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Subject: Re: [PATCH] mm: hugetlb_vmemmap: fix a race between vmemmap pmd split
From:   Muchun Song <muchun.song@linux.dev>
In-Reply-To: <20230707123844.adf56ba3e0d000f6da431494@linux-foundation.org>
Date:   Sat, 8 Jul 2023 09:42:57 +0800
Cc:     Muchun Song <songmuchun@bytedance.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        linux-kernel@vger.kernel.org
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Message-Id: <63EDE3B6-B0AD-4D67-8EC6-FC8AE627E352@linux.dev>
References: <20230707033859.16148-1-songmuchun@bytedance.com>
 <20230707123844.adf56ba3e0d000f6da431494@linux-foundation.org>
To:     Andrew Morton <akpm@linux-foundation.org>
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> On Jul 8, 2023, at 03:38, Andrew Morton <akpm@linux-foundation.org> =
wrote:
>=20
> On Fri,  7 Jul 2023 11:38:59 +0800 Muchun Song =
<songmuchun@bytedance.com> wrote:
>=20
>> The local variable @page in __split_vmemmap_huge_pmd() to obtain a =
pmd
>> page without holding page_table_lock may possiblely get the page =
table
>> page instead of a huge pmd page.  The effect may be in set_pte_at()
>> since we may pass an invalid page struct, if set_pte_at() wants to
>> access the page struct (e.g. CONFIG_PAGE_TABLE_CHECK is enabled), it
>> may crash the kernel.  So fix it. And inline =
__split_vmemmap_huge_pmd()
>> since it only has one user.
>=20
> Is this likely enough to justify a backport?
>=20
> I'm thinking "add cc:stable and merge into 6.6-rc1", so it hits =
-stable
> after a couple of months of testing.
>=20

Hi Andrew,

It is better to backport it to stable. Could you help me add it?

Thanks.