Subject: Re: [PATCH] hugetlb: fix hugetlb cgroup refcounting during mremap
To:     Andrew Morton <akpm@linux-foundation.org>,
        Bui Quang Minh <minhquangbui99@gmail.com>
Cc:     Miaohe Lin <linmiaohe@huawei.com>, Michal Hocko <mhocko@suse.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Mina Almasry <almasrymina@google.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
References: <20211113154412.91134-1-minhquangbui99@gmail.com>
 <20211115131633.81e1879e36aed4a0290e6f0c@linux-foundation.org>
From:   Mike Kravetz <mike.kravetz@oracle.com>
Message-ID: <a2b26f56-de7a-2192-f6b3-bf80d598f725@oracle.com>
Date:   Mon, 15 Nov 2021 15:25:23 -0800
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Subject:   Re: [PATCH] hugetlb: fix hugetlb cgroup refcounting during mremap

To:        Andrew Morton <akpm@linux-foundation.org>, Bui Quang Minh <minhquangbui99@gmail.com>

Cc:        Miaohe Lin <linmiaohe@huawei.com>, Michal Hocko <mhocko@suse.com>, Muchun Song <songmuchun@bytedance.com>, Mina Almasry <almasrymina@google.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org

Bcc:       

-=-=-=-=-=-=-=-=-=# Don't remove this line #=-=-=-=-=-=-=-=-=-

On 11/15/21 1:16 PM, Andrew Morton wrote:

> On Sat, 13 Nov 2021 22:44:10 +0700 Bui Quang Minh <minhquangbui99@gmail.com> wrote:

> 

>> When hugetlb_vm_op_open() is called during copy_vma(), we may take the

>> reference to resv_map->css. Later, when clearing the reservation pointer

>> of old_vma after transferring it to new_vma, we forget to drop the

>> reference to resv_map->css. This leads to a reference leak of css.

>>

>> Fixes this by adding a check to drop reservation css  reference in

>> clear_vma_resv_huge_pages()


Good catch!  Sorry I missed this in my review.


Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com


> Thanks.  I added cc:stable to this (550a7d60bd5e35a was merged a year

> ago) and I've queued it for 5.16-rc2, pending suitable reviewer feedback.


I may be confused, but 550a7d60bd5e35a was just merged in 5.16-rc1 so

no need for cc:stable.

-- 

Mike Kravetz