netlink: 20 bytes leftover after parsing attributes in process `syz-executor3'.
BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff835a6d48>] sock_hold include/net/sock.h:589 [inline]
IP: [<ffffffff835a6d48>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
PGD b3eb1067 PUD b7505067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 9007 Comm: syz-executor5 Not tainted 4.4.146-g1396226 #15
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b9001800 task.stack: ffff8801be8d8000
RIP: 0010:[<ffffffff835a6d48>]  [<ffffffff835a6d48>] sock_hold include/net/sock.h:589 [inline]
RIP: 0010:[<ffffffff835a6d48>]  [<ffffffff835a6d48>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
RSP: 0018:ffff8801be8dfad0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8800b0231680 RCX: ffffc90004abb000
RDX: 1ffff10016046300 RSI: ffffffff835a0e23 RDI: ffff8800b0231800
RBP: ffff8801be8dfb40 R08: ffff8800b9002100 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8463a1e0 R12: ffff8800b92e9c28
R13: ffff8801be8dfc58 R14: ffff8800b92e9b80 R15: ffffffff835a0900
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:00000000f57d5b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000000bab99000 CR4: 00000000001606f0
Stack:
 ffffffff8113fc41 ffff8800b02316a0 ffff8800b92e9cd8 ffff8800b92e9b90
 ffffffff838c83a0 ffff8800b92e9c30 ffff8800b92e9cd0 ffff8800b0231760
 f8b3772000000000 ffff8801cc5d1100 0000000000000000 ffff8801cc5d1130
Call Trace:
 [<ffffffff835ab140>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f240b8>] SYSC_connect+0x1b8/0x300 net/socket.c:1558
 [<ffffffff82f269f4>] 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
 [<ffffffff838ca383>] 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  [<ffffffff835a6d48>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff835a6d48>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
 RSP <ffff8801be8dfad0>
CR2: 0000000000000080
---[ end trace 1917d542b5126342 ]---