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audit: type=1400 audit(1516385632.386:184): avc:  denied  { write } for  pid=6536 comm="syz-executor3" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_netfilter_socket permissive=1
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 ffff8801bc835fd8 by task syz-executor2/6532

CPU: 1 PID: 6532 Comm: syz-executor2 Not tainted 4.15.0-rc8+ #268
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
netlink: 'syz-executor4': attribute type 1 has an invalid length.
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
 SYSC_sendmsg net/socket.c:2073 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2069
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452e99
RSP: 002b:00007f7f4b854c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452e99
RDX: 0000000000000081 RSI: 000000002037ffc8 RDI: 0000000000000017
RBP: 0000000000000058 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006ee8e0
R13: 00000000ffffffff R14: 00007f7f4b8556d4 R15: 0000000000000000

Allocated by task 6149:
 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 0:
(stack is not available)

The buggy address belongs to the object at ffff8801bc835e80
 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 [ffff8801bc835e80, ffff8801bc835f58)
The buggy address belongs to the page:
page:ffffea0006f20d40 count:1 mapcount:0 mapping:ffff8801bc8350c0 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bc8350c0 0000000000000000 000000010000000c
raw: ffffea00074e77e0 ffffea0006f2f0e0 ffff8801d6f99800 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bc835e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801bc835f00: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>ffff8801bc835f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                    ^
 ffff8801bc836000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8801bc836080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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