BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff8345f0de>] sock_hold include/net/sock.h:589 [inline]
IP: [<ffffffff8345f0de>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
PGD 80000001ce3c2067 PUD 1ce3ae067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 6830 Comm: syzkaller186994 Not tainted 4.4.115-g0e9bcc1 #12
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b5f46000 task.stack: ffff8801d38c0000
RIP: 0010:[<ffffffff8345f0de>]  [<ffffffff8345f0de>] sock_hold include/net/sock.h:589 [inline]
RIP: 0010:[<ffffffff8345f0de>]  [<ffffffff8345f0de>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
RSP: 0018:ffff8801d38c7ad0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801cd182280 RCX: ffffffff834586f6
RDX: 1ffff10039a30480 RSI: 0000000000000002 RDI: ffff8801cd182400
RBP: ffff8801d38c7b40 R08: 000000000000000a R09: 000000000000ffff
R10: ffffffff85700680 R11: ffffffff84418180 R12: ffff8800b6266aa8
R13: ffff8801d38c7c58 R14: ffff8801cd182360 R15: ffff8800b6266a00
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:00000000f77a2b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001d0718000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8113bd9a ffff8801cd1822a0 ffff8800b6266b58 ffff8801d38c7b00
 ffff8800b6266a10 0000000000000000 ffff8800b6266ab0 ffff8800b6266b50
 ffffffff00000000 0000000000000000 ffff8800b5e11980 0000000000000000
Call Trace:
 [<ffffffff83462e6c>] pppol2tp_connect+0x10fc/0x1930 net/l2tp/l2tp_ppp.c:718
 [<ffffffff82dec476>] SYSC_connect+0x1b6/0x310 net/socket.c:1557
 [<ffffffff82deece4>] 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
 [<ffffffff83775eaa>] 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  [<ffffffff8345f0de>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff8345f0de>] l2tp_session_create+0x93e/0x10f0 net/l2tp/l2tp_core.c:1805
 RSP <ffff8801d38c7ad0>
CR2: 0000000000000080
---[ end trace 7b966029b5b20255 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..