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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 ffff8801d8cfffd8 by task syz-executor7/14062

CPU: 0 PID: 14062 Comm: syz-executor7 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
 SYSC_sendto+0x361/0x5c0 net/socket.c:1729
 SyS_sendto+0x40/0x50 net/socket.c:1697
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452e99
RSP: 002b:00007f717a695c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f717a696700 RCX: 0000000000452e99
RDX: 0000000000000fff RSI: 0000000020de7000 RDI: 0000000000000014
RBP: 0000000000000000 R08: 000000002064eff0 R09: 0000000000000010
R10: c3fe68eda9554f8b R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a2f7ef R14: 00007f717a6969c0 R15: 0000000000000000

Allocated by task 13885:
 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_output_key include/net/route.h:135 [inline]
 sctp_v4_get_dst+0x5fa/0x1690 net/sctp/protocol.c:458
 sctp_transport_route+0xa8/0x430 net/sctp/transport.c:293
 sctp_assoc_add_peer+0x4fe/0x1100 net/sctp/associola.c:655
 sctp_process_param net/sctp/sm_make_chunk.c:2529 [inline]
 sctp_process_init+0x1a33/0x2390 net/sctp/sm_make_chunk.c:2345
 sctp_sf_do_unexpected_init.isra.28+0x73d/0x13b0 net/sctp/sm_statefuns.c:1516
 sctp_sf_do_5_2_1_siminit+0x35/0x40 net/sctp/sm_statefuns.c:1645
 sctp_do_sm+0x18a/0x6a20 net/sctp/sm_sideeffect.c:1190
 sctp_assoc_bh_rcv+0x283/0x4b0 net/sctp/associola.c:1065
 sctp_inq_push+0x23b/0x300 net/sctp/inqueue.c:95
 sctp_backlog_rcv+0x177/0xaa0 net/sctp/input.c:350
 sk_backlog_rcv include/net/sock.h:907 [inline]
 __release_sock+0x124/0x360 net/core/sock.c:2264
 release_sock+0xa4/0x2a0 net/core/sock.c:2779
 sctp_wait_for_connect+0x346/0x570 net/sctp/socket.c:8167
 sctp_sendmsg+0x2a28/0x3420 net/sctp/socket.c:2050
 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 7008:
 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 ffff8801d8cffe80
 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 [ffff8801d8cffe80, ffff8801d8cfff58)
The buggy address belongs to the page:
page:ffffea0007633fc0 count:1 mapcount:0 mapping:ffff8801d8cff0c0 index:0xffff8801d8cffac0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d8cff0c0 ffff8801d8cffac0 0000000100000007
raw: ffffea0006f3aea0 ffffea00074572e0 ffff8801d6fdf4c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d8cffe80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801d8cfff00: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>ffff8801d8cfff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                    ^
 ffff8801d8d00000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d8d00080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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