l2tp_core: tunl 4: sockfd_lookup(fd=6) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=6) returned -9
hrtimer: interrupt took 27891 ns
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: [<ffffffff835aa438>] sock_hold include/net/sock.h:589 [inline]
IP: [<ffffffff835aa438>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
PGD b6a73067 PUD b7b43067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4586 Comm: syz-executor0 Not tainted 4.4.151-ge917467 #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d4134800 task.stack: ffff8800b6a30000
RIP: 0010:[<ffffffff835aa438>]  [<ffffffff835aa438>] sock_hold include/net/sock.h:589 [inline]
RIP: 0010:[<ffffffff835aa438>]  [<ffffffff835aa438>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
RSP: 0018:ffff8800b6a37ad0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801d3b1e280 RCX: 0000000000000006
RDX: 1ffff1003a763c80 RSI: ffffffff835a4543 RDI: ffff8801d3b1e400
RBP: ffff8800b6a37b40 R08: ffff8801d4135100 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8463a140 R12: ffff8801d3a18328
R13: ffff8800b6a37c58 R14: ffff8801d3a18280 R15: ffffffff835a3170
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:00000000f77d6b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000000b6ad6000 CR4: 00000000001606f0
Stack:
 ffffffff81140a6a ffff8801d3b1e2a0 ffff8801d3a183d8 ffff8801d3a18290
 ffffffff838cba90 ffff8801d3a18330 ffff8801d3a183d0 ffff8801d3b1e360
 ffffffff00000000 ffff8800b6eadd80 0000000000000000 ffff8800b6eaddb0
Call Trace:
 [<ffffffff835ae830>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f27758>] SYSC_connect+0x1b8/0x300 net/socket.c:1558
 [<ffffffff82f2a094>] SyS_connect+0x24/0x30 net/socket.c:1539
 [<ffffffff81006d94>] do_syscall_32_irqs_on arch/x86/entry/common.c:393 [inline]
 [<ffffffff81006d94>] do_fast_syscall_32+0x324/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838cda83>] sysenter_flags_fixed+0xd/0x1a
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  [<ffffffff835aa438>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff835aa438>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
 RSP <ffff8800b6a37ad0>
CR2: 0000000000000080
---[ end trace 6dd89698b77aebdd ]---