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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 ffff8801bce39fd8 by task syzkaller836552/3646

CPU: 1 PID: 3646 Comm: syzkaller836552 Not tainted 4.15.0-rc7+ #261
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
 tcp_transmit_skb+0x1b1b/0x38c0 net/ipv4/tcp_output.c:1176
 tcp_send_syn_data net/ipv4/tcp_output.c:3459 [inline]
 tcp_connect+0x1e79/0x3fb0 net/ipv4/tcp_output.c:3498
 tcp_v4_connect+0x15f5/0x1e80 net/ipv4/tcp_ipv4.c:257
 __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
 ___sys_sendmsg+0x320/0x8b0 net/socket.c:2028
 __sys_sendmmsg+0x1ee/0x620 net/socket.c:2118
 SYSC_sendmmsg net/socket.c:2149 [inline]
 SyS_sendmmsg+0x35/0x60 net/socket.c:2144
 entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x43fdd9
RSP: 002b:00007ffd67555e68 EFLAGS: 00000217 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fdd9
RDX: 0000000000000001 RSI: 00000000205f8fc8 RDI: 0000000000000004
RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020000000 R11: 0000000000000217 R12: 0000000000401740
R13: 00000000004017d0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3646:
 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
 ___sys_sendmsg+0x320/0x8b0 net/socket.c:2028
 __sys_sendmmsg+0x1ee/0x620 net/socket.c:2118
 SYSC_sendmmsg net/socket.c:2149 [inline]
 SyS_sendmmsg+0x35/0x60 net/socket.c:2144
 entry_SYSCALL_64_fastpath+0x23/0x9a

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801bce39e80
 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 [ffff8801bce39e80, ffff8801bce39f58)
The buggy address belongs to the page:
page:ffffea0006f38e40 count:1 mapcount:0 mapping:ffff8801bce390c0 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bce390c0 0000000000000000 000000010000000c
raw: ffffea0007110160 ffff8801d6f87d48 ffff8801d6f86980 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bce39e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801bce39f00: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>ffff8801bce39f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                    ^
 ffff8801bce3a000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8801bce3a080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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