KASAN: stack-out-of-bounds Read in memcmp

Hello,

syzkaller hit the following crash on  
bcecb4bbf88aa03171c30652bca761cf27755a6b
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.
Unfortunately, I don't have any reproducer for this bug yet.


IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1dfda02bdf25a814ceb7@syzkaller.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.

==================================================================
BUG: KASAN: stack-out-of-bounds in memcmp+0xe3/0x160 lib/string.c:861
Read of size 1 at addr ffff8801c19175d0 by task syz-executor6/18562

CPU: 0 PID: 18562 Comm: syz-executor6 Not tainted 4.15.0-rc5+ #172
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_load1_noabort+0x14/0x20 mm/kasan/report.c:427
  memcmp+0xe3/0x160 lib/string.c:861
  memcmp include/linux/string.h:385 [inline]
  addr_match include/net/xfrm.h:873 [inline]
  __xfrm6_selector_match net/xfrm/xfrm_policy.c:90 [inline]
  xfrm_selector_match+0x1bc/0xe00 net/xfrm/xfrm_policy.c:104
  xfrm_state_look_at.constprop.30+0x113/0x360 net/xfrm/xfrm_state.c:909
  xfrm_state_find+0x1595/0x3210 net/xfrm/xfrm_state.c:977
  xfrm_tmpl_resolve_one net/xfrm/xfrm_policy.c:1394 [inline]
  xfrm_tmpl_resolve+0x2ee/0xc40 net/xfrm/xfrm_policy.c:1438
  xfrm_resolve_and_create_bundle+0x184/0x28d0 net/xfrm/xfrm_policy.c:1829
  xfrm_lookup+0x15b2/0x24f0 net/xfrm/xfrm_policy.c:2155
  xfrm_lookup_route+0x39/0x1a0 net/xfrm/xfrm_policy.c:2273
  ip_route_output_flow+0x7c/0xa0 net/ipv4/route.c:2559
  udp_sendmsg+0x19d3/0x2ce0 net/ipv4/udp.c:999
  udpv6_sendmsg+0x757/0x3400 net/ipv6/udp.c:1156
  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
  ___sys_sendmsg+0x767/0x8b0 net/socket.c:2018
  __sys_sendmsg+0xe5/0x210 net/socket.c:2052
  SYSC_sendmsg net/socket.c:2063 [inline]
  SyS_sendmsg+0x2d/0x50 net/socket.c:2059
  entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x452ac9
RSP: 002b:00007f6372138c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452ac9
RDX: 0000000000000000 RSI: 00000000201f1000 RDI: 0000000000000013
RBP: 00000000000004a8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f5060
R13: 00000000ffffffff R14: 00007f63721396d4 R15: 0000000000000000

The buggy address belongs to the page:
page:00000000f9ea28ea count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 dead000000000200 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801c1917480: f1 f1 f1 04 f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2 f2
  ffff8801c1917500: f2 f2 f2 f8 f2 f2 f2 f2 f2 f2 f2 00 00 00 00 f2

ffff8801c1917580: f2 f2 f2 00 00 00 00 00 00 00 f2 f2 f2 f2 f2 00

                                                  ^
  ffff8801c1917600: 00 00 00 00 00 00 00 00 f2 f2 f2 00 00 00 00 00
  ffff8801c1917680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@googlegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is  
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug  
report.
Note: all commands must start from beginning of the line in the email body.