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 80000000b4a51067 PUD b3f4e067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4069 Comm: syzkaller410128 Not tainted 4.4.113-gef588ef #33
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b34097c0 task.stack: ffff8800b39e8000
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:ffff8800b39efb48  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8800b3f20c80 RCX: ffffffff83455d76
RDX: 1ffff100167e41c0 RSI: 0000000000000002 RDI: ffff8800b3f20e00
RBP: ffff8800b39efbb8 R08: 000000000000000a R09: 0000000000000000
R10: ffffffff85700640 R11: ffffffff84418100 R12: ffff8800b3f20fa8
R13: ffff8800b39efcd0 R14: ffff8800b3f20d60 R15: ffff8800b3f20f00
FS:  00007fc40534b700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000000b386a000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8113bd8a ffff8800b3f20ca0 ffff8800b3f21058 ffff8800b39efb78
 ffff8800b3f20f10 0000000000000000 ffff8800b3f20fb0 ffff8800b3f21050
 03d15af300000000 0000000000000000 ffff8800b341b300 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
 [<ffffffff83771b5f>] 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 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 <ffff8800b39efb48>
CR2: 0000000000000080
---[ end trace 4107a2e5929ec996 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..