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

From: syzbot <[email-masked]>
Date: Tue, 07 Nov 2017 12:28:24 -0800

Hello,

syzkaller hit the following crash on  
0f611fb6dcc0d6d91b4e1fec911321f434a3b858
git://git.cmpxchg.org/linux-mmots.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output 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:619
Read of size 2 at addr ffff8801d180fa34 by task kworker/1:2/1348

CPU: 1 PID: 1348 Comm: kworker/1:2 Not tainted 4.14.0-rc5-mm1+ #20
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:16 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:52
  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:619
  process_one_work+0xbf0/0x1bc0 kernel/workqueue.c:2112
  worker_thread+0x223/0x1990 kernel/workqueue.c:2246
  kthread+0x38b/0x470 kernel/kthread.c:242
  ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

Allocated by task 3006:
  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:3712 [inline]
  __kmalloc+0x162/0x760 mm/slab.c:3721
  kmalloc include/linux/slab.h:504 [inline]
  sk_prot_alloc+0x101/0x2a0 net/core/sock.c:1469
  sk_alloc+0x89/0x700 net/core/sock.c:1523
  pfkey_create+0x2b2/0xae0 net/key/af_key.c:158
  __sock_create+0x4d4/0x850 net/socket.c:1261
  sock_create net/socket.c:1301 [inline]
  SYSC_socket net/socket.c:1331 [inline]
  SyS_socket+0xeb/0x200 net/socket.c:1311
  entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801d180f500
  which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1332 bytes inside of
  2048-byte region [ffff8801d180f500, ffff8801d180fd00)
The buggy address belongs to the page:
page:ffffea0007460380 count:1 mapcount:0 mapping:ffff8801d180e400 index:0x0  
compound_mapcount: 0
flags: 0x200000000008100(slab|head)
raw: 0200000000008100 ffff8801d180e400 0000000000000000 0000000100000003
raw: ffffea0007490720 ffff8801dac01948 ffff8801dac00c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d180f900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ffff8801d180f980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8801d180fa00: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
                                      ^
  ffff8801d180fa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d180fb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

---
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