==================================================================
BUG: KASAN: use-after-free in ip6_dst_idev include/net/ip6_fib.h:141 [inline]
BUG: KASAN: use-after-free in ip6_xmit+0x1838/0x1b80 net/ipv6/ip6_output.c:254
Read of size 8 at addr ffff8801ce0d1158 by task syz-executor5/20201

CPU: 1 PID: 20201 Comm: syz-executor5 Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801bd26f540 ffffffff81eb95e9 ffffea0007383440 ffff8801ce0d1158
 0000000000000000 ffff8801ce0d1158 0000000000000040 ffff8801bd26f578
 ffffffff8156c35e ffff8801ce0d1158 0000000000000008 0000000000000000
Call Trace:
 [<ffffffff81eb95e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb95e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8156c35e>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff8156c768>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff8156c768>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff8153faf4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 [<ffffffff83562358>] ip6_dst_idev include/net/ip6_fib.h:141 [inline]
 [<ffffffff83562358>] ip6_xmit+0x1838/0x1b80 net/ipv6/ip6_output.c:254
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: 20217 Comm: syz-executor1 Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff880197f08000 task.stack: ffff8801994f0000
RIP: 0010:[<ffffffff8356164d>]  [<ffffffff8356164d>] ip6_xmit+0xb2d/0x1b80 net/ipv6/ip6_output.c:254
RSP: 0018:ffff8801994f75e0  EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff88019b990140 RCX: ffffc900001e8000
RDX: ffff88019b9901b8 RSI: ffffffff83561613 RDI: ffff8801cccca518
RBP: ffff8801994f77f8 R08: ffffed003329eef2 R09: ffff8801994f7750
R10: ffffed003329eef1 R11: 0000000000000003 R12: ffff8801c5ae6880
R13: ffff8801da017ae6 R14: 000000000000001b R15: 0000000000000040
FS:  00007f82ff07c700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32f28000 CR3: 00000001cd1dd000 CR4: 00000000001606f0
DR0: 0001000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Stack:
 ffff8801994f7638 ffffffff8100301a 0000000000000001 ffffed0043fffa01
 0000001000000001 0000000000000000 1ffff1003329eeca ffff88019b990208
 ffff88019b990198 ffff88019b9901b8 ffff88019b0cce00 ffff8801b9870000
Call Trace:
 [<ffffffff836275ec>] inet6_csk_xmit+0x27c/0x4d0 net/ipv6/inet6_connection_sock.c:178
 [<ffffffff836c42e5>] l2tp_xmit_core net/l2tp/l2tp_core.c:1178 [inline]
 [<ffffffff836c42e5>] l2tp_xmit_skb+0xc45/0xf30 net/l2tp/l2tp_core.c:1273
 [<ffffffff836cf8b0>] pppol2tp_sendmsg+0x4e0/0x790 net/l2tp/l2tp_ppp.c:339
 [<ffffffff8301e0ac>] sock_sendmsg_nosec net/socket.c:648 [inline]
 [<ffffffff8301e0ac>] sock_sendmsg+0xcc/0x110 net/socket.c:658
 [<ffffffff8301f8ca>] ___sys_sendmsg+0x47a/0x840 net/socket.c:1982
 [<ffffffff83021e31>] __sys_sendmmsg+0x161/0x3d0 net/socket.c:2072
 [<ffffffff830220d5>] SYSC_sendmmsg net/socket.c:2103 [inline]
 [<ffffffff830220d5>] SyS_sendmmsg+0x35/0x60 net/socket.c:2098
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 55 0e 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 54 24 48 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  [<ffffffff8356164d>] ip6_xmit+0xb2d/0x1b80 net/ipv6/ip6_output.c:254
 RSP <ffff8801994f75e0>
---[ end trace a9fd49725f8453c7 ]---