l2tp_core: tunl 3: sockfd_lookup(fd=0) returned -9
BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff8346107e>] sock_hold include/net/sock.h:589 [inline]
IP: [<ffffffff8346107e>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
PGD 80000000b690e067 PUD b5f56067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 7498 Comm: syz-executor1 Not tainted 4.4.112-g5f6325b #28
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b75517c0 task.stack: ffff8801d4740000
RIP: 0010:[<ffffffff8346107e>]  [<ffffffff8346107e>] sock_hold include/net/sock.h:589 [inline]
RIP: 0010:[<ffffffff8346107e>]  [<ffffffff8346107e>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
RSP: 0018:ffff8801d4747b48  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801d5091680 RCX: ffffffff8345a696
RDX: 1ffff1003aa12300 RSI: 0000000000000002 RDI: ffff8801d5091800
RBP: ffff8801d4747bb8 R08: ffff8801d5091490 R09: 0000000000000000
R10: ffffffff856fe600 R11: ffffffff84417140 R12: ffff8801d50914a8
R13: ffff8801d4747cd0 R14: ffff8801d5091760 R15: ffff8801d5091400
FS:  00007fdbb6858700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000000b4e90000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8113bd0a ffff8801d50916a0 ffff8801d5091558 ffff8801d4747b78
 ffff8801d5091410 0000000000000000 ffff8801d50914b0 ffff8801d5091550
 9a066c8500000000 0000000000000000 ffff8801d7732a80 0000000000000000
Call Trace:
 [<ffffffff83464e0c>] pppol2tp_connect+0x10fc/0x1930 net/l2tp/l2tp_ppp.c:718
 [<ffffffff82deefe6>] SYSC_connect+0x1b6/0x310 net/socket.c:1557
 [<ffffffff82df1854>] SyS_connect+0x24/0x30 net/socket.c:1538
 [<ffffffff83776499>] entry_SYSCALL_64_fastpath+0x16/0x92
Code: 00 00 48 8d bb 80 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 4f 07 00 00 48 8b 83 80 01 00 00 <f0> ff 80 80 00 00 00 48 8d 43 20 48 89 c7 48 89 45 b8 e8 3b 4b 
RIP  [<ffffffff8346107e>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff8346107e>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
 RSP <ffff8801d4747b48>
CR2: 0000000000000080
---[ end trace bcefddef13b484fd ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
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Kernel Offset: disabled
Rebooting in 86400 seconds..