08: ffff8801d420e988 R09: 0000000000000001
R10: ffff8801d420e000 R11: 1ffff1003a841d2c R12: ffff88018624e680
R13: 0000000000000000 R14: ffff88018624e6b0 R15: 0000000000000000
FS:  00007f89143d4700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f69f632d000 CR3: 00000001d46a2000 CR4: 00000000001606f0
DR0: 00000000200001c0 DR1: 00000000200001c0 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffffffff81ec0c02
c ffff8801cbfb8398
c ffff880181fcef80
c 0000000000000000
c
 ffffed00397f7073
c ffff8801cbfb8390
c 0000000000000041
c 0000000000000001
c
 1ffff100303f9dec
c ffff8801cbfb8390
c 0000000000000041
c 0000000000000000
c
Call Trace:
 [<ffffffff81ec0de2>] radix_tree_lookup_slot+0x72/0xc0 lib/radix-tree.c:725
 [<ffffffff81436b0e>] find_get_entry+0x8e/0x540 mm/filemap.c:1095
 [<ffffffff81437efb>] pagecache_get_page+0x4b/0x720 mm/filemap.c:1203
 [<ffffffff816215a2>] find_get_page_flags include/linux/pagemap.h:264 [inline]
 [<ffffffff816215a2>] __find_get_block_slow+0xc2/0x330 fs/buffer.c:212
 [<ffffffff81621b4e>] __find_get_block+0x23e/0x4c0 fs/buffer.c:1360
 [<ffffffff81622959>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff81622959>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff816262fd>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818c11eb>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818c11eb>] fat12_ent_bread+0x13b/0x400 fs/fat/fatent.c:75
 [<ffffffff818c367b>] fat_ent_read_block fs/fat/fatent.c:441 [inline]
 [<ffffffff818c367b>] fat_alloc_clusters+0x51b/0xe10 fs/fat/fatent.c:489
 [<ffffffff818d084f>] fat_add_cluster+0x6f/0xe0 fs/fat/inode.c:100
 [<ffffffff818d0b9f>] __fat_get_block fs/fat/inode.c:147 [inline]
 [<ffffffff818d0b9f>] fat_get_block+0x2df/0x800 fs/fat/inode.c:176
 [<ffffffff81627541>] __block_write_begin_int+0x391/0x1040 fs/buffer.c:1987
 [<ffffffff8162828f>] __block_write_begin fs/buffer.c:2038 [inline]
 [<ffffffff8162828f>] block_write_begin+0x5f/0x180 fs/buffer.c:2097
 [<ffffffff816288a3>] cont_write_begin+0x4f3/0x810 fs/buffer.c:2450
 [<ffffffff818ccd0a>] fat_write_begin+0x9a/0x120 fs/fat/inode.c:222
 [<ffffffff81433c61>] generic_perform_write+0x301/0x510 mm/filemap.c:2740
 [<ffffffff8143b63a>] __generic_file_write_iter+0x29a/0x540 mm/filemap.c:2833
 [<ffffffff8143bbc0>] generic_file_write_iter+0x2e0/0x610 mm/filemap.c:2893
 [<ffffffff8156c4f0>] new_sync_write fs/read_write.c:496 [inline]
 [<ffffffff8156c4f0>] __vfs_write+0x3e0/0x580 fs/read_write.c:509
 [<ffffffff815702e7>] vfs_write+0x187/0x530 fs/read_write.c:557
 [<ffffffff81574119>] SYSC_write fs/read_write.c:604 [inline]
 [<ffffffff81574119>] SyS_write+0xd9/0x1c0 fs/read_write.c:596
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f4893>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c<c3> 
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c