l2tp_core: tunl 2: sockfd_lookup(fd=5) returned -9
BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff8345c75e>] sock_hold include/net/sock.h:589 [inline]
IP: [<ffffffff8345c75e>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
PGD 80000000b5243067 PUD b478b067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 3401 Comm: syzkaller303461 Not tainted 4.4.113-ge70c132 #27
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b3c817c0 task.stack: ffff8800b4780000
RIP: 0010:[<ffffffff8345c75e>]  [<ffffffff8345c75e>] sock_hold include/net/sock.h:589 [inline]
RIP: 0010:[<ffffffff8345c75e>]  [<ffffffff8345c75e>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
RSP: 0018:ffff8800b4787ad0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8800b4534a00 RCX: ffffffff83455d76
RDX: 1ffff100168a6970 RSI: 0000000000000002 RDI: ffff8800b4534b80
RBP: ffff8800b4787b40 R08: ffff8800b4534810 R09: 0000000000000000
R10: ffffffff85700640 R11: ffffffff84418100 R12: ffff8800b4534828
R13: ffff8800b4787c58 R14: ffff8800b4534ae0 R15: ffff8800b4534780
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:00000000f7733b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000000b7f50000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8113bd8a ffff8800b4534a20 ffff8800b45348d8 ffff8800b4787b00
 ffff8800b4534790 0000000000000000 ffff8800b4534830 ffff8800b45348d0
 5e0525fd00000000 0000000000000000 ffff8800b467ee80 0000000000000000
Call Trace:
 [<ffffffff834604ec>] pppol2tp_connect+0x10fc/0x1930 net/l2tp/l2tp_ppp.c:718
 [<ffffffff82deabd6>] SYSC_connect+0x1b6/0x310 net/socket.c:1557
 [<ffffffff82ded444>] SyS_connect+0x24/0x30 net/socket.c:1538
 [<ffffffff81006d74>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
 [<ffffffff81006d74>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
 [<ffffffff837734ea>] sysenter_flags_fixed+0xd/0x17
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 1b 4b 
RIP  [<ffffffff8345c75e>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff8345c75e>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
 RSP <ffff8800b4787ad0>
CR2: 0000000000000080
---[ end trace db8a13e85f713859 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
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Kernel Offset: disabled
Rebooting in 86400 seconds..