BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff83460dce>] sock_hold include/net/sock.h:589 [inline]
IP: [<ffffffff83460dce>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
PGD 80000000b65bd067 PUD b6422067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 6910 Comm: syzkaller912044 Not tainted 4.4.112-g3fc4284 #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801ce3197c0 task.stack: ffff8801ce7b8000
RIP: 0010:[<ffffffff83460dce>]  [<ffffffff83460dce>] sock_hold include/net/sock.h:589 [inline]
RIP: 0010:[<ffffffff83460dce>]  [<ffffffff83460dce>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
RSP: 0018:ffff8801ce7bfad0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801cf6d9400 RCX: ffffffff8345a3e6
RDX: 1ffff10039edb2b0 RSI: 0000000000000002 RDI: ffff8801cf6d9580
RBP: ffff8801ce7bfb40 R08: 000000000000000a R09: 0000000000000000
R10: ffffffff856fe600 R11: ffffffff84417100 R12: ffff8801cf6d85a8
R13: ffff8801ce7bfc58 R14: ffff8801cf6d94e0 R15: ffff8801cf6d8500
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f774bb40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000000b2e4a000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8113bd0a ffff8801cf6d9420 ffff8801cf6d8658 ffff8801ce7bfb00
 ffff8801cf6d8510 0000000000000000 ffff8801cf6d85b0 ffff8801cf6d8650
 ffffffff00000000 0000000000000000 ffff8800b2a58000 0000000000000000
Call Trace:
 [<ffffffff83464b5c>] pppol2tp_connect+0x10fc/0x1930 net/l2tp/l2tp_ppp.c:718
 [<ffffffff82deed36>] SYSC_connect+0x1b6/0x310 net/socket.c:1557
 [<ffffffff82df15a4>] SyS_connect+0x24/0x30 net/socket.c:1538
 [<ffffffff81006d84>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
 [<ffffffff81006d84>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
 [<ffffffff83777b6a>] 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 3b 4b 
RIP  [<ffffffff83460dce>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff83460dce>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
 RSP <ffff8801ce7bfad0>
CR2: 0000000000000080
---[ end trace 289d7931c84adbbe ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..