Date:   Thu, 04 Jan 2018 02:58:01 -0800
From:   syzbot <syzbot+56029fd3642567f395f0@...kaller.appspotmail.com>
To:     davem@...emloft.net, kuznet@....inr.ac.ru,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, yoshfuji@...ux-ipv6.org
Subject: KASAN: use-after-free Read in ip6_xmit

Hello,

syzkaller hit the following crash on  
0e08c463db387a2adcb0243b15ab868a73f87807
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+56029fd3642567f395f0@...kaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

audit: type=1400 audit(1514737122.010:7): avc:  denied  { map } for   
pid=3153 comm="syzkaller920384" path="/root/syzkaller920384627" dev="sda1"  
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: use-after-free in ip6_dst_idev include/net/ip6_fib.h:189  
[inline]
BUG: KASAN: use-after-free in ip6_xmit+0x1f92/0x1fc0  
net/ipv6/ip6_output.c:248
Read of size 8 at addr ffff8801ca6f9f18 by task syzkaller920384/3153

CPU: 1 PID: 3153 Comm: syzkaller920384 Not tainted  
4.15.0-rc4-next-20171221+ #78
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:189 [inline]
  ip6_xmit+0x1f92/0x1fc0 net/ipv6/ip6_output.c:248
  inet6_csk_xmit+0x2fc/0x580 net/ipv6/inet6_connection_sock.c:139
  tcp_transmit_skb+0x1b12/0x38b0 net/ipv4/tcp_output.c:1176
  tcp_send_syn_data net/ipv4/tcp_output.c:3456 [inline]
  tcp_connect+0x1ed5/0x4090 net/ipv4/tcp_output.c:3495
  tcp_v4_connect+0x15ef/0x1e70 net/ipv4/tcp_ipv4.c:257
  __inet_stream_connect+0x2d4/0xf00 net/ipv4/af_inet.c:620
  tcp_sendmsg_fastopen net/ipv4/tcp.c:1167 [inline]
  tcp_sendmsg_locked+0x27e4/0x3b30 net/ipv4/tcp.c:1212
  tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1459
  inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:764
  sock_sendmsg_nosec net/socket.c:628 [inline]
  sock_sendmsg+0xca/0x110 net/socket.c:638
  SYSC_sendto+0x361/0x5c0 net/socket.c:1719
  SyS_sendto+0x40/0x50 net/socket.c:1687
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x43fda9
RSP: 002b:00007ffc9b8bd818 EFLAGS: 00000217 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 000000000043fda9
RDX: 0000000000000000 RSI: 0000000020aa1000 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000020aa1000 R09: 0000000000000010
R10: 0000000023ffffff R11: 0000000000000217 R12: 0000000000401710
R13: 00000000004017a0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3140:
  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:3545
  dst_alloc+0x11f/0x1a0 net/core/dst.c:104
  rt_dst_alloc+0xe9/0x520 net/ipv4/route.c:1500
  __mkroute_output net/ipv4/route.c:2242 [inline]
  ip_route_output_key_hash_rcu+0xa40/0x2c10 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+0xa67/0x1240 net/ipv4/datagram.c:51
  __ip6_datagram_connect+0x709/0xf90 net/ipv6/datagram.c:157
  ip6_datagram_connect+0x2f/0x50 net/ipv6/datagram.c:274
  inet_dgram_connect+0x16b/0x1f0 net/ipv4/af_inet.c:542
  SYSC_connect+0x213/0x4a0 net/socket.c:1611
  SyS_connect+0x24/0x30 net/socket.c:1592
  entry_SYSCALL_64_fastpath+0x1f/0x96

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:3489 [inline]
  kmem_cache_free+0x83/0x2a0 mm/slab.c:3747
  dst_destroy+0x219/0x310 net/core/dst.c:140
  dst_destroy_rcu+0x16/0x20 net/core/dst.c:153
  __rcu_reclaim kernel/rcu/rcu.h:172 [inline]
  rcu_do_batch kernel/rcu/tree.c:2675 [inline]
  invoke_rcu_callbacks kernel/rcu/tree.c:2934 [inline]
  __rcu_process_callbacks kernel/rcu/tree.c:2901 [inline]
  rcu_process_callbacks+0xd6c/0x17f0 kernel/rcu/tree.c:2918
  __do_softirq+0x2d7/0xb85 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801ca6f9f00
  which belongs to the cache ip_dst_cache of size 168
The buggy address is located 24 bytes inside of
  168-byte region [ffff8801ca6f9f00, ffff8801ca6f9fa8)
The buggy address belongs to the page:
page:00000000637e5443 count:1 mapcount:0 mapping:0000000000ddf2d5  
index:0xffff8801ca6f9000
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801ca6f9000 ffff8801ca6f9000 000000010000000a
raw: ffff8801d794f138 ffffea0007515320 ffff8801d6d724c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801ca6f9e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ffff8801ca6f9e80: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
> ffff8801ca6f9f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                             ^
  ffff8801ca6f9f80: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc
  ffff8801ca6fa000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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