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 80000001d1f36067 PUD 1d1075067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 3797 Comm: syzkaller382090 Not tainted 4.4.115-g55a366596 #14
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d8dde000 task.stack: ffff8801d8f40000
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:ffff8801d8f47b48  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8800b0644500 RCX: ffffffff834586e6
RDX: 1ffff100160c88d0 RSI: 0000000000000002 RDI: ffff8800b0644680
RBP: ffff8801d8f47bb8 R08: 000000000000000a R09: 000000000000ffff
R10: ffffffff85700680 R11: ffffffff84418180 R12: ffff8800aba999a8
R13: ffff8801d8f47cd0 R14: ffff8800b06445e0 R15: ffff8800aba99900
FS:  00007f0cfde0e700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001c884c000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8113bd9a ffff8800b0644520 ffff8800aba99a58 ffff8801d8f47b78
 ffff8800aba99910 0000000000000000 ffff8800aba999b0 ffff8800aba99a50
 ffffffff00000000 0000000000000000 ffff8801d9943b80 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
 [<ffffffff837744df>] entry_SYSCALL_64_fastpath+0x1c/0x98
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 <ffff8801d8f47b48>
CR2: 0000000000000080
---[ end trace fcffb1edc6b67fd3 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..