TCP: request_sock_TCPv6: Possible SYN flooding on port 20018. Sending cookies.  Check SNMP counters.
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 16856 Comm: syz-executor7 Not tainted 4.9.81-gf8bbe51 #32
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801c41f6000 task.stack: ffff8801baa08000
RIP: 0010:[<ffffffff833c8308>]  [<ffffffff833c8308>] xfrm_policy_ok net/xfrm/xfrm_policy.c:2403 [inline]
RIP: 0010:[<ffffffff833c8308>]  [<ffffffff833c8308>] __xfrm_policy_check+0xbf8/0x1a30 net/xfrm/xfrm_policy.c:2579
RSP: 0018:ffff8801db2075a0  EFLAGS: 00010202
RAX: 0000000000000006 RBX: 0000000000000000 RCX: ffffffff833c82d7
RDX: 0000000000000002 RSI: ffff8801db2076e8 RDI: 0000000000000032
RBP: ffff8801db2077e8 R08: 0000000000000003 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
R13: dffffc0000000000 R14: dffffc0000000000 R15: 0000000000000000
FS:  00007fbfe3c8c700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbfe3c8bdb8 CR3: 00000001b7032000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff833c784d ffff8801db2076d8 ffff8801db207640 00000001c41f68a8
 ffff8801db207680 ffff8801c0eb3e28 ffff8801db207650 ffff8801d6240000
 0000000200026000 1ffff1003b640ec4 ffff8801db2076e8 ffff8801db207740
Call Trace:
 [<ffffffff832c4047>] __xfrm_policy_check2 include/net/xfrm.h:1063 [inline]
 [<ffffffff832c4047>] xfrm_policy_check include/net/xfrm.h:1072 [inline]
 [<ffffffff832c4047>] xfrm4_policy_check include/net/xfrm.h:1077 [inline]
 [<ffffffff832c4047>] udp_queue_rcv_skb+0x537/0x1760 net/ipv4/udp.c:1509
 [<ffffffff832c58b7>] __udp4_lib_rcv+0x647/0x2b70 net/ipv4/udp.c:1772
 [<ffffffff832c8de1>] udp_rcv+0x21/0x30 net/ipv4/udp.c:1964
 [<ffffffff831edf45>] ip_local_deliver_finish+0x285/0xa80 net/ipv4/ip_input.c:216
 [<ffffffff831eef8a>] NF_HOOK_THRESH include/linux/netfilter.h:232 [inline]
 [<ffffffff831eef8a>] NF_HOOK include/linux/netfilter.h:255 [inline]
 [<ffffffff831eef8a>] ip_local_deliver+0x30a/0x4d0 net/ipv4/ip_input.c:257
 [<ffffffff831ecadb>] dst_input include/net/dst.h:513 [inline]
 [<ffffffff831ecadb>] ip_rcv_finish+0x71b/0x1900 net/ipv4/ip_input.c:396
 [<ffffffff831efd12>] NF_HOOK_THRESH include/linux/netfilter.h:232 [inline]
 [<ffffffff831efd12>] NF_HOOK include/linux/netfilter.h:255 [inline]
 [<ffffffff831efd12>] ip_rcv+0xbc2/0x1620 net/ipv4/ip_input.c:487
 [<ffffffff82f3c643>] __netif_receive_skb_core+0xa33/0x29e0 net/core/dev.c:4252
 [<ffffffff82f3e64b>] __netif_receive_skb+0x5b/0x1c0 net/core/dev.c:4290
 [<ffffffff82f3e984>] process_backlog+0x1d4/0x690 net/core/dev.c:4911
 [<ffffffff82f44a96>] napi_poll net/core/dev.c:5212 [inline]
 [<ffffffff82f44a96>] net_rx_action+0x396/0xe00 net/core/dev.c:5277
 [<ffffffff838ba846>] __do_softirq+0x206/0x951 kernel/softirq.c:284
 [<ffffffff838b4d9c>] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:831
 <EOI> [   83.943772]  [<ffffffff81145219>] do_softirq.part.16+0x99/0xb0 kernel/softirq.c:328
 [<ffffffff81146a09>] do_softirq+0x19/0x20 kernel/softirq.c:331
 [<ffffffff82f41f90>] netif_rx_ni+0x140/0x320 net/core/dev.c:3882
 [<ffffffff82715366>] tun_get_user+0xac6/0x2110 drivers/net/tun.c:1330
 [<ffffffff82716bc5>] tun_chr_write_iter+0xd5/0x190 drivers/net/tun.c:1353
 [<ffffffff8156e3e5>] do_iter_readv_writev+0x2b5/0x400 fs/read_write.c:695
 [<ffffffff815709d3>] do_readv_writev+0x313/0x750 fs/read_write.c:872
 [<ffffffff81571347>] vfs_writev+0x87/0xc0 fs/read_write.c:911
 [<ffffffff81571466>] do_writev+0xe6/0x250 fs/read_write.c:944
 [<ffffffff815744d7>] SYSC_writev fs/read_write.c:1017 [inline]
 [<ffffffff815744d7>] SyS_writev+0x27/0x30 fs/read_write.c:1014
 [<ffffffff81006505>] do_syscall_64+0x1a5/0x490 arch/x86/entry/common.c:282
 [<ffffffff838b3dbd>] entry_SYSCALL_64_after_swapgs+0x47/0xc5
Code: ff 48 c1 e8 03 42 80 3c 30 00 0f 85 f9 0b 00 00 48 8b 85 08 fe ff ff 48 8b 18 48 8d 7b 32 48 89 f8 48 89 fa 48 c1 e8 03 83 e2 07 <42> 0f b6 04 30 38 d0 7f 08 84 c0 0f 85 c3 0b 00 00 0f b6 43 32 
RIP  [<ffffffff833c8308>] xfrm_policy_ok net/xfrm/xfrm_policy.c:2403 [inline]
RIP  [<ffffffff833c8308>] __xfrm_policy_check+0xbf8/0x1a30 net/xfrm/xfrm_policy.c:2579
 RSP <ffff8801db2075a0>
---[ end trace db65040908313b9b ]---