BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff8345f0ce>] sock_hold include/net/sock.h:589 [inline]
IP: [<ffffffff8345f0ce>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
PGD 80000001d01c9067 PUD 1d01ca067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 3825 Comm: syzkaller490431 Not tainted 4.4.115-g55a366596 #15
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801cb1b6000 task.stack: ffff8801cc7e8000
RIP: 0010:[<ffffffff8345f0ce>]  [<ffffffff8345f0ce>] sock_hold include/net/sock.h:589 [inline]
RIP: 0010:[<ffffffff8345f0ce>]  [<ffffffff8345f0ce>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
RSP: 0018:ffff8801cc7efad0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801d141d680 RCX: ffffffff834586e6
RDX: 1ffff1003a283b00 RSI: 0000000000000002 RDI: ffff8801d141d800
RBP: ffff8801cc7efb40 R08: 000000000000000a R09: 000000000000ffff
R10: ffffffff85700680 R11: ffffffff84418180 R12: ffff8800b02d6828
R13: ffff8801cc7efc58 R14: ffff8801d141d760 R15: ffff8800b02d6780
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f7785b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001d2370000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8113bd9a ffff8801d141d6a0 ffff8800b02d68d8 ffff8801cc7efb00
 ffff8800b02d6790 0000000000000000 ffff8800b02d6830 ffff8800b02d68d0
 ffffffff00000000 0000000000000000 ffff8801cb15bb80 0000000000000000
Call Trace:
 [<ffffffff83462e5c>] pppol2tp_connect+0x10fc/0x1930 net/l2tp/l2tp_ppp.c:718
 [<ffffffff82dec456>] SYSC_connect+0x1b6/0x310 net/socket.c:1557
 [<ffffffff82deecc4>] 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
 [<ffffffff83775e6a>] 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 4b 4b 
RIP  [<ffffffff8345f0ce>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff8345f0ce>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
 RSP <ffff8801cc7efad0>
CR2: 0000000000000080
---[ end trace b41c6987e30e555d ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..