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BUG: KASAN: slab-out-of-bounds in ip6_dst_idev include/net/ip6_fib.h:141 [inline]
BUG: KASAN: slab-out-of-bounds in ip6_xmit+0x1838/0x1b80 net/ipv6/ip6_output.c:254
Read of size 8 at addr ffff8801cb517658 by task syz-executor1/6577

CPU: 0 PID: 6577 Comm: syz-executor1 Not tainted 4.9.124-g09eb2ba #83
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801bf657540 ffffffff81eb95e9 ffffea00072d45c0 ffff8801cb517658
 0000000000000000 ffff8801cb517658 0000000000000040 ffff8801bf657578
 ffffffff8156c35e ffff8801cb517658 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
 [<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

Allocated by task 0:
(stack is not available)

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801cb517640
 which belongs to the cache ip_dst_cache of size 216
The buggy address is located 24 bytes inside of
 216-byte region [ffff8801cb517640, ffff8801cb517718)
The buggy address belongs to the page:
page:ffffea00072d45c0 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0x8000000000000080(slab)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cb517500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801cb517580: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>ffff8801cb517600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                    ^
 ffff8801cb517680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801cb517700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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