TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
9pnet: p9_errstr2errno: server reported unknown error le0/flô|›j
INFO: task syz-executor2:9445 blocked for more than 140 seconds.
      Not tainted 4.9.122-g54068d6 #26
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor2   D29144  9445   3868 0x00000004
 ffff8801cc7bb000 0000000000000000 ffff8801d55ab9c0 ffff8801d9a6b000
 ffff8801db321c18 ffff8801ca31fa78 ffffffff839efdcd ffffffff812378c7
 0000000000000000 ffff8801cc7bb8c0 0000000600000007 ffff8801db3224e8
Call Trace:
 [<ffffffff839f13cf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839fca08>] __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:526 [inline]
 [<ffffffff839fca08>] rwsem_down_write_failed+0x598/0x990 kernel/locking/rwsem-xadd.c:555
 [<ffffffff81eecb47>] call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105
 [<ffffffff839fa7dc>] __down_write arch/x86/include/asm/rwsem.h:125 [inline]
 [<ffffffff839fa7dc>] down_write+0x5c/0xa0 kernel/locking/rwsem.c:54
 [<ffffffff8156ceab>] inode_lock include/linux/fs.h:766 [inline]
 [<ffffffff8156ceab>] chown_common+0x2bb/0x550 fs/open.c:626
 [<ffffffff81570afb>] SYSC_fchownat fs/open.c:659 [inline]
 [<ffffffff81570afb>] SyS_fchownat fs/open.c:639 [inline]
 [<ffffffff81570afb>] SYSC_chown fs/open.c:673 [inline]
 [<ffffffff81570afb>] SyS_chown+0xdb/0x160 fs/open.c:671
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a00cd3>] 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: [<ffffffff81368a5c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81368a5c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff814282c8>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by rs:main Q:Reg/3675:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815dbb4c>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff815767be>] file_start_write include/linux/fs.h:2640 [inline]
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff815767be>] vfs_write+0x3ae/0x530 fs/read_write.c:556
2 locks held by getty/3773:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839fee72>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82124562>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor2/9435:
 #0:  (sb_writers#18){.+.+.+}, at: [<ffffffff815e442f>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#18){.+.+.+}, at: [<ffffffff815e442f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&sb->s_type->i_mutex_key#26){++++.+}, at: [<ffffffff8156ceab>] inode_lock include/linux/fs.h:766 [inline]
 #1:  (&sb->s_type->i_mutex_key#26){++++.+}, at: [<ffffffff8156ceab>] chown_common+0x2bb/0x550 fs/open.c:626
2 locks held by syz-executor2/9445:
 #0:  (sb_writers#18){.+.+.+}, at: [<ffffffff815e442f>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#18){.+.+.+}, at: [<ffffffff815e442f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&sb->s_type->i_mutex_key#26){++++.+}, at: [<ffffffff8156ceab>] inode_lock include/linux/fs.h:766 [inline]
 #1:  (&sb->s_type->i_mutex_key#26){++++.+}, at: [<ffffffff8156ceab>] chown_common+0x2bb/0x550 fs/open.c:626

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.122-g54068d6 #26
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8bd7d08 ffffffff81eb8829 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9fa0 ffff8801d8bd7d40
 ffffffff81ec3b67 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb8829>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb8829>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ec3b67>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ec3afa>] 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
 [<ffffffff81368ff4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81368ff4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81368ff4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81368ff4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119f38d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff83a00e9c>] 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 skipped: idling at pc 0xffffffff839ff8d6