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SubjectKASAN: stack-out-of-bounds Read in xfrm_state_find (5)

syzbot hit the following crash on upstream commit
10b84daddbec72c6b440216a69de9a9605127f7a (Sat Mar 31 17:59:00 2018 +0000)
Merge branch 'perf-urgent-for-linus' of
syzbot dashboard link:

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

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BUG: KASAN: stack-out-of-bounds in xfrm_state_find+0x30de/0x3210
Read of size 4 at addr ffff8801b25ef480 by task syzkaller538986/4480

CPU: 0 PID: 4480 Comm: syzkaller538986 Not tainted 4.16.0-rc7+ #9
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+0x194/0x24d lib/dump_stack.c:53
print_address_description+0x73/0x250 mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report+0x23c/0x360 mm/kasan/report.c:412
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
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+0x184/0x28d0 net/xfrm/xfrm_policy.c:1833
xfrm_lookup+0xfcb/0x25c0 net/xfrm/xfrm_policy.c:2163
xfrm_lookup_route+0x39/0x1a0 net/xfrm/xfrm_policy.c:2283
ip_route_output_flow+0x7c/0xa0 net/ipv4/route.c:2583
udp_sendmsg+0x19bd/0x2f70 net/ipv4/udp.c:1012
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:630 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:640
___sys_sendmsg+0x767/0x8b0 net/socket.c:2046
__sys_sendmsg+0xe5/0x210 net/socket.c:2080
SYSC_sendmsg net/socket.c:2091 [inline]
SyS_sendmsg+0x2d/0x50 net/socket.c:2087
do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
RIP: 0033:0x440139
RSP: 002b:00007fffa14c36e8 EFLAGS: 00000217 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440139
RDX: 0000000000000000 RSI: 0000000020000580 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000000000e8 R11: 0000000000000217 R12: 0000000000401a60
R13: 0000000000401af0 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea0006c97bc0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 ffffea0006c90101 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801b25ef380: f2 00 f2 f2 f2 f2 f2 f2 f2 f8 f2 f2 f2 f2 f2 f2
ffff8801b25ef400: f2 00 00 00 00 f2 f2 f2 f2 00 00 00 00 00 00 00
> ffff8801b25ef480: f2 f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 f2 f2
ffff8801b25ef500: f2 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801b25ef580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1

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