Re: [PATCH] migrate: Skip hwpoisoned hugetlb folios during migration

[Andrew Morton]

On Wed,  1 Jul 2026 18:55:44 +0800 Kaitao Cheng <kaitao.cheng@xxxxxxxxx> wrote:

> Date: Wed,  1 Jul 2026 18:55:44 +0800

Well.

> Hugetlb migration does not check whether the source folio contains
> hwpoisoned memory before trying to move it.  After the folio is unmapped,
> the move path can reach hugetlbfs_migrate_folio() and then
> migrate_huge_page_move_mapping(), which copies the source folio into the
> new folio.
> 
> That copy uses folio_mc_copy(), so architectures with recoverable
> machine-check copy support can fail the copy with -EHWPOISON.  However,
> there is no reason to attempt the move once the source folio is already
> known to contain poisoned memory.  Architectures without such copy_mc
> support also fall back to a normal copy, which can consume the poison.
> 
> Check folio_contain_hwpoisoned_page() after locking the source hugetlb
> folio and fail the migration with -EHWPOISON before unmapping or copying
> it.  This covers both a hwpoisoned hugetlb head folio and large folios
> that only have the has_hwpoisoned summary flag set.

As always: please provide a description of the userspace-visible
runtime effects of the bug.

Even better if you can present a reproducer.

> Fixes: 290408d4a250 ("hugetlb: hugepage migration core")

Oct, 2010.  So I'm assuming this isn't super-urgent.

otoh, now it's out there and known about, perhaps Bad Guys can find a
way of triggering this, so the urgency becomes higher.


Anyway, please consider the Sashiko report
(https://sashiko.dev/#/patchset/20260701105544.97059-1-kaitao.cheng@xxxxxxxxx)
then update the changelog with the above info.  Decide whether we
should cc:stable (and describe why) then resend?

Thanks.