Re: [PATCH v2 2/9] mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page_range()

From: Mike Kravetz <mike.kravetz@oracle.com>
To: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@redhat.com>,
	Miaohe Lin <linmiaohe@huawei.com>,
	Liu Shixin <liushixin2@huawei.com>,
	Yang Shi <shy828301@gmail.com>,
	Oscar Salvador <osalvador@suse.de>,
	Muchun Song <songmuchun@bytedance.com>,
	Naoya Horiguchi <naoya.horiguchi@nec.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/9] mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page_range()
Date: Fri, 24 Jun 2022 13:57:57 -0700	[thread overview]
Message-ID: <YrYlVdXV+TFLDAGs@monkey> (raw)
In-Reply-To: <20220623235153.2623702-3-naoya.horiguchi@linux.dev>

On 06/24/22 08:51, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@nec.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@nec.com>
> Cc: <stable@vger.kernel.org> # 5.18
> ---
>  mm/hugetlb.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)

Thank you!

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