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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+0x1f76/0x2260 net/ipv6/ip6_output.c:264
Read of size 8 at addr ffff8801c6735418 by task syz-executor4/9229

CPU: 1 PID: 9229 Comm: syz-executor4 Not tainted 4.16.0-rc3+ #246
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+0x194/0x24d 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+0x1f76/0x2260 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:1096 [inline]
 l2tp_xmit_skb+0x105f/0x1410 net/l2tp/l2tp_core.c:1191
 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:2046
 __sys_sendmsg+0xe5/0x210 net/socket.c:2080
 C_SYSC_sendmsg net/compat.c:739 [inline]
 compat_SyS_sendmsg+0x2a/0x40 net/compat.c:737
 do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 do_fast_syscall_32+0x3ec/0xf9f arch/x86/entry/common.c:392
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f3bc99
RSP: 002b:00000000f773709c EFLAGS: 00000286 ORIG_RAX: 0000000000000172
RAX: ffffffffffffffda RBX: 0000000000000016 RCX: 000000002037ffc8
RDX: 0000000000000081 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 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 ffff8801c6735400
 which belongs to the cache ip_dst_cache of size 168
The buggy address is located 24 bytes inside of
 168-byte region [ffff8801c6735400, ffff8801c67354a8)
The buggy address belongs to the page:
page:ffffea000719cd40 count:1 mapcount:0 mapping:ffff8801c6735000 index:0xffff8801c6735000
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801c6735000 ffff8801c6735000 000000010000000e
raw: ffffea00073bfaa0 ffff8801d6bdf238 ffff8801d5401800 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c6735300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801c6735380: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>ffff8801c6735400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                            ^
 ffff8801c6735480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c6735500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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