KASAN: use-after-free Read in memcmp

Hello,

syzbot hit the following crash on net-next commit
9515a2e082f91457db0ecff4b65371d0fb5d9aad (Thu Jan 25 03:37:38 2018 +0000)
net/ipv4: Allow send to local broadcast from a socket bound to a VRF

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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Reported-by: syzbot+9c2fa798948a23cdd3f0@syzkaller.appspotmail.com
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==================================================================
BUG: KASAN: use-after-free in memcmp+0xe3/0x160 lib/string.c:861
Read of size 1 at addr ffff8801c026aae0 by task kworker/u4:10/7138

CPU: 1 PID: 7138 Comm: kworker/u4:10 Not tainted 4.15.0-rc9+ #210
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: krdsd rds_send_worker
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_load1_noabort+0x14/0x20 mm/kasan/report.c:427
  memcmp+0xe3/0x160 lib/string.c:861
  memcmp include/linux/string.h:385 [inline]
  rhashtable_compare include/linux/rhashtable.h:612 [inline]
  __rhashtable_lookup include/linux/rhashtable.h:634 [inline]
  rhashtable_lookup include/linux/rhashtable.h:666 [inline]
  rhashtable_lookup_fast include/linux/rhashtable.h:692 [inline]
  rds_find_bound+0x498/0xa10 net/rds/bind.c:63
  rds_recv_incoming+0x582/0x11d0 net/rds/recv.c:360
  rds_loop_xmit+0x149/0x320 net/rds/loop.c:82
  rds_send_xmit+0xa70/0x2480 net/rds/send.c:355
  rds_send_worker+0x115/0x2a0 net/rds/threads.c:199
  process_one_work+0xbbf/0x1b10 kernel/workqueue.c:2113
  worker_thread+0x223/0x1990 kernel/workqueue.c:2247
  kthread+0x33c/0x400 kernel/kthread.c:238
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:541

Allocated by task 11357:
  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
  sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1465
  sk_alloc+0x105/0x1440 net/core/sock.c:1525
  rds_create+0x11c/0x660 net/rds/af_rds.c:535
  __sock_create+0x4d4/0x850 net/socket.c:1285
  sock_create net/socket.c:1325 [inline]
  SYSC_socket net/socket.c:1355 [inline]
  SyS_socket+0xeb/0x1d0 net/socket.c:1335
  entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 11357:
  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
  sk_prot_free net/core/sock.c:1506 [inline]
  __sk_destruct+0x628/0x920 net/core/sock.c:1590
  sk_destruct+0x47/0x80 net/core/sock.c:1598
  __sk_free+0xf1/0x2b0 net/core/sock.c:1609
  sk_free+0x2a/0x40 net/core/sock.c:1620
  sock_put include/net/sock.h:1658 [inline]
  rds_release+0x3a6/0x520 net/rds/af_rds.c:89
  sock_release+0x8d/0x1e0 net/socket.c:595
  sock_close+0x16/0x20 net/socket.c:1149
  __fput+0x327/0x7e0 fs/file_table.c:210
  ____fput+0x15/0x20 fs/file_table.c:244
  task_work_run+0x199/0x270 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
  exit_to_usermode_loop+0x296/0x310 arch/x86/entry/common.c:162
  prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
  syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
  entry_SYSCALL_64_fastpath+0x9e/0xa0

The buggy address belongs to the object at ffff8801c026a680
  which belongs to the cache RDS of size 1472
The buggy address is located 1120 bytes inside of
  1472-byte region [ffff8801c026a680, ffff8801c026ac40)
The buggy address belongs to the page:
page:ffffea0007009a80 count:1 mapcount:0 mapping:ffff8801c026a040 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801c026a040 0000000000000000 0000000100000005
raw: ffffea0006fe95a0 ffffea0006f689a0 ffff8801d2d22200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801c026a980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801c026aa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

ffff8801c026aa80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

                                                        ^
  ffff8801c026ab00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801c026ab80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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