TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
INFO: task syz-executor4:21075 blocked for more than 120 seconds.
      Not tainted 4.4.132-g4b08356 #48
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor4   D ffff8800975cfac0 28992 21075   3923 0x20020004
 ffff8800975cfac0 ffffffff84206e48 ffff8801d6cdb8f8 ffffffff853e1be0
 ffff8801d6cdb800 ffff8801db31fdb8 ffff8801db31fde0 ffff8801db31f4d8
 ffff8801db31f4c0 ffff8801bd5ae000 ffff8801d6cdb000 0000000000000000
Call Trace:
 [<ffffffff838b226a>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff838bd681>] schedule_timeout+0x481/0x8b0 kernel/time/timer.c:1515
 [<ffffffff838b53ae>] do_wait_for_common kernel/sched/completion.c:75 [inline]
 [<ffffffff838b53ae>] __wait_for_common kernel/sched/completion.c:93 [inline]
 [<ffffffff838b53ae>] wait_for_common kernel/sched/completion.c:101 [inline]
 [<ffffffff838b53ae>] wait_for_completion+0x1fe/0x2e0 kernel/sched/completion.c:122
 [<ffffffff81d5abd9>] submit_bio_wait+0xf9/0x150 block/bio.c:887
 [<ffffffff81d8d204>] blkdev_issue_flush+0x124/0x1e0 block/blk-flush.c:488
 [<ffffffff815cff45>] blkdev_fsync+0x85/0xb0 fs/block_dev.c:364
 [<ffffffff815bcbbc>] vfs_fsync_range+0x10c/0x260 fs/sync.c:195
 [<ffffffff815bcd82>] vfs_fsync fs/sync.c:209 [inline]
 [<ffffffff815bcd82>] do_fsync+0x42/0xb0 fs/sync.c:219
 [<ffffffff815bd529>] SYSC_fdatasync fs/sync.c:233 [inline]
 [<ffffffff815bd529>] SyS_fdatasync+0x19/0x20 fs/sync.c:231
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c1bea>] sysenter_flags_fixed+0xd/0x17
no locks held by syz-executor4/21075.
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.132-g4b08356 #48
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84417840 task.stack: ffffffff84400000
RIP: 0010:[<ffffffff812afd2c>]  [<ffffffff812afd2c>] ktime_get+0x1c/0x1e0 kernel/time/timekeeping.c:751
RSP: 0018:ffffffff84407d98  EFLAGS: 00000093
RAX: 0000000000000000 RBX: ffff8801db219c40 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff812afd26 RDI: ffffffff844180e4
RBP: ffffffff84407df0 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: ffffffff84417840 R12: ffff8801db219cb4
R13: ffff8801db219cd0 R14: fffffbfff074890c R15: ffffffff84a05ba8
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f132c1ca000 CR3: 00000001d3eda000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff00000001 ffffffff84407de0 ffffffff81e6db7b 0000000000000002
 0000000000019c40 0000000000000046 ffff8801db219c40 ffff8801db219cb4
 ffff8801db219cd0 fffffbfff074890c ffffffff84a05ba8 ffffffff84407e28
Call Trace:
 [<ffffffff812c6fe3>] tick_nohz_idle_exit+0x153/0x3d0 kernel/time/tick-sched.c:940
 [<ffffffff8121bd87>] cpu_idle_loop kernel/sched/idle.c:267 [inline]
 [<ffffffff8121bd87>] cpu_startup_entry+0x2a7/0x780 kernel/sched/idle.c:301
 [<ffffffff838ad3d1>] rest_init+0x188/0x18e init/main.c:410
 [<ffffffff84a4b8a1>] start_kernel+0x6b3/0x6e7 init/main.c:682
 [<ffffffff84a4a30f>] x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:196
 [<ffffffff84a4a450>] x86_64_start_kernel+0x13f/0x162 arch/x86/kernel/head64.c:185
Code: 7b 93 24 00 eb 8f 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 53 48 83 ec 30 e8 ca 14 0a 00 8b 05 e8 52 76 03 <85> c0 0f 85 8b 01 00 00 49 c7 c4 80 16 93 85 49 bd 00 00 00 00 
NMI backtrace for cpu 1
CPU: 1 PID: 492 Comm: khungtaskd Not tainted 4.4.132-g4b08356 #48
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bac60000 task.stack: ffff8800bb348000
RIP: 0010:[<ffffffff810bfe16>]  [<ffffffff810bfe16>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810bfe16>]  [<ffffffff810bfe16>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810bfe16>]  [<ffffffff810bfe16>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810bfe16>]  [<ffffffff810bfe16>] flat_send_IPI_mask+0xf6/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bb34fcc8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8800bb34fcf0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: 0000000000000002 R15: ffffffff8446f7a0
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f417dab1000 CR3: 00000001d3eda000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8446f7a0 ffffffff84a18ae0 0000000000000007 fffffbfff0942c0c
 0000000000000040 ffff8800bb34fd10 ffffffff810b5dd1 ffffffff83c0b220
 0000000000000003 ffff8800bb34fd68 ffffffff81e19063 ffff8801d6cdb000
Call Trace:
 [<ffffffff810b5dd1>] nmi_raise_cpu_backtrace+0x61/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81e19063>] nmi_trigger_all_cpu_backtrace.cold.4+0x70/0xad lib/nmi_backtrace.c:85
 [<ffffffff810b5e74>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff8141a0c9>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff8141a0c9>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8141a0c9>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8141a0c9>] watchdog.cold.1+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff81190768>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff838c06d5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
Code: b3 5f ff f6 c4 10 75 e2 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 f2 09 da 80 cf 04 41 83 fe 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 75 1a 4c 89 e7 57 9d 0f 1f 44 00 00 e8 f2