BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff836c2d90>] sock_hold include/net/sock.h:584 [inline]
IP: [<ffffffff836c2d90>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
PGD 1bf504067 [  263.144325] PUD 1be434067 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 19925 Comm: syz-executor1 Not tainted 4.9.116-g0137ea2 #22
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801a56f9800 task.stack: ffff8801d07e0000
RIP: 0010:[<ffffffff836c2d90>]  [<ffffffff836c2d90>] sock_hold include/net/sock.h:584 [inline]
RIP: 0010:[<ffffffff836c2d90>]  [<ffffffff836c2d90>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
RSP: 0018:ffff8801d07e7ab0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801c8c42a00 RCX: 1ffff10034adf41d
RDX: 1ffff10039188750 RSI: ffff8801a56fa0c8 RDI: ffff8801c8c43a80
TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
RBP: ffff8801d07e7b50 R08: ffff8801a56fa0e8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c8c43958
R13: 0000000000000000 R14: ffff8801c8c43900 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f5799b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001c6037000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff836c3007 ffffffff836c40a1 ffff8801a782bb48 0000000000000000
 ffff8801c8c43900 ffff8801c8c42b58 ffff8801c8c43958 ffff8801c8c42b50
 ffff8801c8c42ab0 ffff8801c8c43920 ffff8801a782b300 0000000000000000
Call Trace:
 [<ffffffff836c7f47>] pppol2tp_connect+0x10d7/0x18f0 net/l2tp/l2tp_ppp.c:718
 [<ffffffff83018958>] SYSC_connect+0x1b8/0x300 net/socket.c:1562
 [<ffffffff8301b224>] SyS_connect+0x24/0x30 net/socket.c:1543
 [<ffffffff81006da7>] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 [<ffffffff81006da7>] do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 [<ffffffff839fd310>] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137
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  [<ffffffff836c2d90>] sock_hold include/net/sock.h:584 [inline]
RIP  [<ffffffff836c2d90>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
 RSP <ffff8801d07e7ab0>
CR2: 0000000000000080
BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff836be91c>] l2tp_session_free+0x11c/0x200 net/l2tp/l2tp_core.c:1765
PGD 1bf504067 [  263.523736] PUD 1be434067 
Oops: 0002 [#2] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
---[ end trace 66de93e84090125a ]---