Re: [PATCH] mm/hugetlb: Fix use after free when subpool max_hpages accounting is not enabled

[Miaohe Lin]

Hi:
On 2021/1/28 8:17, Andrew Morton wrote:
> On Wed, 27 Jan 2021 10:08:22 +0800 Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote:
> 
>> On 2021/1/27 8:06, Mike Kravetz wrote:
>>> On 1/26/21 3:55 AM, Miaohe Lin wrote:
>>>> When subpool max_hpages accounting is not enabled, used_hpages is always 0
>>>> and might lead to release subpool prematurely because it indicates no pages
>>>> are used now while there might be.
>>>
>>> It might be good to say that you need min_hpages accounting (min_size mount
>>> option) enabled for this issue to occur.  Or, perhaps say this is possible
>>> if a hugetlbfs filesystem is created with the min_size option and without
>>> the size option.
>>>
>>> That might better explain the conditions in which a user could see the issue.
>>
>> So commit log might looks like this ?
>> """
>> If a hugetlbfs filesystem is created with the min_size option and without
>> the size option, used_hpages is always 0 and might lead to release subpool
>> prematurely because it indicates no pages are used now while there might
>> be.
>>
>> In order to fix this issue, we should check used_hpages == 0 iff max_hpages
>> accounting is enabled. As max_hpages accounting should be enabled in most
>> common case, this is not worth a Cc stable.
>> """
>>
>> If so, should I send a V2 or Andrew would kindly do this?
>> Many thanks.
> 
> I made that change, thanks.>

It's very kind of you. Many thanks.:)

> .
>