KASAN: slab-out-of-bounds Write in xfrm_attr_cpy32

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c4d6fe73 Merge tag 'xarray-5.9' of git://git.infradead.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1117ff78500000
kernel config: https://syzkaller.appspot.com/x/.config?x=5e8379456358b93c
dashboard link: https://syzkaller.appspot.com/bug?extid=c43831072e7df506a646
compiler: gcc (GCC) 10.1.0-syz 20200507
userspace arch: i386

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c43831...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in memset include/linux/string.h:384 [inline]
BUG: KASAN: slab-out-of-bounds in xfrm_attr_cpy32+0x15a/0x1d0 net/xfrm/xfrm_compat.c:393
Write of size 4 at addr ffff88801c57e6c0 by task syz-executor.0/9498

CPU: 1 PID: 9498 Comm: syz-executor.0 Not tainted 5.9.0-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x107/0x163 lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:385
__kasan_report mm/kasan/report.c:545 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
check_memory_region_inline mm/kasan/generic.c:186 [inline]
check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
memset+0x20/0x40 mm/kasan/common.c:84
memset include/linux/string.h:384 [inline]
xfrm_attr_cpy32+0x15a/0x1d0 net/xfrm/xfrm_compat.c:393
xfrm_xlate32_attr net/xfrm/xfrm_compat.c:426 [inline]
xfrm_xlate32 net/xfrm/xfrm_compat.c:525 [inline]
xfrm_user_rcv_msg_compat+0x76b/0x1040 net/xfrm/xfrm_compat.c:570
xfrm_user_rcv_msg+0x55b/0x8b0 net/xfrm/xfrm_user.c:2714
netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2494
xfrm_netlink_rcv+0x6b/0x90 net/xfrm/xfrm_user.c:2764
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:671
____sys_sendmsg+0x6e8/0x810 net/socket.c:2353
___sys_sendmsg+0xf3/0x170 net/socket.c:2407
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2440
do_syscall_32_irqs_on arch/x86/entry/common.c:78 [inline]
__do_fast_syscall_32+0x56/0x80 arch/x86/entry/common.c:137
do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:160
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7f86549
Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f55800bc EFLAGS: 00000296 ORIG_RAX: 0000000000000172
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000200001c0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 9498:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
kmalloc_node include/linux/slab.h:577 [inline]
kvmalloc_node+0x61/0xf0 mm/util.c:575
kvmalloc include/linux/mm.h:765 [inline]
xfrm_user_rcv_msg_compat+0x3cd/0x1040 net/xfrm/xfrm_compat.c:566
xfrm_user_rcv_msg+0x55b/0x8b0 net/xfrm/xfrm_user.c:2714
netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2494
xfrm_netlink_rcv+0x6b/0x90 net/xfrm/xfrm_user.c:2764
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:671
____sys_sendmsg+0x6e8/0x810 net/socket.c:2353
___sys_sendmsg+0xf3/0x170 net/socket.c:2407
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2440
do_syscall_32_irqs_on arch/x86/entry/common.c:78 [inline]
__do_fast_syscall_32+0x56/0x80 arch/x86/entry/common.c:137
do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:160
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

Last call_rcu():
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_record_aux_stack+0x82/0xb0 mm/kasan/generic.c:346
__call_rcu kernel/rcu/tree.c:2953 [inline]
call_rcu+0xbb/0x700 kernel/rcu/tree.c:3027
nf_hook_entries_free net/netfilter/core.c:88 [inline]
nf_hook_entries_free net/netfilter/core.c:75 [inline]
__nf_register_net_hook+0x2aa/0x610 net/netfilter/core.c:424
nf_register_net_hook+0x114/0x170 net/netfilter/core.c:541
nf_register_net_hooks+0x59/0xc0 net/netfilter/core.c:557
ip6t_register_table+0x235/0x2f0 net/ipv6/netfilter/ip6_tables.c:1757
ip6table_security_table_init net/ipv6/netfilter/ip6table_security.c:58 [inline]
ip6table_security_table_init+0x82/0xc0 net/ipv6/netfilter/ip6table_security.c:47
xt_find_table_lock+0x2d4/0x540 net/netfilter/x_tables.c:1223
xt_request_find_table_lock+0x27/0xf0 net/netfilter/x_tables.c:1253
get_info+0x16a/0x740 net/ipv6/netfilter/ip6_tables.c:980
do_ip6t_get_ctl+0x152/0xa10 net/ipv6/netfilter/ip6_tables.c:1660
nf_getsockopt+0x72/0xd0 net/netfilter/nf_sockopt.c:116
ipv6_getsockopt+0x1be/0x270 net/ipv6/ipv6_sockglue.c:1486
tcp_getsockopt+0x86/0xd0 net/ipv4/tcp.c:3880
__sys_getsockopt+0x219/0x4c0 net/socket.c:2173
__do_compat_sys_socketcall+0x513/0x660 net/compat.c:495
do_syscall_32_irqs_on arch/x86/entry/common.c:78 [inline]
__do_fast_syscall_32+0x56/0x80 arch/x86/entry/common.c:137
do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:160
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

The buggy address belongs to the object at ffff88801c57e600
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 0 bytes to the right of
192-byte region [ffff88801c57e600, ffff88801c57e6c0)
The buggy address belongs to the page:
page:00000000d5f129f9 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88801c57eb00 pfn:0x1c57e
flags: 0xfff00000000200(slab)
raw: 00fff00000000200 ffff888010041140 ffffea00008066c8 ffff888010040000
raw: ffff88801c57eb00 ffff88801c57e000 000000010000000b 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88801c57e580: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
ffff88801c57e600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88801c57e680: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
^
ffff88801c57e700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88801c57e780: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================


---
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[Hillf Danton]

On Fri, 23 Oct 2020 01:38:23 -0700

Check bound after updating pos and before clearing memory.

