hrtimer: interrupt took 18800 ns
l2tp_core: tunl 4: sockfd_lookup(fd=6) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=6) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=6) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=6) returned -9
BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff835aa528>] sock_hold include/net/sock.h:589 [inline]
IP: [<ffffffff835aa528>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
PGD af1ed067 PUD af33f067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 5153 Comm: syz-executor0 Not tainted 4.4.151-g3a2ec58 #86
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801c8476000 task.stack: ffff8800ad2a8000
RIP: 0010:[<ffffffff835aa528>]  [<ffffffff835aa528>] sock_hold include/net/sock.h:589 [inline]
RIP: 0010:[<ffffffff835aa528>]  [<ffffffff835aa528>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
RSP: 0018:ffff8800ad2afb48  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8800b5737400 RCX: 0000000000000006
RDX: 1ffff10016ae6eb0 RSI: ffffffff835a4633 RDI: ffff8800b5737580
RBP: ffff8800ad2afbb8 R08: ffff8801c8476900 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8463a140 R12: ffff8801c80100a8
R13: ffff8800ad2afcd0 R14: ffff8801c8010000 R15: ffffffff835a3260
FS:  00007f7c2f6e3700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000000ad051000 CR4: 00000000001606f0
Stack:
 ffffffff81140a6a ffff8800b5737420 ffff8801c8010158 ffff8801c8010010
 ffffffff838cbb80 ffff8801c80100b0 ffff8801c8010150 ffff8800b57374e0
 ffffffff00000000 ffff8800ad66c400 0000000000000000 ffff8800ad66c430
Call Trace:
 [<ffffffff835ae920>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f27838>] SYSC_connect+0x1b8/0x300 net/socket.c:1570
 [<ffffffff82f2a184>] SyS_connect+0x24/0x30 net/socket.c:1551
 [<ffffffff838cc225>] 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  [<ffffffff835aa528>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff835aa528>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
 RSP <ffff8800ad2afb48>
CR2: 0000000000000080
---[ end trace 6e4556a56cf92b9b ]---