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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 ffff8801d086bfd8 by task syz-executor4/10000

CPU: 1 PID: 10000 Comm: syz-executor4 Not tainted 4.15.0-rc8+ #178
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
 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:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
RIP: 0023:0xf7f8ec79
RSP: 002b:00000000f778a08c EFLAGS: 00000296 ORIG_RAX: 0000000000000172
RAX: ffffffffffffffda RBX: 0000000000000018 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 10000:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3544
 dst_alloc+0x11f/0x1a0 net/core/dst.c:107
 rt_dst_alloc+0xe9/0x540 net/ipv4/route.c:1500
 __mkroute_output net/ipv4/route.c:2242 [inline]
 ip_route_output_key_hash_rcu+0xa40/0x2c40 net/ipv4/route.c:2470
 ip_route_output_key_hash+0x20b/0x370 net/ipv4/route.c:2299
 __ip_route_output_key include/net/route.h:125 [inline]
 ip_route_connect include/net/route.h:300 [inline]
 __ip4_datagram_connect+0xa6d/0x1240 net/ipv4/datagram.c:51
 __ip6_datagram_connect+0xbaf/0xf90 net/ipv6/datagram.c:196
 ip6_datagram_connect+0x2f/0x50 net/ipv6/datagram.c:274
 inet_dgram_connect+0x16b/0x1f0 net/ipv4/af_inet.c:541
 SYSC_connect+0x213/0x4a0 net/socket.c:1621
 SyS_connect+0x24/0x30 net/socket.c:1602
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801d086be80
 which belongs to the cache ip_dst_cache of size 216
The buggy address is located 128 bytes to the right of
 216-byte region [ffff8801d086be80, ffff8801d086bf58)
The buggy address belongs to the page:
page:ffffea0007421ac0 count:1 mapcount:0 mapping:ffff8801d086b0c0 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d086b0c0 0000000000000000 000000010000000c
raw: ffffea00071208a0 ffff8801d6f6c948 ffff8801d6f6db00 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d086be80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801d086bf00: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>ffff8801d086bf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                    ^
 ffff8801d086c000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d086c080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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