Subject: KASAN: slab-out-of-bounds Read in xfrm_hash_rebuild

From: syzbot <[email-masked]>
Date: Thu, 21 Dec 2017 05:48:01 -0800

syzkaller has found reproducer for the following crash on  
8f36e00065436412a02d1f50ad77375bdb506300
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-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

==================================================================
BUG: KASAN: slab-out-of-bounds in xfrm_hash_rebuild+0xdbe/0xf00  
net/xfrm/xfrm_policy.c:618
Read of size 2 at addr ffff8801c8e92fe4 by task kworker/1:1/23

CPU: 1 PID: 23 Comm: kworker/1:1 Not tainted 4.15.0-rc3+ #161
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events xfrm_hash_rebuild
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_load2_noabort+0x14/0x20 mm/kasan/report.c:428
  xfrm_hash_rebuild+0xdbe/0xf00 net/xfrm/xfrm_policy.c:618
  process_one_work+0xbbf/0x1b10 kernel/workqueue.c:2112
  worker_thread+0x223/0x1990 kernel/workqueue.c:2246
  kthread+0x33c/0x400 kernel/kthread.c:238
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:441

Allocated by task 3152:
  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
  __do_kmalloc mm/slab.c:3708 [inline]
  __kmalloc+0x162/0x760 mm/slab.c:3717
  kmalloc include/linux/slab.h:504 [inline]
  sk_prot_alloc+0x101/0x2a0 net/core/sock.c:1471
  sk_alloc+0x8c/0x730 net/core/sock.c:1525
  pfkey_create+0x2b2/0xae0 net/key/af_key.c:158
  __sock_create+0x4d4/0x850 net/socket.c:1257
  sock_create net/socket.c:1297 [inline]
  SYSC_socket net/socket.c:1327 [inline]
  SyS_socket+0xeb/0x1d0 net/socket.c:1307
  entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801c8e92ac0
  which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1316 bytes inside of
  2048-byte region [ffff8801c8e92ac0, ffff8801c8e932c0)
The buggy address belongs to the page:
page:000000004ba28b34 count:1 mapcount:0 mapping:00000000d439dc9d index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801c8e92240 0000000000000000 0000000100000003
raw: ffffea000723d120 ffff8801db001948 ffff8801db000c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801c8e92e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ffff8801c8e92f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8801c8e92f80: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
                                                        ^
  ffff8801c8e93000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801c8e93080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================