KASAN: slab-out-of-bounds Read in xfrm_policy_insert_list

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 8d008e64a2eb mISDN: hfcsusb: Use struct_size() in kzalloc()
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=164f0107400000
kernel config: https://syzkaller.appspot.com/x/.config?x=7308e68273924137
dashboard link: https://syzkaller.appspot.com/bug?extid=071bdf2137f3025fb82b
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+071bdf...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in xfrm_policy_insert_list+0xd32/0xfb0
net/xfrm/xfrm_policy.c:1532
Read of size 1 at addr ffff8880a57d0699 by task syz-executor0/22062

CPU: 0 PID: 22062 Comm: syz-executor0 Not tainted 4.20.0+ #18
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
__asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:132
xfrm_policy_insert_list+0xd32/0xfb0 net/xfrm/xfrm_policy.c:1532
xfrm_policy_inexact_insert+0x155/0xda0 net/xfrm/xfrm_policy.c:1195
xfrm_policy_insert+0x623/0x910 net/xfrm/xfrm_policy.c:1570
xfrm_add_policy+0x2a1/0x6c0 net/xfrm/xfrm_user.c:1657
xfrm_user_rcv_msg+0x458/0x8d0 net/xfrm/xfrm_user.c:2663
netlink_rcv_skb+0x17d/0x410 net/netlink/af_netlink.c:2477
xfrm_netlink_rcv+0x70/0x90 net/xfrm/xfrm_user.c:2671
netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
netlink_unicast+0x574/0x770 net/netlink/af_netlink.c:1336
netlink_sendmsg+0xa05/0xf90 net/netlink/af_netlink.c:1917
sock_sendmsg_nosec net/socket.c:621 [inline]
sock_sendmsg+0xdd/0x130 net/socket.c:631
___sys_sendmsg+0x7ec/0x910 net/socket.c:2116
__sys_sendmsg+0x112/0x270 net/socket.c:2154
__do_sys_sendmsg net/socket.c:2163 [inline]
__se_sys_sendmsg net/socket.c:2161 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2161
do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457ec9
Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f2e4aef1c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457ec9
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2e4aef26d4
R13: 00000000004c5394 R14: 00000000004d8e30 R15: 00000000ffffffff

Allocated by task 2682:
save_stack+0x45/0xd0 mm/kasan/common.c:73
set_track mm/kasan/common.c:85 [inline]
kasan_kmalloc mm/kasan/common.c:482 [inline]
kasan_kmalloc+0xcf/0xe0 mm/kasan/common.c:455
kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:397
kmem_cache_alloc+0x12d/0x710 mm/slab.c:3541
getname_flags fs/namei.c:140 [inline]
getname_flags+0xd6/0x5b0 fs/namei.c:129
getname+0x1a/0x20 fs/namei.c:211
do_sys_open+0x3a5/0x7c0 fs/open.c:1057
__do_sys_open fs/open.c:1081 [inline]
__se_sys_open fs/open.c:1076 [inline]
__x64_sys_open+0x7e/0xc0 fs/open.c:1076
do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 2682:
save_stack+0x45/0xd0 mm/kasan/common.c:73
set_track mm/kasan/common.c:85 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:444
kasan_slab_free+0xe/0x10 mm/kasan/common.c:452
__cache_free mm/slab.c:3485 [inline]
kmem_cache_free+0x86/0x260 mm/slab.c:3747
putname+0xef/0x130 fs/namei.c:261
do_sys_open+0x3f4/0x7c0 fs/open.c:1072
__do_sys_open fs/open.c:1081 [inline]
__se_sys_open fs/open.c:1076 [inline]
__x64_sys_open+0x7e/0xc0 fs/open.c:1076
do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880a57d0800
which belongs to the cache names_cache of size 4096
The buggy address is located 359 bytes to the left of
4096-byte region [ffff8880a57d0800, ffff8880a57d1800)
The buggy address belongs to the page:
page:ffffea000295f400 count:1 mapcount:0 mapping:ffff88821bc49080 index:0x0
compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea0002949788 ffffea00027c8208 ffff88821bc49080
raw: 0000000000000000 ffff8880a57d0800 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a57d0580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a57d0600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8880a57d0680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff8880a57d0700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a57d0780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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