l2tp_core: tunl 4: sockfd_lookup(fd=6) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=6) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=6) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=6) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=6) returned -9
BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff836c7e40>] sock_hold include/net/sock.h:584 [inline]
IP: [<ffffffff836c7e40>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
PGD 1cb4cf067 [   38.563902] PUD 1cb464067 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4903 Comm: syz-executor0 Not tainted 4.9.122-g54068d6 #30
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801c7c73000 task.stack: ffff8801c7f40000
RIP: 0010:[<ffffffff836c7e40>]  [<ffffffff836c7e40>] sock_hold include/net/sock.h:584 [inline]
RIP: 0010:[<ffffffff836c7e40>]  [<ffffffff836c7e40>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
RSP: 0018:ffff8801c7f47ab0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801c89c0a00 RCX: 1ffff10038f8e71d
RDX: 1ffff10039138120 RSI: ffff8801c7c738c8 RDI: ffff8801c89c0900
RBP: ffff8801c7f47b50 R08: ffff8801c7c738e8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c89c07d8
R13: 0000000000000000 R14: ffff8801c89c0780 R15: ffff8801c7f47c68
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:00000000f7714b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001d01ec000 CR4: 00000000001606f0
Stack:
 0000000000000201 ffffffff836c9151 ffff8801c7f47ad0 ffffffff81237ecd
 ffff8801c89c0780 ffff8801c89c0b58 ffff8801c89c07d8 ffff8801c89c0b50
 ffff8801c89c0ab0 ffff8801c89c07a0 0000000000000000 0000000000000000
Call Trace:
 [<ffffffff836ccff7>] pppol2tp_connect+0x10d7/0x18f0 net/l2tp/l2tp_ppp.c:718
 [<ffffffff8301d958>] SYSC_connect+0x1b8/0x300 net/socket.c:1563
 [<ffffffff83020224>] SyS_connect+0x24/0x30 net/socket.c:1544
 [<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
 [<ffffffff83a023d0>] 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  [<ffffffff836c7e40>] sock_hold include/net/sock.h:584 [inline]
RIP  [<ffffffff836c7e40>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
 RSP <ffff8801c7f47ab0>
CR2: 0000000000000080
---[ end trace c6a3144b2bbb7c21 ]---