BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff835a93b8>] sock_hold include/net/sock.h:589 [inline]
IP: [<ffffffff835a93b8>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
PGD 1d8f86067 PUD 1d43f5067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 8534 Comm: syz-executor7 Not tainted 4.4.150-g5541782 #83
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800a5b8e000 task.stack: ffff8800b3370000
RIP: 0010:[<ffffffff835a93b8>]  [<ffffffff835a93b8>] sock_hold include/net/sock.h:589 [inline]
RIP: 0010:[<ffffffff835a93b8>]  [<ffffffff835a93b8>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
RSP: 0018:ffff8800b3377b48  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8800b6ff2780 RCX: ffffc900036a5000
RDX: 1ffff10016dfe520 RSI: ffffffff835a3493 RDI: ffff8800b6ff2900
RBP: ffff8800b3377bb8 R08: ffff8800a5b8e900 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8463a140 R12: ffff8801cd16cd28
R13: ffff8800b3377cd0 R14: ffff8801cd16cc80 R15: ffffffff835a20c0
FS:  00007f3637d91700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001d22ef000 CR4: 00000000001606f0
Stack:
 ffffffff8114094a ffff8800b6ff27a0 ffff8801cd16cdd8 ffff8801cd16cc90
 ffffffff838caa10 ffff8801cd16cd30 ffff8801cd16cdd0 ffff8800b6ff2860
 ffffffff00000000 ffff8800b3f70880 0000000000000000 ffff8800b3f708b0
Call Trace:
 [<ffffffff835ad7b0>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f266a8>] SYSC_connect+0x1b8/0x300 net/socket.c:1558
 [<ffffffff82f28fe4>] SyS_connect+0x24/0x30 net/socket.c:1539
 [<ffffffff838cb0a5>] entry_SYSCALL_64_fastpath+0x22/0x9e
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 f1 13 
RIP  [<ffffffff835a93b8>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff835a93b8>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
 RSP <ffff8800b3377b48>
CR2: 0000000000000080
---[ end trace 6451c90d44d54876 ]---