linux-kernel - Re: [PATCH v4 4/5] mm: Fix page reference leak in soft_offline

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Message-ID: <CAPcyv4jGXoMA2=OGa42_SuOiPjHUH2o_1YE5jQxU51PyKn6b2w@mail.gmail.com>
Date:   Sun, 17 Jan 2021 14:35:36 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Naoya Horiguchi <nao.horiguchi@...il.com>,
        Michal Hocko <mhocko@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Oscar Salvador <osalvador@...e.de>,
        stable <stable@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 4/5] mm: Fix page reference leak in soft_offline_page()

On Sun, Jan 17, 2021 at 2:01 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Wed, 13 Jan 2021 16:43:32 -0800 Dan Williams <dan.j.williams@...el.com> wrote:
>
> > The conversion to move pfn_to_online_page() internal to
> > soft_offline_page() missed that the get_user_pages() reference taken by
> > the madvise() path needs to be dropped when pfn_to_online_page() fails.
> > Note the direct sysfs-path to soft_offline_page() does not perform a
> > get_user_pages() lookup.
> >
> > When soft_offline_page() is handed a pfn_valid() &&
> > !pfn_to_online_page() pfn the kernel hangs at dax-device shutdown due to
> > a leaked reference.
> >
> > Fixes: feec24a6139d ("mm, soft-offline: convert parameter to pfn")
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Naoya Horiguchi <nao.horiguchi@...il.com>
> > Cc: Michal Hocko <mhocko@...nel.org>
> > Reviewed-by: David Hildenbrand <david@...hat.com>
> > Reviewed-by: Oscar Salvador <osalvador@...e.de>
> > Cc: <stable@...r.kernel.org>
> > Signed-off-by: Dan Williams <dan.j.williams@...el.com>
>
> A cc:stable patch in the middle is awkward.  I'll make this a
> standalone patch for merging into mainline soon (for 5.11) and shall
> turn the rest into a 4-patch series, OK?

Sounds good to me.