From: Peter Xu peterx@redhat.com
commit 5a2f8d22ace4c8ac8798fab836dca7350fa710b1 upstream.
Patch series "mm/hugetlb: More fixes around uffd-wp vs fork() / RO pins", v2.
This patch (of 6):
There're a bunch of things that were wrong:
- Reading uffd-wp bit from a swap entry should use pte_swp_uffd_wp() rather than huge_pte_uffd_wp().
- When copying over a pte, we should drop uffd-wp bit when !EVENT_FORK (aka, when !userfaultfd_wp(dst_vma)).
- When doing early CoW for private hugetlb (e.g. when the parent page was pinned), uffd-wp bit should be properly carried over if necessary.
No bug reported probably because most people do not even care about these corner cases, but they are still bugs and can be exposed by the recent unit tests introduced, so fix all of them in one shot.
Link: https://lkml.kernel.org/r/20230417195317.898696-1-peterx@redhat.com Link: https://lkml.kernel.org/r/20230417195317.898696-2-peterx@redhat.com Fixes: bc70fbf269fd ("mm/hugetlb: handle uffd-wp during fork()") Signed-off-by: Peter Xu peterx@redhat.com Reviewed-by: David Hildenbrand david@redhat.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: Axel Rasmussen axelrasmussen@google.com Cc: Mika Penttilä mpenttil@redhat.com Cc: Mike Kravetz mike.kravetz@oracle.com Cc: Nadav Amit nadav.amit@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/hugetlb.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-)
--- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4949,11 +4949,15 @@ static bool is_hugetlb_entry_hwpoisoned(
static void hugetlb_install_folio(struct vm_area_struct *vma, pte_t *ptep, unsigned long addr, - struct folio *new_folio) + struct folio *new_folio, pte_t old) { + pte_t newpte = make_huge_pte(vma, &new_folio->page, 1); + __folio_mark_uptodate(new_folio); hugepage_add_new_anon_rmap(new_folio, vma, addr); - set_huge_pte_at(vma->vm_mm, addr, ptep, make_huge_pte(vma, &new_folio->page, 1)); + if (userfaultfd_wp(vma) && huge_pte_uffd_wp(old)) + newpte = huge_pte_mkuffd_wp(newpte); + set_huge_pte_at(vma->vm_mm, addr, ptep, newpte); hugetlb_count_add(pages_per_huge_page(hstate_vma(vma)), vma->vm_mm); folio_set_hugetlb_migratable(new_folio); } @@ -5028,14 +5032,12 @@ again: */ ; } else if (unlikely(is_hugetlb_entry_hwpoisoned(entry))) { - bool uffd_wp = huge_pte_uffd_wp(entry); - - if (!userfaultfd_wp(dst_vma) && uffd_wp) + if (!userfaultfd_wp(dst_vma)) 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); + bool uffd_wp = pte_swp_uffd_wp(entry);
if (!is_readable_migration_entry(swp_entry) && cow) { /* @@ -5046,10 +5048,10 @@ again: swp_offset(swp_entry)); entry = swp_entry_to_pte(swp_entry); if (userfaultfd_wp(src_vma) && uffd_wp) - entry = huge_pte_mkuffd_wp(entry); + entry = pte_swp_mkuffd_wp(entry); set_huge_pte_at(src, addr, src_pte, entry); } - if (!userfaultfd_wp(dst_vma) && uffd_wp) + if (!userfaultfd_wp(dst_vma)) entry = huge_pte_clear_uffd_wp(entry); set_huge_pte_at(dst, addr, dst_pte, entry); } else if (unlikely(is_pte_marker(entry))) { @@ -5109,7 +5111,8 @@ again: /* huge_ptep of dst_pte won't change as in child */ goto again; } - hugetlb_install_folio(dst_vma, dst_pte, addr, new_folio); + hugetlb_install_folio(dst_vma, dst_pte, addr, + new_folio, src_pte_old); spin_unlock(src_ptl); spin_unlock(dst_ptl); continue; @@ -5127,6 +5130,9 @@ again: entry = huge_pte_wrprotect(entry); }
+ if (!userfaultfd_wp(dst_vma)) + entry = huge_pte_clear_uffd_wp(entry); + set_huge_pte_at(dst, addr, dst_pte, entry); hugetlb_count_add(npages, dst); }