BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff835a1078>] sock_hold include/net/sock.h:589 [inline]
IP: [<ffffffff835a1078>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
PGD 1d46d1067 PUD 1d676f067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 26871 Comm: syz-executor6 Not tainted 4.4.141-g9664bde #11
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800a425e000 task.stack: ffff8801cd5d8000
RIP: 0010:[<ffffffff835a1078>]  [<ffffffff835a1078>] sock_hold include/net/sock.h:589 [inline]
RIP: 0010:[<ffffffff835a1078>]  [<ffffffff835a1078>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
RSP: 0018:ffff8801cd5dfad0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8800b1910280 RCX: ffffc900058c2000
RDX: 1ffff10016322080 RSI: ffffffff8359b153 RDI: ffff8800b1910400
RBP: ffff8801cd5dfb40 R08: ffff8800a425e900 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff84638de0 R12: ffff8801d052ad28
R13: ffff8801cd5dfc58 R14: ffff8801d052ac80 R15: ffffffff83599d80
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f578cb40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001d3c63000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8113da8a ffff8800b19102a0 ffff8801d052add8 ffff8801d052ac90
 ffffffff838c2670 ffff8801d052ad30 ffff8801d052add0 ffff8800b1910360
 ffffffff00000000 ffff8800a35b4c80 0000000000000000 ffff8800a35b4cb0
Call Trace:
 [<ffffffff835a5470>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f1ec78>] SYSC_connect+0x1b8/0x300 net/socket.c:1557
 [<ffffffff82f215b4>] SyS_connect+0x24/0x30 net/socket.c:1538
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:393 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838c466a>] 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 36 06 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 b0 e8 91 13 
RIP  [<ffffffff835a1078>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff835a1078>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
 RSP <ffff8801cd5dfad0>
CR2: 0000000000000080
---[ end trace c0133b04eaabe90e ]---