KASAN: use-after-free Read in tipc_group_cong

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: f5d582777bcb Merge branch 'for-linus' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1705d525400000
kernel config: https://syzkaller.appspot.com/x/.config?x=c8970c89a0efbb23
dashboard link: https://syzkaller.appspot.com/bug?extid=9845fed98688e01f431e
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=101b6ba3400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9845fe...@syzkaller.appspotmail.com

8021q: adding VLAN 0 to HW filter on device team0
8021q: adding VLAN 0 to HW filter on device team0
audit: type=1400 audit(1544592509.246:38): avc: denied { associate } for
pid=6204 comm="syz-executor5" name="syz5"
scontext=unconfined_u:object_r:unlabeled_t:s0
tcontext=system_u:object_r:unlabeled_t:s0 tclass=filesystem permissive=1
==================================================================
BUG: KASAN: use-after-free in tipc_group_find_dest net/tipc/group.c:255
[inline]
BUG: KASAN: use-after-free in tipc_group_cong+0x566/0x5d0
net/tipc/group.c:416
Read of size 8 at addr ffff8881c59f5000 by task syz-executor4/10565

CPU: 1 PID: 10565 Comm: syz-executor4 Not tainted 4.20.0-rc6+ #151
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+0x244/0x39d lib/dump_stack.c:113
print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
tipc_group_find_dest net/tipc/group.c:255 [inline]
tipc_group_cong+0x566/0x5d0 net/tipc/group.c:416
tipc_send_group_anycast+0x9bb/0xc80 net/tipc/socket.c:972
__tipc_sendmsg+0x12b1/0x1d40 net/tipc/socket.c:1309
tipc_sendmsg+0x50/0x70 net/tipc/socket.c:1272
sock_sendmsg_nosec net/socket.c:621 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:631
___sys_sendmsg+0x7fd/0x930 net/socket.c:2116
__sys_sendmsg+0x11d/0x280 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+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457679
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f813d748c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457679
RDX: 0000000000000000 RSI: 00000000200006c0 RDI: 0000000000000005
RBP: 000000000072bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f813d7496d4
R13: 00000000004c44dd R14: 00000000004d74c8 R15: 00000000ffffffff

Allocated by task 10551:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
kmalloc include/linux/slab.h:546 [inline]
kzalloc include/linux/slab.h:741 [inline]
tipc_group_create+0x152/0xa70 net/tipc/group.c:171
tipc_sk_join net/tipc/socket.c:2829 [inline]
tipc_setsockopt+0x2d1/0xd70 net/tipc/socket.c:2944
__sys_setsockopt+0x1ba/0x3c0 net/socket.c:1902
__do_sys_setsockopt net/socket.c:1913 [inline]
__se_sys_setsockopt net/socket.c:1910 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:1910
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 10567:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3817
tipc_group_delete+0x2e4/0x3f0 net/tipc/group.c:227
tipc_sk_leave+0x113/0x220 net/tipc/socket.c:2863
tipc_setsockopt+0x97d/0xd70 net/tipc/socket.c:2947
__sys_setsockopt+0x1ba/0x3c0 net/socket.c:1902
__do_sys_setsockopt net/socket.c:1913 [inline]
__se_sys_setsockopt net/socket.c:1910 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:1910
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881c59f5000
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 0 bytes inside of
192-byte region [ffff8881c59f5000, ffff8881c59f50c0)
The buggy address belongs to the page:
page:ffffea0007167d40 count:1 mapcount:0 mapping:ffff8881da800040 index:0x0
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffffea0007160488 ffffea00071aff08 ffff8881da800040
raw: 0000000000000000 ffff8881c59f5000 0000000100000010 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881c59f4f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881c59f4f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8881c59f5000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881c59f5080: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8881c59f5100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
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[Jon Maloy]

> -----Original Message-----
> From: syzbot <syzbot+9845fe...@syzkaller.appspotmail.com>
> Sent: 12-Dec-18 06:11
> To: da...@davemloft.net; Jon Maloy <jon....@ericsson.com>; linux-
> ker...@vger.kernel.org; net...@vger.kernel.org; syzkaller-
> bu...@googlegroups.com; tipc-di...@lists.sourceforge.net;
> ying...@windriver.com
> Subject: KASAN: use-after-free Read in tipc_group_cong

This seems to be an effect of the same bug as reported in
https://syzkaller.appspot.com/bug?extid=10a9db47c3a0e13eb31c

Cong posted a fix for that one. Did you see the crash after applying his patch?

///jon

[Dmitry Vyukov]

On Thu, Dec 13, 2018 at 1:16 AM Jon Maloy <jon....@ericsson.com> wrote:
> > -----Original Message-----
> > From: syzbot <syzbot+9845fe...@syzkaller.appspotmail.com>
> > Sent: 12-Dec-18 06:11
> > To: da...@davemloft.net; Jon Maloy <jon....@ericsson.com>; linux-
> > ker...@vger.kernel.org; net...@vger.kernel.org; syzkaller-
> > bu...@googlegroups.com; tipc-di...@lists.sourceforge.net;
> > ying...@windriver.com
> > Subject: KASAN: use-after-free Read in tipc_group_cong
>
> This seems to be an effect of the same bug as reported in
> https://syzkaller.appspot.com/bug?extid=10a9db47c3a0e13eb31c

Let's do

#syz dup: KASAN: use-after-free Read in tipc_group_bc_cong

then.

> Cong posted a fix for that one. Did you see the crash after applying his patch?

Which patch do you mean? Unfortunately kernel development process is
so that it's not possible to figure out what fixes what.

I would just wait for new syzbot results.

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[Jon Maloy]

This one:
[Patch net] tipc: check tsk->group in tipc_wait_for_cond()

///jon

[Dmitry Vyukov]

I see it includes syzbot Reported-by tag for "KASAN: use-after-free
Read in tipc_group_bc_cong". So we just wait for syzbot reaction now.

> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/DM5PR15MB1513DB1A65401CB9C924D2B39AA00%40DM5PR15MB1513.namprd15.prod.outlook.com.