syz-executor4 (8653) used greatest stack depth: 23688 bytes left
INFO: task syz-executor3:8738 blocked for more than 140 seconds.
      Not tainted 4.9.118-g47b77b8 #20
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor3   D29816  8738   3889 0x00000004
 ffff88019e571800 ffff8801d92764c0 ffff8801d9b18000 ffff8801d84c9800
 ffff8801db321c18 ffff88019d6cfcc8 ffffffff839ebbad ffff88019e5720c8
 ffffed0033cae418 ffff88019e571800 00fffc0000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839ed1af>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839edb33>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586
 [<ffffffff839f1fb6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839f1fb6>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff815d853c>] __fdget_pos+0xac/0xd0 fs/file.c:781
 [<ffffffff815b52b5>] fdget_pos include/linux/file.h:66 [inline]
 [<ffffffff815b52b5>] SYSC_getdents fs/readdir.c:226 [inline]
 [<ffffffff815b52b5>] SyS_getdents+0x115/0x2a0 fs/readdir.c:211
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fca93>] 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: [<ffffffff8136679c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136679c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425fb7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3675:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d853c>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3773:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839fac52>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff821207a2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor3/8664:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d853c>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #1:  (&sb->s_type->i_mutex_key#22){++++.+}, at: [<ffffffff815b41b3>] inode_lock_shared include/linux/fs.h:776 [inline]
 #1:  (&sb->s_type->i_mutex_key#22){++++.+}, at: [<ffffffff815b41b3>] iterate_dir+0xc3/0x600 fs/readdir.c:39
1 lock held by syz-executor3/8738:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d853c>] __fdget_pos+0xac/0xd0 fs/file.c:781
1 lock held by syz-executor3/8740:
 #0:  (&sb->s_type->i_mutex_key#22){++++.+}, at: [<ffffffff815e1bfc>] inode_lock include/linux/fs.h:766 [inline]
 #0:  (&sb->s_type->i_mutex_key#22){++++.+}, at: [<ffffffff815e1bfc>] lock_mount+0x8c/0x2c0 fs/namespace.c:2077

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.118-g47b77b8 #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d85ffd08 ffffffff81eb4b89 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9bd0 ffff8801d85ffd40
 ffffffff81ebfe87 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb4b89>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4b89>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebfe87>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebfe1a>] 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
 [<ffffffff81366d34>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366d34>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366d34>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366d34>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fcc5c>] 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 skipped: idling at pc 0xffffffff839fb6b6