Date:   Wed, 31 Jan 2018 07:58:01 -0800
From:   syzbot <syzbot+e1a1577ca8bcb47b769a@...kaller.appspotmail.com>
To:     davem@...emloft.net, herbert@...dor.apana.org.au,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        steffen.klassert@...unet.com, syzkaller-bugs@...glegroups.com
Subject: KASAN: stack-out-of-bounds Read in xfrm_state_find (4)

Hello,

syzbot hit the following crash on upstream commit
72906f38934a49faf4d2d38ea9ae32adcf7d5d0c (Tue Jan 30 21:04:50 2018 +0000)
Merge branch 'x86-hyperv-for-linus' of  
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

So far this crash happened 4 times on net-next, upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.
user-space arch: i386

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e1a1577ca8bcb47b769a@...kaller.appspotmail.com
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details.
If you forward the report, please keep this part and the footer.

audit: type=1400 audit(1517389806.479:7): avc:  denied  { map } for   
pid=4152 comm="syzkaller668857" path="/root/syzkaller668857449" 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: stack-out-of-bounds in xfrm_state_find+0x30de/0x3210  
net/xfrm/xfrm_state.c:1051
Read of size 4 at addr ffff8801b37f7940 by task syzkaller668857/4152

CPU: 1 PID: 4152 Comm: syzkaller668857 Not tainted 4.15.0+ #197
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_load4_noabort+0x14/0x20 mm/kasan/report.c:429
  xfrm_state_find+0x30de/0x3210 net/xfrm/xfrm_state.c:1051
  xfrm_tmpl_resolve_one net/xfrm/xfrm_policy.c:1393 [inline]
  xfrm_tmpl_resolve+0x2ee/0xc40 net/xfrm/xfrm_policy.c:1437
  xfrm_resolve_and_create_bundle+0x172/0x2760 net/xfrm/xfrm_policy.c:1828
  xfrm_lookup+0xfcb/0x25d0 net/xfrm/xfrm_policy.c:2158
  xfrm_lookup_route+0x39/0x1a0 net/xfrm/xfrm_policy.c:2278
  ip_route_output_flow+0x7c/0xa0 net/ipv4/route.c:2559
  raw_sendmsg+0xcf2/0x3cf0 net/ipv4/raw.c:640
  inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
  sock_sendmsg_nosec net/socket.c:638 [inline]
  sock_sendmsg+0xca/0x110 net/socket.c:648
  SYSC_sendto+0x361/0x5c0 net/socket.c:1729
  SyS_sendto+0x40/0x50 net/socket.c:1697
  do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
  do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
  entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
RIP: 0023:0xf7fecc79
RSP: 002b:00000000ffadc46c EFLAGS: 00000286 ORIG_RAX: 0000000000000171
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000020098000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020cf9000
RBP: 0000000000000010 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea0006cdfdc0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 0000000100000001 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801b37f7800: f2 f2 f2 f2 f2 00 00 00 f2 f2 f2 f2 f2 00 00 00
  ffff8801b37f7880: 00 f2 f2 f2 f2 00 00 00 00 00 00 f2 f2 f2 f2 f2
> ffff8801b37f7900: f2 00 00 00 00 00 00 00 f2 f2 f2 f2 f2 00 00 00
                                            ^
  ffff8801b37f7980: 00 00 00 00 00 00 f2 f2 f2 00 00 00 00 00 00 00
  ffff8801b37f7a00: 00 00 00 00 00 00 00 f1 f1 f1 f1 00 f2 f2 f2 f3
==================================================================


---
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View attachment "raw.log.txt" of type "text/plain" (15115 bytes)

View attachment "repro.syz.txt" of type "text/plain" (1088 bytes)

View attachment "repro.c.txt" of type "text/plain" (2855 bytes)

View attachment "config.txt" of type "text/plain" (136013 bytes)

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