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Date:   Fri, 7 Jul 2023 12:38:44 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Muchun Song <songmuchun@bytedance.com>
Cc:     mike.kravetz@oracle.com, muchun.song@linux.dev, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: hugetlb_vmemmap: fix a race between vmemmap pmd
 split
Message-Id: <20230707123844.adf56ba3e0d000f6da431494@linux-foundation.org>
In-Reply-To: <20230707033859.16148-1-songmuchun@bytedance.com>
References: <20230707033859.16148-1-songmuchun@bytedance.com>
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On Fri,  7 Jul 2023 11:38:59 +0800 Muchun Song <songmuchun@bytedance.com> wrote:

> 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.

Is this likely enough to justify a backport?

I'm thinking "add cc:stable and merge into 6.6-rc1", so it hits -stable
after a couple of months of testing.