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BUG: KASAN: slab-out-of-bounds in ip6_dst_idev include/net/ip6_fib.h:192 [inline]
BUG: KASAN: slab-out-of-bounds in ip6_xmit+0x1ce9/0x2090 net/ipv6/ip6_output.c:264
Read of size 8 at addr ffff8801d605c218 by task syzkaller726729/3638

CPU: 0 PID: 3638 Comm: syzkaller726729 Not tainted 4.15.0-rc8-next-20180117+ #99
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23b/0x360 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 ip6_dst_idev include/net/ip6_fib.h:192 [inline]
 ip6_xmit+0x1ce9/0x2090 net/ipv6/ip6_output.c:264
 inet6_csk_xmit+0x2fc/0x580 net/ipv6/inet6_connection_sock.c:139
 l2tp_xmit_core net/l2tp/l2tp_core.c:1099 [inline]
 l2tp_xmit_skb+0x105f/0x1410 net/l2tp/l2tp_core.c:1194
 pppol2tp_sendmsg+0x470/0x670 net/l2tp/l2tp_ppp.c:341
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:640
 ___sys_sendmsg+0x767/0x8b0 net/socket.c:2020
 __sys_sendmsg+0xe5/0x210 net/socket.c:2054
 SYSC_sendmsg net/socket.c:2065 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2061
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x4462f9
RSP: 002b:00007ffdf77899d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000068 RCX: 00000000004462f9
RDX: 0000000000000081 RSI: 000000002037ffc8 RDI: 0000000000000005
RBP: 00000000004a8458 R08: 00000000004a8458 R09: 00000000004a8458
R10: 00000000004a8458 R11: 0000000000000246 R12: 0000000000403430
R13: 00000000004034c0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 0:
(stack is not available)

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801d605c200
 which belongs to the cache ip_dst_cache of size 168
The buggy address is located 24 bytes inside of
 168-byte region [ffff8801d605c200, ffff8801d605c2a8)
The buggy address belongs to the page:
page:ffffea0007581700 count:1 mapcount:0 mapping:ffff8801d605c000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d605c000 0000000000000000 0000000100000010
raw: ffffea0007106120 ffff8801d6f2d848 ffff8801d6fde980 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d605c100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801d605c180: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>ffff8801d605c200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                            ^
 ffff8801d605c280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d605c300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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