Date:   Mon, 15 Nov 2021 13:16:33 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Bui Quang Minh <minhquangbui99@gmail.com>
Cc:     Mike Kravetz <mike.kravetz@oracle.com>,
        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
Subject: Re: [PATCH] hugetlb: fix hugetlb cgroup refcounting during mremap
Message-Id: <20211115131633.81e1879e36aed4a0290e6f0c@linux-foundation.org>
In-Reply-To: <20211113154412.91134-1-minhquangbui99@gmail.com>
References: <20211113154412.91134-1-minhquangbui99@gmail.com>
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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()

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.