syzbot

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 3811 Comm: syzkaller169665 Not tainted 4.9.80-g8a174b47 #39
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801c0f24800 task.stack: ffff8801d7828000
RIP: 0010:[<ffffffff8341fa26>]  [<ffffffff8341fa26>] ip6_xmit+0xb16/0x1b70 net/ipv6/ip6_output.c:254
RSP: 0018:ffff8801d782f6c0  EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff8801d8510640 RCX: ffffffff8341f9ec
RDX: ffff8801d85106b8 RSI: ffffffff844de160 RDI: ffff8801d6a1d818
RBP: ffff8801d782f8d8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801ceaf7180
R13: 00000000000005b4 R14: ffff8801d99044e4 R15: 0000000000000040
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:000000000933b840
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000020ea7ff8 CR3: 00000001d9858000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d782f6d0 ffffffff8107c736 ffff8801d782f710 ffffffff81235370
 ffffffff81236a01 0000001200000001 0000000000000000 1ffff1003af05ee6
 ffff8801d8510708 ffff8801d8510698 ffff8801d85106b8 ffff8801ba319380
Call Trace:
 [<ffffffff834e60ed>] inet6_csk_xmit+0x27d/0x4d0 net/ipv6/inet6_connection_sock.c:178
 [<ffffffff8358250c>] l2tp_xmit_core net/l2tp/l2tp_core.c:1178 [inline]
 [<ffffffff8358250c>] l2tp_xmit_skb+0xcdc/0xf50 net/l2tp/l2tp_core.c:1273
 [<ffffffff8358e280>] pppol2tp_sendmsg+0x5c0/0x7a0 net/l2tp/l2tp_ppp.c:339
 [<ffffffff82ed7baa>] sock_sendmsg_nosec net/socket.c:635 [inline]
 [<ffffffff82ed7baa>] sock_sendmsg+0xca/0x110 net/socket.c:645
 [<ffffffff82ed97a1>] ___sys_sendmsg+0x6d1/0x7e0 net/socket.c:1969
 [<ffffffff82edb7d6>] __sys_sendmsg+0xd6/0x190 net/socket.c:2003
 [<ffffffff82fde04a>] C_SYSC_sendmsg net/compat.c:734 [inline]
 [<ffffffff82fde04a>] compat_SyS_sendmsg+0x2a/0x40 net/compat.c:732
 [<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
 [<ffffffff838b4db4>] entry_SYSENTER_compat+0x74/0x83 arch/x86/entry/entry_64_compat.S:127
Code: fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 4a 10 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 54 24 50 4d 8b a4 24 18 03 00 00 <65> 49 ff 44 24 28 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 03 0f 
RIP  [<ffffffff8341fa26>] ip6_xmit+0xb16/0x1b70 net/ipv6/ip6_output.c:254
 RSP <ffff8801d782f6c0>
---[ end trace fcbcf31dffa0ef0d ]---
Kernel panic - not syncing: Fatal exception in interrupt
Dumping ftrace buffer:
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Kernel Offset: disabled
Rebooting in 86400 seconds..