ip (4000) used greatest stack depth: 23200 bytes left
IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
l2tp_core: tunl 4: sockfd_lookup(fd=5) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=5) returned -9
BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff835a8968>] sock_hold include/net/sock.h:589 [inline]
IP: [<ffffffff835a8968>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
PGD 1d8373067 PUD 1da0b8067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 6478 Comm: syz-executor0 Not tainted 4.4.149-gf76bdbd #82
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800ac4b8000 task.stack: ffff8801d7440000
RIP: 0010:[<ffffffff835a8968>]  [<ffffffff835a8968>] sock_hold include/net/sock.h:589 [inline]
RIP: 0010:[<ffffffff835a8968>]  [<ffffffff835a8968>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
RSP: 0018:ffff8801d7447b48  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8800b9405180 RCX: 0000000000000006
RDX: 1ffff10017280a60 RSI: ffffffff835a2a43 RDI: ffff8800b9405300
RBP: ffff8801d7447bb8 R08: ffff8800ac4b8900 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8463a140 R12: ffff8800b36739a8
R13: ffff8801d7447cd0 R14: ffff8800b3673900 R15: ffffffff835a1670
FS:  00007fc8fe06b700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001cca7e000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8114050a ffff8800b94051a0 ffff8800b3673a58 ffff8800b3673910
 ffffffff838c9fc0 ffff8800b36739b0 ffff8800b3673a50 ffff8800b9405260
 ffffffff00000000 ffff8800acbd4400 0000000000000000 ffff8800acbd4430
Call Trace:
 [<ffffffff835acd60>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f25c58>] SYSC_connect+0x1b8/0x300 net/socket.c:1558
 [<ffffffff82f28594>] SyS_connect+0x24/0x30 net/socket.c:1539
 [<ffffffff838ca665>] 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  [<ffffffff835a8968>] sock_hold include/net/sock.h:589 [inline]
RIP  [<ffffffff835a8968>] l2tp_session_create+0x948/0x1030 net/l2tp/l2tp_core.c:1809
 RSP <ffff8801d7447b48>
CR2: 0000000000000080
---[ end trace a17a092edc082941 ]---