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BUG: KASAN: stack-out-of-bounds in xfrm_flowi_dport include/net/xfrm.h:932 [inline]
BUG: KASAN: stack-out-of-bounds in __xfrm6_selector_match net/xfrm/xfrm_policy.c:91 [inline]
BUG: KASAN: stack-out-of-bounds in xfrm_selector_match+0xcdc/0xe00 net/xfrm/xfrm_policy.c:104
Read of size 2 at addr ffff8801a3de7494 by task syz-executor2/15012

CPU: 1 PID: 15012 Comm: syz-executor2 Not tainted 4.15.0-rc7-next-20180110+ #93
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:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23b/0x360 mm/kasan/report.c:412
 __asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:431
 xfrm_flowi_dport include/net/xfrm.h:932 [inline]
 __xfrm6_selector_match net/xfrm/xfrm_policy.c:91 [inline]
 xfrm_selector_match+0xcdc/0xe00 net/xfrm/xfrm_policy.c:104
 xfrm_state_look_at.constprop.30+0x113/0x360 net/xfrm/xfrm_state.c:910
 xfrm_state_find+0x1595/0x3210 net/xfrm/xfrm_state.c:978
 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:1830
 xfrm_lookup+0x15b2/0x24f0 net/xfrm/xfrm_policy.c:2156
 xfrm_lookup_route+0x39/0x1a0 net/xfrm/xfrm_policy.c:2274
 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
 do_syscall_64+0x273/0x920 arch/x86/entry/common.c:285
 entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x452ac9
RSP: 002b:00007ff1f29e8c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452ac9
RDX: 0000000000000000 RSI: 00000000201f1000 RDI: 0000000000000013
RBP: 0000000000000473 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f4b68
R13: 00000000ffffffff R14: 00007ff1f29e96d4 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea00068f79c0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 ffffea00068f0101 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801a3de7380: f2 00 f2 f2 f2 f2 f2 f2 f2 f8 f2 f2 f2 f2 f2 f2
 ffff8801a3de7400: f2 00 00 00 00 f2 f2 f2 f2 00 00 00 00 00 00 00
>ffff8801a3de7480: f2 f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 f2 f2
                         ^
 ffff8801a3de7500: f2 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801a3de7580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1
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