KASAN: use-after-free Read in tipc_group_is_open

[syzbot]

Hello,

syzkaller hit the following crash on
594831a8aba3fd045c3212a3e3bb9788c77b989d
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


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Reported-by: syzbot+799daf...@syzkaller.appspotmail.com
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==================================================================
BUG: KASAN: use-after-free in tipc_group_is_open+0x3a/0x40
net/tipc/group.c:106
Read of size 1 at addr ffff8801d89f7378 by task syzkaller275009/3704

CPU: 0 PID: 3704 Comm: syzkaller275009 Not tainted 4.15.0-rc7+ #190
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_address_description+0x73/0x250 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report+0x25b/0x340 mm/kasan/report.c:409
__asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:427
tipc_group_is_open+0x3a/0x40 net/tipc/group.c:106
tipc_poll+0x364/0x4d0 net/tipc/socket.c:740
sock_poll+0x141/0x320 net/socket.c:1111
do_pollfd fs/select.c:822 [inline]
do_poll fs/select.c:872 [inline]
do_sys_poll+0x715/0x10b0 fs/select.c:966
SYSC_poll fs/select.c:1024 [inline]
SyS_poll+0x10d/0x450 fs/select.c:1012
entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x446129
RSP: 002b:00007f0f2df96db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000007
RAX: ffffffffffffffda RBX: 00000000006dbc54 RCX: 0000000000446129
RDX: 0000000000007fff RSI: 000000000000000a RDI: 0000000020ef5000
RBP: 00000000006dbc50 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc07e2923f R14: 00007f0f2df979c0 R15: 0000000000000007

Allocated by task 3702:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610
kmalloc include/linux/slab.h:499 [inline]
kzalloc include/linux/slab.h:688 [inline]
tipc_group_create+0x144/0x900 net/tipc/group.c:180
tipc_sk_join net/tipc/socket.c:2762 [inline]
tipc_setsockopt+0x274/0xce0 net/tipc/socket.c:2877
SYSC_setsockopt net/socket.c:1823 [inline]
SyS_setsockopt+0x189/0x360 net/socket.c:1802
entry_SYSCALL_64_fastpath+0x23/0x9a

Freed by task 3702:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3488 [inline]
kfree+0xd6/0x260 mm/slab.c:3803
tipc_group_delete+0x2c8/0x3d0 net/tipc/group.c:234
tipc_sk_join net/tipc/socket.c:2775 [inline]
tipc_setsockopt+0xaa9/0xce0 net/tipc/socket.c:2877
SYSC_setsockopt net/socket.c:1823 [inline]
SyS_setsockopt+0x189/0x360 net/socket.c:1802
entry_SYSCALL_64_fastpath+0x23/0x9a

The buggy address belongs to the object at ffff8801d89f7300
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 120 bytes inside of
128-byte region [ffff8801d89f7300, ffff8801d89f7380)
The buggy address belongs to the page:
page:ffffea0007627dc0 count:1 mapcount:0 mapping:ffff8801d89f7000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d89f7000 0000000000000000 0000000100000015
raw: ffffea0007622720 ffffea0007627ce0 ffff8801dac00640 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801d89f7200: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
ffff8801d89f7280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ffff8801d89f7300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801d89f7380: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
ffff8801d89f7400: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
==================================================================


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[Cong Wang]

commit eb929a91b213d2a72c5a8b4af9a1acf63bfb8287
Author: Jon Maloy <jon....@ericsson.com>
Date: Mon Jan 8 21:03:31 2018 +0100

tipc: improve poll() for group member socket

Apparently Jon's commit doesn't fix this. I also don't understand why
Jon believes sock_poll_wait() could sync with setsockopt path...

[Jon Maloy]

While sock_poll_wait() is sleeping, it is possible that the item the 'grp' stack variable is pointing to might be deleted, invalidating the pointer.
This is why I moved the initialization of the pointer to after sock_poll_wait().
However, now tipc_sock->group is clearly set to NULL at both locations where a group item might be deleted, so the reason for the warning must be something else.
I am open to suggestions.

///jon

[Dmitry Vyukov]

FWIW it seems that malloc/free happened within the same syscall when
tipc_sk_publish() in tipc_sk_join() failed. Yet another thread somehow
referenced that object. Was it ever published?

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[Cong Wang]

This doesn't matter at all as long as it doesn't sync setsockopt() path.

> However, now tipc_sock->group is clearly set to NULL at both locations where a group item might be deleted, so the reason for the warning must be something else.
> I am open to suggestions.

Another thread calling tipc_sk_join() could jump in at any time
since we don't have the sock locked here. This is why I said
we probably need to lock the sock here, unless of course
you can refactor the logic to make tipc_poll() not to touch
tsk->group.

[Jon Maloy]

I prefer the latter option. I'll send a patch.

///jon