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: [<ffffffff836c8f30>] sock_hold include/net/sock.h:584 [inline]
IP: [<ffffffff836c8f30>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
PGD 1c5f92067 [   32.033093] PUD 1cbb9e067 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4971 Comm: syz-executor0 Not tainted 4.9.123-g7fa8c15 #32
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801ca189800 task.stack: ffff8801c2990000
RIP: 0010:[<ffffffff836c8f30>]  [<ffffffff836c8f30>] sock_hold include/net/sock.h:584 [inline]
RIP: 0010:[<ffffffff836c8f30>]  [<ffffffff836c8f30>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
RSP: 0018:ffff8801c2997ab0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801c97cac80 RCX: 1ffff1003943141d
RDX: 1ffff10038db47a0 RSI: ffff8801ca18a0c8 RDI: ffff8801c6da3d00
RBP: ffff8801c2997b50 R08: ffff8801ca18a0e8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c6da3bd8
R13: 0000000000000000 R14: ffff8801c6da3b80 R15: ffff8801c2997c68
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:00000000f77d2b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001c5f95000 CR4: 00000000001606f0
Stack:
 0000000000000201 ffffffff836ca241 ffff8801c2997ad0 ffffffff81237f0d
 ffff8801c6da3b80 ffff8801c97cadd8 ffff8801c6da3bd8 ffff8801c97cadd0
 ffff8801c97cad30 ffff8801c6da3ba0 0000000000000000 0000000000000000
Call Trace:
 [<ffffffff836ce0e7>] pppol2tp_connect+0x10d7/0x18f0 net/l2tp/l2tp_ppp.c:718
 [<ffffffff8301ea38>] SYSC_connect+0x1b8/0x300 net/socket.c:1575
 [<ffffffff83021314>] SyS_connect+0x24/0x30 net/socket.c:1556
 [<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
 [<ffffffff83a03490>] 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  [<ffffffff836c8f30>] sock_hold include/net/sock.h:584 [inline]
RIP  [<ffffffff836c8f30>] l2tp_session_create+0xc60/0x16f0 net/l2tp/l2tp_core.c:1911
 RSP <ffff8801c2997ab0>
CR2: 0000000000000080
---[ end trace 18cf1248859e5cc6 ]---