l2tp_core: tunl 3: sockfd_lookup(fd=26) returned -9
BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff836c3c20>] sock_hold include/net/sock.h:584 [inline]
IP: [<ffffffff836c3c20>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
PGD 1bd5fe067 [  296.517522] PUD 1cc84a067 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 27658 Comm: syz-executor4 Not tainted 4.9.118-g856452b #73
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801b6780000 task.stack: ffff8801a3d10000
RIP: 0010:[<ffffffff836c3c20>]  [<ffffffff836c3c20>] sock_hold include/net/sock.h:584 [inline]
RIP: 0010:[<ffffffff836c3c20>]  [<ffffffff836c3c20>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
RSP: 0018:ffff8801a3d17ac0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801cb614a00 RCX: 1ffff10036cf011d
RDX: 1ffff100396c2920 RSI: ffff8801b67808c8 RDI: ffff8801cb614900
RBP: ffff8801a3d17b60 R08: ffff8801b67808e8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801cb6147d8
R13: 0000000000000000 R14: ffff8801cb614780 R15: 0000000000000000
FS:  00007f9fb9c92700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001ce135000 CR4: 00000000001606f0
Stack:
 ffffffff836c3e97 ffffffff836c4f31 ffff8801a43a5d48 0000000000000000
 ffff8801cb614780 ffff8801cb614b58 ffff8801cb6147d8 ffff8801cb614b50
 ffff8801cb614ab0 ffff8801cb6147a0 ffff8801a43a5500 0000000000000000
Call Trace:
 [<ffffffff836c8dd7>] pppol2tp_connect+0x10d7/0x18f0 net/l2tp/l2tp_ppp.c:718
 [<ffffffff83019958>] SYSC_connect+0x1b8/0x300 net/socket.c:1563
 [<ffffffff8301c224>] SyS_connect+0x24/0x30 net/socket.c:1544
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fca93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 00 00 49 8d be 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 7b 09 00 00 49 8b 86 80 01 00 00 <f0> ff 80 80 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 55 d0 
RIP  [<ffffffff836c3c20>] sock_hold include/net/sock.h:584 [inline]
RIP  [<ffffffff836c3c20>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
 RSP <ffff8801a3d17ac0>
CR2: 0000000000000080
---[ end trace 946fc7f941009f3c ]---