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

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

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    425c075d Merge branch 'tun-debug'
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=134d2ae3e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=598678fc6e800071
dashboard link: https://syzkaller.appspot.com/bug?extid=c72da7b9ed57cde6fca2
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=122ed70de00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=116689fde00000

The bug was bisected to:

commit 599be01ee567b61f4471ee8078870847d0a11e8e
Author: Cong Wang <xiyou.wangcong@gmail.com>
Date:   Mon Feb 3 05:14:35 2020 +0000

    net_sched: fix an OOB access in cls_tcindex

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=150a7d53e00000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=170a7d53e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=130a7d53e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c72da7b9ed57cde6fca2@syzkaller.appspotmail.com
Fixes: 599be01ee567 ("net_sched: fix an OOB access in cls_tcindex")

IPVS: ftp: loaded support on port[0] = 21
==================================================================
BUG: KASAN: slab-out-of-bounds in tcindex_set_parms+0x17fd/0x1a00 net/sched/cls_tcindex.c:455
Write of size 16 at addr ffff8880a219e6b8 by task syz-executor508/9705

CPU: 1 PID: 9705 Comm: syz-executor508 Not tainted 5.6.0-rc3-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
 tcindex_set_parms+0x17fd/0x1a00 net/sched/cls_tcindex.c:455
 tcindex_change+0x203/0x2e0 net/sched/cls_tcindex.c:518
 tc_new_tfilter+0xa59/0x20b0 net/sched/cls_api.c:2103
 rtnetlink_rcv_msg+0x810/0xad0 net/core/rtnetlink.c:5431
 netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2478
 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:2343
 ___sys_sendmsg+0x100/0x170 net/socket.c:2397
 __sys_sendmsg+0xec/0x1b0 net/socket.c:2430
 do_syscall_64+0xf6/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440eb9
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 7b 10 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffef61bf118 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004a2690 RCX: 0000000000440eb9
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 00000000004a2690 R08: 0000000120080522 R09: 0000000120080522
R10: 0000000120080522 R11: 0000000000000246 R12: 00000000004023c0
R13: 0000000000402450 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 9705:
 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
 kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 tcindex_set_parms+0x1f1/0x1a00 net/sched/cls_tcindex.c:325
 tcindex_change+0x203/0x2e0 net/sched/cls_tcindex.c:518
 tc_new_tfilter+0xa59/0x20b0 net/sched/cls_api.c:2103
 rtnetlink_rcv_msg+0x810/0xad0 net/core/rtnetlink.c:5431
 netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2478
 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:2343
 ___sys_sendmsg+0x100/0x170 net/socket.c:2397
 __sys_sendmsg+0xec/0x1b0 net/socket.c:2430
 do_syscall_64+0xf6/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 2501:
 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
 call_usermodehelper_freeinfo kernel/umh.c:48 [inline]
 umh_complete kernel/umh.c:62 [inline]
 umh_complete+0x81/0x90 kernel/umh.c:51
 call_usermodehelper_exec_async+0x459/0x710 kernel/umh.c:122
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff8880a219e600
 which belongs to the cache kmalloc-192 of size 192
The buggy address is located 184 bytes inside of
 192-byte region [ffff8880a219e600, ffff8880a219e6c0)
The buggy address belongs to the page:
page:ffffea0002886780 refcount:1 mapcount:0 mapping:ffff8880aa000000 index:0xffff8880a219ef00
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002882b88 ffff8880aa001138 ffff8880aa000000
raw: ffff8880a219ef00 ffff8880a219e000 000000010000000b 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a219e580: 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a219e600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880a219e680: 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                        ^
 ffff8880a219e700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a219e780: fb fb fb fb fb fb fb fb 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.
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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

Re: KASAN: slab-out-of-bounds Write in tcindex_set_parms

[Cong Wang]

On Sun, Mar 8, 2020 at 3:44 PM syzbot
<syzbot+c72da7b9ed57cde6fca2@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    425c075d Merge branch 'tun-debug'
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=134d2ae3e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=598678fc6e800071
> dashboard link: https://syzkaller.appspot.com/bug?extid=c72da7b9ed57cde6fca2
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=122ed70de00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=116689fde00000
>
> The bug was bisected to:
>
> commit 599be01ee567b61f4471ee8078870847d0a11e8e
> Author: Cong Wang <xiyou.wangcong@gmail.com>
> Date:   Mon Feb 3 05:14:35 2020 +0000
>
>     net_sched: fix an OOB access in cls_tcindex
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=150a7d53e00000
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=170a7d53e00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=130a7d53e00000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+c72da7b9ed57cde6fca2@syzkaller.appspotmail.com
> Fixes: 599be01ee567 ("net_sched: fix an OOB access in cls_tcindex")
>
> IPVS: ftp: loaded support on port[0] = 21
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in tcindex_set_parms+0x17fd/0x1a00 net/sched/cls_tcindex.c:455
> Write of size 16 at addr ffff8880a219e6b8 by task syz-executor508/9705
>
> CPU: 1 PID: 9705 Comm: syz-executor508 Not tainted 5.6.0-rc3-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
>  tcindex_set_parms+0x17fd/0x1a00 net/sched/cls_tcindex.c:455


I think we probably don't check the boundary of 'handle' properly.

397         if (cp->perfect || valid_perfect_hash(cp))
398                 if (handle >= cp->alloc_hash)
399                         goto errout_alloc;

I will think more about it.

Thanks.

Re: KASAN: slab-out-of-bounds Write in tcindex_set_parms

[Cong Wang]

#syz test: https://github.com/congwang/linux.git tcindex

Re: KASAN: slab-out-of-bounds Write in tcindex_set_parms

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger crash:

Reported-and-tested-by: syzbot+c72da7b9ed57cde6fca2@syzkaller.appspotmail.com

Tested on:

commit:         2c19e526 net_sched: hold rtnl lock for tcindex_partial_des..
git tree:       https://github.com/congwang/linux.git tcindex
kernel config:  https://syzkaller.appspot.com/x/.config?x=bcbe864577669742
dashboard link: https://syzkaller.appspot.com/bug?extid=c72da7b9ed57cde6fca2
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Note: testing is done by a robot and is best-effort only.