l2tp_core: tunl 2: sockfd_lookup(fd=5) returned -9
l2tp_core: tunl 2: sockfd_lookup(fd=6) returned -9
l2tp_core: tunl 2: sockfd_lookup(fd=5) returned -9
l2tp_core: tunl 2: sockfd_lookup(fd=6) returned -9
BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: [<ffffffff835868b2>] sock_hold include/net/sock.h:584 [inline]
IP: [<ffffffff835868b2>] l2tp_session_create+0xc42/0x1770 net/l2tp/l2tp_core.c:1907
PGD 80000001c74ab067 
PUD 1c74ac067 
PMD 0 

Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 3776 Comm: syzkaller109062 Not tainted 4.9.78-ge9dabe6 #28
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801c8b76000 task.stack: ffff8801c7510000
RIP: 0010:[<ffffffff835868b2>]  [<ffffffff835868b2>] sock_hold include/net/sock.h:584 [inline]
RIP: 0010:[<ffffffff835868b2>]  [<ffffffff835868b2>] l2tp_session_create+0xc42/0x1770 net/l2tp/l2tp_core.c:1907
RSP: 0018:ffff8801c7517ab0  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801c7709180 RCX: 0000000000000006
RDX: 1ffff1003912cc30 RSI: ffff8801c8b768b0 RDI: ffff8801c8966180
RBP: ffff8801c7517b50 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c8966058
R13: 0000000000007fff R14: 0000000000000000 R15: ffff8801c8966000
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:00000000f774db40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000000000080 CR3: 00000001c8166000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000201 ffffffff83587c6e ffff8801c7517ad0 ffffffff8123b7fd
 ffff8801c8966000 ffff8801c8966058 ffff8801c77092d8 ffff8801c77092d0
 ffff8801c7709230 ffff8801c8966020 0000000000000000 ffff8801c89660e0
Call Trace:
 [<ffffffff8358bd0e>] pppol2tp_connect+0x10fe/0x18f0 net/l2tp/l2tp_ppp.c:711
 [<ffffffff82ed86e6>] SYSC_connect+0x1b6/0x310 net/socket.c:1562
 [<ffffffff82edaf44>] SyS_connect+0x24/0x30 net/socket.c:1543
 [<ffffffff81006fc7>] do_syscall_32_irqs_on arch/x86/entry/common.c:322 [inline]
 [<ffffffff81006fc7>] do_fast_syscall_32+0x2f7/0x890 arch/x86/entry/common.c:384
 [<ffffffff838b4534>] entry_SYSENTER_compat+0x74/0x83 arch/x86/entry/entry_64_compat.S:127
Code: 00 00 49 8d bf 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 d8 08 00 00 49 8b 87 80 01 00 00 <f0> ff 80 80 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 55 c8 
RIP  [<ffffffff835868b2>] sock_hold include/net/sock.h:584 [inline]
RIP  [<ffffffff835868b2>] l2tp_session_create+0xc42/0x1770 net/l2tp/l2tp_core.c:1907
 RSP <ffff8801c7517ab0>
CR2: 0000000000000080
---[ end trace 21266c293fffb4fc ]---