TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
INFO: task syz-executor0:10178 blocked for more than 120 seconds.
      Not tainted 4.9.101-gaef17a5 #32
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D29560 10178   3786 0x00000004
 ffff8801ce266000 0000000000000000 ffff8801d6fb4a80 ffff8801d06ab000
 ffff8801db221b98 ffff8801d56efa50 ffffffff839e39bd 0000000000000002
 0000000041b58ab3 ffffffff843b8b43 00ffffff8121f220 ffff8801db222468
Call Trace:
 [<ffffffff839e4fbf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff81280e99>] exp_funnel_lock kernel/rcu/tree_exp.h:279 [inline]
 [<ffffffff81280e99>] _synchronize_rcu_expedited+0x689/0x840 kernel/rcu/tree_exp.h:569
 [<ffffffff81283be2>] synchronize_rcu_expedited+0x22/0x30 kernel/rcu/tree_exp.h:687
 [<ffffffff83069d7f>] synchronize_net+0x2f/0x50 net/core/dev.c:7834
 [<ffffffff83686750>] packet_release+0x680/0x9d0 net/packet/af_packet.c:3041
 [<ffffffff8300fab6>] sock_release+0x96/0x1c0 net/socket.c:599
 [<ffffffff83015db1>] SYSC_socketpair net/socket.c:1369 [inline]
 [<ffffffff83015db1>] SyS_socketpair+0x3d1/0x510 net/socket.c:1273
 [<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
1 lock held by rsyslogd/3597:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d57ac>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3693:
 #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

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.101-gaef17a5 #32
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8427d08 ffffffff81eb1009 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b7da0 ffff8801d8427d40
 ffffffff81ebc307 0000000000000000 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 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff839f34c6