--- a/net/xfrm/xfrm_compat.c
+++ b/net/xfrm/xfrm_compat.c
@@ -376,6 +376,7 @@ static int xfrm_attr_cpy32(void *dst, si
{
struct nlmsghdr *nlmsg = dst;
struct nlattr *nla;
+ int len;

if (WARN_ON_ONCE(copy_len > payload))
copy_len = payload;
@@ -390,7 +391,10 @@ static int xfrm_attr_cpy32(void *dst, si
*pos += nla_attr_size(payload);
nlmsg->nlmsg_len += nla->nla_len;

- memset(dst + *pos, 0, payload - copy_len);
+ len = payload - copy_len;
+ if (size - *pos < len)
+ len = size - *pos;
+ memset(dst + *pos, 0, len);
*pos += payload - copy_len;

return 0;

[Steffen Klassert]

Dimitry, you added this code, can you please look into
that?

Thanks!

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 3cea11cd Linux 5.10-rc2
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16baaf46500000
kernel config: https://syzkaller.appspot.com/x/.config?x=61033507391c77ff

dashboard link: https://syzkaller.appspot.com/bug?extid=c43831072e7df506a646
compiler: gcc (GCC) 10.1.0-syz 20200507
userspace arch: i386

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1388676c500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=158f642c500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c43831...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in memset include/linux/string.h:384 [inline]
BUG: KASAN: slab-out-of-bounds in xfrm_attr_cpy32+0x15a/0x1d0 net/xfrm/xfrm_compat.c:393

Write of size 4 at addr ffff888147aba4fc by task syz-executor829/8497

CPU: 0 PID: 8497 Comm: syz-executor829 Not tainted 5.10.0-rc2-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+0x107/0x163 lib/dump_stack.c:118

print_address_description.constprop.0.cold+0xae/0x4c8 mm/kasan/report.c:385

RIP: 0023:0xf7fb2549
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000ffdebbcc EFLAGS: 00000246 ORIG_RAX: 0000000000000172
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000020000080
RDX: 0000000000000000 RSI: 00000000080ea078 RDI: 00000000ffdebc20

RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 8497:

kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]

__kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:461
kmalloc_node include/linux/slab.h:575 [inline]

kvmalloc_node+0x61/0xf0 mm/util.c:575
kvmalloc include/linux/mm.h:765 [inline]
xfrm_user_rcv_msg_compat+0x3cd/0x1040 net/xfrm/xfrm_compat.c:566
xfrm_user_rcv_msg+0x55b/0x8b0 net/xfrm/xfrm_user.c:2714
netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2494
xfrm_netlink_rcv+0x6b/0x90 net/xfrm/xfrm_user.c:2764
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:671
____sys_sendmsg+0x6e8/0x810 net/socket.c:2353
___sys_sendmsg+0xf3/0x170 net/socket.c:2407
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2440
do_syscall_32_irqs_on arch/x86/entry/common.c:78 [inline]
__do_fast_syscall_32+0x56/0x80 arch/x86/entry/common.c:137
do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:160
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

Last call_rcu():
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48

kasan_record_aux_stack+0xc0/0xf0 mm/kasan/generic.c:346

__call_rcu kernel/rcu/tree.c:2953 [inline]
call_rcu+0xbb/0x700 kernel/rcu/tree.c:3027

rhashtable_rehash_table lib/rhashtable.c:345 [inline]
rht_deferred_worker+0x10f4/0x1d40 lib/rhashtable.c:429
process_one_work+0x933/0x15a0 kernel/workqueue.c:2272
worker_thread+0x64c/0x1120 kernel/workqueue.c:2418
kthread+0x3af/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

The buggy address belongs to the object at ffff888147aba400
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 252 bytes inside of
256-byte region [ffff888147aba400, ffff888147aba500)

The buggy address belongs to the page:

page:00000000e11e2d62 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888147abbe00 pfn:0x147aba
head:00000000e11e2d62 order:1 compound_mapcount:0
flags: 0x57ff00000010200(slab|head)
raw: 057ff00000010200 ffffea000084e900 0000000700000007 ffff8880100413c0
raw: ffff888147abbe00 000000008010000f 00000001ffffffff 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff888147aba380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888147aba400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888147aba480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 04
^
ffff888147aba500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888147aba580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

[syzbot]

syzbot has bisected this issue to:

commit 5106f4a8acff480e244300bc5097c0ad7048c3a2
Author: Dmitry Safonov <di...@arista.com>
Date: Mon Sep 21 14:36:55 2020 +0000

xfrm/compat: Add 32=>64-bit messages translator

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=16cefa8a500000
start commit: 3cea11cd Linux 5.10-rc2
git tree: upstream
final oops: https://syzkaller.appspot.com/x/report.txt?x=15cefa8a500000
console output: https://syzkaller.appspot.com/x/log.txt?x=11cefa8a500000

kernel config: https://syzkaller.appspot.com/x/.config?x=61033507391c77ff
dashboard link: https://syzkaller.appspot.com/bug?extid=c43831072e7df506a646

userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1388676c500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=158f642c500000

Reported-by: syzbot+c43831...@syzkaller.appspotmail.com
Fixes: 5106f4a8acff ("xfrm/compat: Add 32=>64-bit messages translator")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection