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 80000001d0a86067 PUD 1d0a85067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 3336 Comm: syzkaller603077 Not tainted 4.4.112-g3fc4284 #32
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b4bd4740 task.stack: ffff8801d0148000
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:ffff8801d014fb48  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8800b33cf680 RCX: ffffffff8345a3e6
RDX: 1ffff10016679f00 RSI: 0000000000000002 RDI: ffff8800b33cf800
RBP: ffff8801d014fbb8 R08: ffff8800b33cfc10 R09: 0000000000000000
R10: ffffffff856fe600 R11: ffffffff84417100 R12: ffff8800b33cfc28
R13: ffff8801d014fcd0 R14: ffff8800b33cf760 R15: ffff8800b33cfb80
FS:  00007ffb55aef700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001d002a000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8113bd0a ffff8800b33cf6a0 ffff8800b33cfcd8 ffff8801d014fb78
 ffff8800b33cfb90 0000000000000000 ffff8800b33cfc30 ffff8800b33cfcd0
 ffffffff00000000 0000000000000000 ffff8800b3bedd80 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
 [<ffffffff837761d9>] 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  [<ffffffff83460dce>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff83460dce>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
 RSP <ffff8801d014fb48>
CR2: 0000000000000080
---[ end trace 07d9d8ef3b8416ab ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..