linux-kernel - Re: [PATCH] hugetlb: fix hugetlb cgroup refcounting during mremap

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Message-ID: <CAHS8izOogXwHAcrvL6HtXFh56EbD+mUJ6cAaq4ADqtQngKEzZQ@mail.gmail.com>
Date:   Mon, 15 Nov 2021 14:39:08 -0800
From:   Mina Almasry <almasrymina@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Bui Quang Minh <minhquangbui99@...il.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Michal Hocko <mhocko@...e.com>,
        Muchun Song <songmuchun@...edance.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] hugetlb: fix hugetlb cgroup refcounting during mremap

On Mon, Nov 15, 2021 at 1:16 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Sat, 13 Nov 2021 22:44:10 +0700 Bui Quang Minh <minhquangbui99@...il.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.
>

Thanks,

Reviewed-by: Mina Almasry <almasrymina@...gle.com>