Re: [mm-unstable PATCH v4 2/9] mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page_range()

[Andrew Morton]

On Mon,  4 Jul 2022 10:33:05 +0900 Naoya Horiguchi <naoya.horiguchi@xxxxxxxxx> wrote:

> Originally copy_hugetlb_page_range() handles migration entries and hwpoisoned
> 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 forking processes with hwpoison entries in pmd.
> 
> Separate the if branch into one for hwpoison entries and one for migration
> entries.
> 
> ...
>
> Cc: <stable@xxxxxxxxxxxxxxx> # 5.18

It's unusual to have a cc:stable patch in the middle of a series like
this.  One would expect the fix to be a standalone thing against
current -linus.

As presented, this patch won't get into mainline until after 5.20-rc1. 
If that's OK then OK.  Otherwise I can shuffle things around and stage
this patch in mm-hotfixes?