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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 ffff8801be9fff18 by task syz-executor0/11922

CPU: 0 PID: 11922 Comm: syz-executor0 Not tainted 4.15.0-rc8+ #267
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
 SYSC_sendto+0x361/0x5c0 net/socket.c:1729
 SyS_sendto+0x40/0x50 net/socket.c:1697
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452e39
RSP: 002b:00007f6aee749c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452e39
RDX: 0000000000000fff RSI: 0000000020de7000 RDI: 0000000000000014
RBP: 0000000000000056 R08: 000000002064eff0 R09: 0000000000000010
R10: c3fe68eda9554f8b R11: 0000000000000212 R12: 00000000006ee8b0
R13: 00000000ffffffff R14: 00007f6aee74a6d4 R15: 0000000000000000

Allocated by task 8427:
 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_output_flow+0x26/0xa0 net/ipv4/route.c:2553
 ip_route_connect include/net/route.h:307 [inline]
 tcp_v4_connect+0x77b/0x1e80 net/ipv4/tcp_ipv4.c:175
 __inet_stream_connect+0x2d4/0xf00 net/ipv4/af_inet.c:619
 tcp_sendmsg_fastopen net/ipv4/tcp.c:1169 [inline]
 tcp_sendmsg_locked+0x280e/0x3b60 net/ipv4/tcp.c:1214
 tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1461
 inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
 sock_sendmsg_nosec net/socket.c:638 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:648
 SYSC_sendto+0x361/0x5c0 net/socket.c:1729
 SyS_sendto+0x40/0x50 net/socket.c:1697
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 0:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3488 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3746
 dst_destroy+0x216/0x330 net/core/dst.c:138
 dst_destroy_rcu+0x16/0x20 net/core/dst.c:151
 __rcu_reclaim kernel/rcu/rcu.h:195 [inline]
 rcu_do_batch kernel/rcu/tree.c:2758 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:3012 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2979 [inline]
 rcu_process_callbacks+0xd6c/0x17f0 kernel/rcu/tree.c:2996
 __do_softirq+0x2d7/0xb85 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801be9ffdc0
 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 [ffff8801be9ffdc0, ffff8801be9ffe98)
The buggy address belongs to the page:
page:ffffea0006fa7fc0 count:1 mapcount:0 mapping:ffff8801be9ff000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801be9ff000 0000000000000000 000000010000000c
raw: ffffea00072dea60 ffffea0007054e60 ffff8801d6fbb4c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801be9ffe00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801be9ffe80: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801be9fff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                            ^
 ffff8801be9fff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801bea00000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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