BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff836c3e40>] sock_hold include/net/sock.h:584 [inline]
IP: [<ffffffff836c3e40>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
PGD 1ccbf5067 [  212.454947] PUD 1be707067 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 15723 Comm: syz-executor2 Not tainted 4.9.119-g9dc978d #75
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801b950e000 task.stack: ffff8801b9748000
RIP: 0010:[<ffffffff836c3e40>]  [<ffffffff836c3e40>] sock_hold include/net/sock.h:584 [inline]
RIP: 0010:[<ffffffff836c3e40>]  [<ffffffff836c3e40>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
RSP: 0018:ffff8801b974fac0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801d4913900 RCX: 1ffff100372a1d1d
RDX: 1ffff1003a922480 RSI: ffff8801b950e8c8 RDI: ffff8801d4912400
RBP: ffff8801b974fb60 R08: ffff8801b950e8e8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801d49122d8
R13: 0000000000000000 R14: ffff8801d4912280 R15: ffff8801b974fc78
FS:  00007f4be6db7700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001d9607000 CR4: 00000000001606f0
Stack:
 0000000000000201 ffffffff836c5151 ffff8801b974fae0 ffffffff81235c2d
 ffff8801d4912280 ffff8801d4913a58 ffff8801d49122d8 ffff8801d4913a50
 ffff8801d49139b0 ffff8801d49122a0 0000000000000000 0000000000000000
Call Trace:
 [<ffffffff836c8ff7>] 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
 [<ffffffff839fccd3>] 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  [<ffffffff836c3e40>] sock_hold include/net/sock.h:584 [inline]
RIP  [<ffffffff836c3e40>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
 RSP <ffff8801b974fac0>
CR2: 0000000000000080
---[ end trace a6338e349f24cb2e ]---
netlink: 8 bytes leftover after parsing attributes in process `syz-executor6'.