The patch titled Subject: mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page_range() has been added to the -mm mm-unstable branch. Its filename is mm-hugetlb-separate-path-for-hwpoison-entry-in-copy_hugetlb_page_range.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Naoya Horiguchi naoya.horiguchi@nec.com Subject: mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page_range() Date: Thu, 30 Jun 2022 11:27:48 +0900

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.

Link: https://lkml.kernel.org/r/20220630022755.3362349-3-naoya.horiguchi@linux.dev Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive") Signed-off-by: Naoya Horiguchi naoya.horiguchi@nec.com Reviewed-by: Miaohe Lin linmiaohe@huawei.com Reviewed-by: Mike Kravetz mike.kravetz@oracle.com Reviewed-by: Muchun Song songmuchun@bytedance.com Cc: stable@vger.kernel.org # 5.18 Cc: David Hildenbrand david@redhat.com Cc: Liu Shixin liushixin2@huawei.com Cc: Oscar Salvador osalvador@suse.de Cc: Yang Shi shy828301@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/hugetlb.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlb-separate-path-for-hwpoison-entry-in-copy_hugetlb_page_range +++ a/mm/hugetlb.c @@ -4803,8 +4803,13 @@ again: * sharing with another vma. */ ; - } else if (unlikely(is_hugetlb_entry_migration(entry) || - is_hugetlb_entry_hwpoisoned(entry))) { + } else if (unlikely(is_hugetlb_entry_hwpoisoned(entry))) { + bool uffd_wp = huge_pte_uffd_wp(entry); + + if (!userfaultfd_wp(dst_vma) && uffd_wp) + entry = huge_pte_clear_uffd_wp(entry); + set_huge_swap_pte_at(dst, addr, dst_pte, entry, sz); + } else if (unlikely(is_hugetlb_entry_migration(entry))) { swp_entry_t swp_entry = pte_to_swp_entry(entry); bool uffd_wp = huge_pte_uffd_wp(entry);

_

Patches currently in -mm which might be from naoya.horiguchi@nec.com are

mm-hugetlb-check-gigantic_page_runtime_supported-in-return_unused_surplus_pages.patch mm-hugetlb-separate-path-for-hwpoison-entry-in-copy_hugetlb_page_range.patch mm-hugetlb-make-pud_huge-and-follow_huge_pud-aware-of-non-present-pud-entry.patch mm-hwpoison-hugetlb-support-saving-mechanism-of-raw-error-pages.patch mm-hwpoison-make-unpoison-aware-of-raw-error-info-in-hwpoisoned-hugepage.patch mm-hwpoison-set-pg_hwpoison-for-busy-hugetlb-pages.patch mm-hwpoison-make-__page_handle_poison-returns-int.patch mm-hwpoison-skip-raw-hwpoison-page-in-freeing-1gb-hugepage.patch mm-hwpoison-enable-memory-error-handling-on-1gb-hugepage.patch