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

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Message-ID: <Yrli5c0A8oKqF4EG@FVFYT0MHHV2J.usts.net>
Date:   Mon, 27 Jun 2022 15:57:25 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Naoya Horiguchi <nao.horiguchi@...il.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Oscar Salvador <osalvador@...e.de>,
        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 Fri, Jun 24, 2022 at 08:51:46AM +0900, 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>

Thanks for fixing it.

Reviewed-by: Muchun Song <songmuchun@...edance.com>