From c2cb0dcce9dd8b748b6ca8bb8d4a389f2e232307 Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi 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@linux.dev Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive") Signed-off-by: Naoya Horiguchi Reviewed-by: Miaohe Lin Reviewed-by: Mike Kravetz Reviewed-by: Muchun Song Cc: [5.18] Cc: David Hildenbrand Cc: Liu Shixin Cc: Oscar Salvador Cc: Yang Shi Signed-off-by: Andrew Morton --- mm/hugetlb.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) 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 @@ 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_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); -- 2.25.1