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BUG: KASAN: slab-out-of-bounds in ip6_dst_idev include/net/ip6_fib.h:187 [inline]
BUG: KASAN: slab-out-of-bounds in ip6_xmit+0x2048/0x2090 net/ipv6/ip6_output.c:256
Read of size 8 at addr ffff8801d4695558 by task syz-executor3/17691

CPU: 1 PID: 17691 Comm: syz-executor3 Not tainted 4.15.0-rc8+ #268
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:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 ip6_dst_idev include/net/ip6_fib.h:187 [inline]
 ip6_xmit+0x2048/0x2090 net/ipv6/ip6_output.c:256
 inet6_csk_xmit+0x2fc/0x580 net/ipv6/inet6_connection_sock.c:139
 l2tp_xmit_core net/l2tp/l2tp_core.c:1105 [inline]
 l2tp_xmit_skb+0x1068/0x1410 net/l2tp/l2tp_core.c:1200
 pppol2tp_sendmsg+0x470/0x670 net/l2tp/l2tp_ppp.c:341
 sock_sendmsg_nosec net/socket.c:638 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:648
 ___sys_sendmsg+0x767/0x8b0 net/socket.c:2028
 __sys_sendmsg+0xe5/0x210 net/socket.c:2062
 SYSC_sendmsg net/socket.c:2073 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2069
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452e99
RSP: 002b:00007f0e973b5c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452e99
RDX: 0000000000000081 RSI: 000000002037ffc8 RDI: 0000000000000014
RBP: 00000000000003db R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f3d28
R13: 00000000ffffffff R14: 00007f0e973b66d4 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 ffff8801d4695540
 which belongs to the cache ip_dst_cache of size 216
The buggy address is located 24 bytes inside of
 216-byte region [ffff8801d4695540, ffff8801d4695618)
The buggy address belongs to the page:
page:ffffea000751a540 count:1 mapcount:0 mapping:ffff8801d4695040 index:0xffff8801d46957c0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d4695040 ffff8801d46957c0 0000000100000009
raw: ffffea0006ef4660 ffff8801d6fcda38 ffff8801d6fce980 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d4695400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801d4695480: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>ffff8801d4695500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                    ^
 ffff8801d4695580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d4695600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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