PING: RFR: 8236489: Java heap file on daxfs should be more secure

[Yasumasa Suenaga]

Thanks Ioi!

Yasumasa

On 2020/01/03 11:37, Ioi Lam wrote:
> HI Yasumasa , the change look OK to me.
> 
> Thanks
> - Ioi
> 
> On 1/2/20 5:53 PM, Yasumasa Suenaga wrote:
>> PING: Could you review it?
>>
>>>    JBS: https://bugs.openjdk.java.net/browse/JDK-8236489
>>>    webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8236489/webrev.00/
>>
>>
>> Yasumasa
>>
>>
>> On 2019/12/26 11:50, Yasumasa Suenaga wrote:
>>> Hi all,
>>>
>>> I filed this to JBS. Could you review?
>>>
>>>    JBS: https://bugs.openjdk.java.net/browse/JDK-8236489
>>>    webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8236489/webrev.00/
>>>
>>> It has passed all tests on submit repo. (mach5-one-ysuenaga-JDK-8236489-20191226-0145-7795073)
>>>
>>>
>>> Thanks,
>>>
>>> Yasumasa
>>>
>>>
>>> On 2019/12/19 14:58, Yasumasa Suenaga wrote:
>>>> Hi all,
>>>>
>>>> HotSpot allocates Java heap on daxfs if we pass -XX:AllocateHeapAt.
>>>> It performs open(2) and unlink(2) on daxfs, and it is used via mmap'ed address.
>>>>
>>>> mmap(2) would be called with MAP_SHARED, and it is not atomically between open(2) and unlink(2). If malicious user open Java heap file before unlink(2), it might be exposed.
>>>>
>>>> So I think we can use open(2) with O_TMPFILE instead of mkstemp(3) as below.
>>>>
>>>>    http://cr.openjdk.java.net/~ysuenaga/dax/
>>>>
>>>> O_TMPFILE would create inode on filesystem, and it cannot be accessed from out-of-process.
>>>> However it cannot be provided in older Linux kernel. So I keep current code as fall back.
>>>>
>>>>    http://man7.org/linux/man-pages/man2/open.2.html
>>>>
>>>> What do you think about it? or someone is working for it?
>>>> If it is ok, I will file it to JBS and will send review request.
>>>>
>>>>
>>>> Thanks,
>>>>
>>>> Yasumasa
>>>>
>>>>
>>>> P.S.
>>>>    I tried to use MAP_PRIVATE for it, but it was slower than MAP_SHARED.
>