linux-kernel - Re: [PATCH v2 2/9] mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page

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Date:   Fri, 24 Jun 2022 13:57:57 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Naoya Horiguchi <nao.horiguchi@...il.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Oscar Salvador <osalvador@...e.de>,
        Muchun Song <songmuchun@...edance.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/9] mm/hugetlb: separate path for hwpoison entry in
 copy_hugetlb_page_range()

On 06/24/22 08:51, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@....com>
> 
> Originally copy_hugetlb_page_range() handles migration entries and hwpoisone
> entries in similar manner.  But recently the related code path has more code
> for migration entries, and when is_writable_migration_entry() was converted
> to !is_readable_migration_entry(), hwpoison entries on source processes got
> to be unexpectedly updated (which is legitimate for migration entries, but
> not for hwpoison entries).  This results in unexpected serious issues like
> kernel panic when foking processes with hwpoison entries in pmd.
> 
> Separate the if branch into one for hwpoison entries and one for migration
> entries.
> 
> Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive")
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>
> Cc: <stable@...r.kernel.org> # 5.18
> ---
>  mm/hugetlb.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)

Thank you!

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
(with typos pointed out by Miaohe Lin)

Just curious, are there any hwpoisoned tests in any test suite?  I run
libhugetlbfs tests and ltp on a regular basis which sometimes catch
regressions.  If there are no tests in any suite today, this might be
something we want to consider for future work.

-- 
Mike Kravetz