Re: [PATCH] mm: hugetlb_vmemmap: fix a race between vmemmap pmd split

[Andrew Morton]

On Fri,  7 Jul 2023 11:38:59 +0800 Muchun Song <songmuchun@xxxxxxxxxxxxx> 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.