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

From: syzbot
Date: Mon Mar 30 2020 - 12:41:16 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 906c4043 Merge branch 'i2c/for-current' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14f4a825e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=27392dd2975fd692
dashboard link: https://syzkaller.appspot.com/bug?extid=9bc8c4f42b3e1d0274fe
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1160f46de00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=107c7c97e00000

Bisection is inconclusive: the bug happens on the oldest tested release.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=133ca825e00000
final crash: https://syzkaller.appspot.com/x/report.txt?x=10bca825e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=173ca825e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9bc8c4f42b3e1d0274fe@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:381 [inline]
BUG: KASAN: slab-out-of-bounds in selinux_xfrm_alloc_user+0x23e/0x450 security/selinux/xfrm.c:99
Read of size 768 at addr ffff88808d161934 by task syz-executor391/7036

CPU: 0 PID: 7036 Comm: syz-executor391 Not tainted 5.6.0-rc7-syzkaller #0
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+0x188/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd3/0x315 mm/kasan/report.c:374
__kasan_report.cold+0x1a/0x32 mm/kasan/report.c:506
kasan_report+0xe/0x20 mm/kasan/common.c:641
check_memory_region_inline mm/kasan/generic.c:185 [inline]
check_memory_region+0x128/0x190 mm/kasan/generic.c:192
memcpy+0x20/0x50 mm/kasan/common.c:127
memcpy include/linux/string.h:381 [inline]
selinux_xfrm_alloc_user+0x23e/0x450 security/selinux/xfrm.c:99
security_xfrm_policy_alloc+0x6c/0xb0 security/security.c:2263
copy_from_user_sec_ctx net/xfrm/xfrm_user.c:1462 [inline]
xfrm_policy_construct+0x2a8/0x660 net/xfrm/xfrm_user.c:1627
xfrm_add_acquire+0x215/0x9f0 net/xfrm/xfrm_user.c:2280
xfrm_user_rcv_msg+0x414/0x700 net/xfrm/xfrm_user.c:2676
netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2469
xfrm_netlink_rcv+0x6b/0x90 net/xfrm/xfrm_user.c:2684
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6b9/0x7d0 net/socket.c:2345
___sys_sendmsg+0x100/0x170 net/socket.c:2399
__sys_sendmsg+0xec/0x1b0 net/socket.c:2432
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4405f9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffabe06278 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004405f9
RDX: 0000000000000000 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401e80
R13: 0000000000401f10 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 7036:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc mm/kasan/common.c:515 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:488
__kmalloc_reserve.isra.0+0x39/0xe0 net/core/skbuff.c:142
__alloc_skb+0xef/0x5a0 net/core/skbuff.c:210
alloc_skb include/linux/skbuff.h:1083 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1175 [inline]
netlink_sendmsg+0x97b/0xe10 net/netlink/af_netlink.c:1893
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6b9/0x7d0 net/socket.c:2345
___sys_sendmsg+0x100/0x170 net/socket.c:2399
__sys_sendmsg+0xec/0x1b0 net/socket.c:2432
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 5010:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
kasan_set_free_info mm/kasan/common.c:337 [inline]
__kasan_slab_free+0xf7/0x140 mm/kasan/common.c:476
__cache_free mm/slab.c:3426 [inline]
kfree+0x109/0x2b0 mm/slab.c:3757
skb_free_head+0x8b/0xa0 net/core/skbuff.c:590
skb_release_data+0x42e/0x8b0 net/core/skbuff.c:610
skb_release_all+0x46/0x60 net/core/skbuff.c:664
__kfree_skb net/core/skbuff.c:678 [inline]
consume_skb net/core/skbuff.c:837 [inline]
consume_skb+0xf3/0x400 net/core/skbuff.c:831
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x53f/0x740 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6b9/0x7d0 net/socket.c:2345
___sys_sendmsg+0x100/0x170 net/socket.c:2399
__sys_sendmsg+0xec/0x1b0 net/socket.c:2432
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808d161800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 308 bytes inside of
1024-byte region [ffff88808d161800, ffff88808d161c00)
The buggy address belongs to the page:
page:ffffea0002345840 refcount:1 mapcount:0 mapping:ffff8880aa000c40 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00023d3008 ffffea00029cb048 ffff8880aa000c40
raw: 0000000000000000 ffff88808d161000 0000000100000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88808d161b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88808d161b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88808d161c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff88808d161c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88808d161d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

Next message: Paul Cercueil: "Re: [PATCH v4 3/4] pwm: jz4740: Obtain regmap from parent node"
Previous message: Adam Thomson: "RE: [PATCH 2/3] watchdog: da9063: Use pre configured timeout when watchdog is running"
Next in thread: Yuehaibing: "Re: KASAN: slab-out-of-bounds Read in selinux_xfrm_alloc_user"
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