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

[syzbot]

Hello,

syzkaller hit the following crash on
4b24dd8022801ef75f1ce322ff2f83a51900ab5b
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.
CC: [da...@davemloft.net her...@gondor.apana.org.au
linux-...@vger.kernel.org net...@vger.kernel.org
steffen....@secunet.com]

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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 ffff8801c4f175e4 by task syz-executor2/2549

CPU: 1 PID: 2549 Comm: syz-executor2 Not tainted 4.15.0-rc5+ #174
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_load2_noabort+0x14/0x20 mm/kasan/report.c:428
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: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:00007f14527b0c58 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: 00007f14527b16d4 R15: 0000000000000000

The buggy address belongs to the page:
page:000000009523cdf8 count:0 mapcount:0 mapping: (null) index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: dead000000000100 dead000000000200 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801c4f17480: f1 f1 f1 04 f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2 f2
ffff8801c4f17500: f2 f2 f2 f8 f2 f2 f2 f2 f2 f2 f2 00 00 00 00 f2
> ffff8801c4f17580: f2 f2 f2 00 00 00 00 00 00 00 f2 f2 f2 f2 f2 00
^
ffff8801c4f17600: 00 00 00 00 00 00 00 00 f2 f2 f2 00 00 00 00 00
ffff8801c4f17680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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[Dmitry Vyukov]

#syz fix:
xfrm: Fix stack-out-of-bounds with misconfigured transport mode policies.

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