Re: KASAN: use-after-free Read in get_work_pool

[Dmitry Vyukov]

On Wed, Dec 6, 2017 at 1:50 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
> On Fri, Oct 27, 2017 at 11:18 PM, Cong Wang <xiyou.wangcong@xxxxxxxxx> wrote:
>> On Thu, Oct 26, 2017 at 11:00 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
>>> On Thu, Oct 26, 2017 at 7:58 PM, Tejun Heo <tj@xxxxxxxxxx> wrote:
>>>> Hello,
>>>>
>>>> On Thu, Oct 26, 2017 at 09:35:44AM -0700, syzbot wrote:
>>>>> BUG: KASAN: use-after-free in __read_once_size
>>>>> include/linux/compiler.h:276 [inline]
>>>>> BUG: KASAN: use-after-free in atomic64_read
>>>>> arch/x86/include/asm/atomic64_64.h:21 [inline]
>>>>> BUG: KASAN: use-after-free in atomic_long_read
>>>>> include/asm-generic/atomic-long.h:44 [inline]
>>>>> BUG: KASAN: use-after-free in get_work_pool+0x1c2/0x1e0
>>>>> kernel/workqueue.c:709
>>>>> Read of size 8 at addr ffff8801cc58c378 by task syz-executor5/21326
>>>>>
>>>>> CPU: 1 PID: 21326 Comm: syz-executor5 Not tainted 4.13.0+ #43
>>>>> Hardware name: Google Google Compute Engine/Google Compute Engine,
>>>>> BIOS Google 01/01/2011
>>>>> Call Trace:
>>>>>  __dump_stack lib/dump_stack.c:16 [inline]
>>>>>  dump_stack+0x194/0x257 lib/dump_stack.c:52
>>>>>  print_address_description+0x73/0x250 mm/kasan/report.c:252
>>>>>  kasan_report_error mm/kasan/report.c:351 [inline]
>>>>>  kasan_report+0x24e/0x340 mm/kasan/report.c:409
>>>>>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
>>>>>  __read_once_size include/linux/compiler.h:276 [inline]
>>>>>  atomic64_read arch/x86/include/asm/atomic64_64.h:21 [inline]
>>>>>  atomic_long_read include/asm-generic/atomic-long.h:44 [inline]
>>>>>  get_work_pool+0x1c2/0x1e0 kernel/workqueue.c:709
>>>>>  __queue_work+0x235/0x1150 kernel/workqueue.c:1401
>>>>>  queue_work_on+0x16a/0x1c0 kernel/workqueue.c:1486
>>>>>  queue_work include/linux/workqueue.h:489 [inline]
>>>>>  strp_check_rcv+0x25/0x30 net/strparser/strparser.c:553
>>>>>  kcm_attach net/kcm/kcmsock.c:1439 [inline]
>>>>>  kcm_attach_ioctl net/kcm/kcmsock.c:1460 [inline]
>>>>>  kcm_ioctl+0x826/0x1610 net/kcm/kcmsock.c:1695
>>>>>  sock_do_ioctl+0x65/0xb0 net/socket.c:961
>>>>>  sock_ioctl+0x2c2/0x440 net/socket.c:1058
>>>>>  vfs_ioctl fs/ioctl.c:45 [inline]
>>>>>  do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:685
>>>>>  SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
>>>>>  entry_SYSCALL_64_fastpath+0x1f/0xbe
>>>>
>>>> Looks like kcm is trying to reuse a work item whose last workqueue has
>>>> been destroyed without re-initing it.  A work item needs to be
>>>> reinit'd.
>>>
>>> +kcm maintainers
>>
>> Can you try the fix below? There is no C reproducer so I can't verify it.
>
>
> Hi Cong,
>
> syzbot can now test proposed patches, see
> https://github.com/google/syzkaller/blob/master/docs/syzbot.md#communication-with-syzbot
> for details. Please give it a try.
>
>> diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
>> index af4e76ac88ff..7816f44c576a 100644
>> --- a/net/kcm/kcmsock.c
>> +++ b/net/kcm/kcmsock.c
>> @@ -1433,11 +1433,12 @@ static int kcm_attach(struct socket *sock,
>> struct socket *csock,
>>         KCM_STATS_INCR(mux->stats.psock_attach);
>>         mux->psocks_cnt++;
>>         psock_now_avail(psock);
>> -       spin_unlock_bh(&mux->lock);
>>
>>         /* Schedule RX work in case there are already bytes queued */
>>         strp_check_rcv(&psock->strp);
>>
>> +       spin_unlock_bh(&mux->lock);
>> +
>>         return 0;
>>  }


Hi Cong,

Was this ever merged? Is it still necessary?