The patch below does not apply to the 5.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From c2cb0dcce9dd8b748b6ca8bb8d4a389f2e232307 Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> Date: Mon, 4 Jul 2022 10:33:05 +0900 Subject: [PATCH] mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page_range() 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/20220704013312.2415700-3-naoya.horiguchi@xxxxxxxxx Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive") Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [5.18] Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Liu Shixin <liushixin2@xxxxxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxx> Cc: Yang Shi <shy828301@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a57e1be41401..baf7f6b19ce6 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4788,8 +4788,13 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, * 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_pte_at(dst, addr, dst_pte, entry); + } 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);
