The patch titled Subject: mm/hugetlb: fix uffd-wp during fork() has been added to the -mm mm-unstable branch. Its filename is mm-hugetlb-fix-uffd-wp-during-fork.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

Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days

------------------------------------------------------ From: Peter Xu peterx@redhat.com Subject: mm/hugetlb: fix uffd-wp during fork() Date: Mon, 17 Apr 2023 15:53:12 -0400

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 Penttil�� 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 ---

mm/hugetlb.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlb-fix-uffd-wp-during-fork +++ a/mm/hugetlb.c @@ -4953,11 +4953,15 @@ 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); } @@ -5032,14 +5036,12 @@ 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) { /* @@ -5050,10 +5052,10 @@ 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))) { @@ -5118,7 +5120,8 @@ 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; @@ -5136,6 +5139,9 @@ 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); } _

Patches currently in -mm which might be from peterx@redhat.com are

selftests-mm-update-gitignore-with-two-missing-tests.patch selftests-mm-dump-a-summary-in-run_vmtestssh.patch selftests-mm-merge-utilh-into-vm_utilh.patch selftests-mm-use-test_gen_progs-where-proper.patch selftests-mm-link-vm_utilc-always.patch selftests-mm-merge-default_huge_page_size-into-one.patch selftests-mm-use-pm_-macros-in-vm_utilsh.patch selftests-mm-reuse-pagemap_get_entry-in-vm_utilh.patch selftests-mm-test-uffdio_zeropage-only-when-hugetlb.patch selftests-mm-drop-test_uffdio_zeropage_eexist.patch selftests-mm-create-uffd-common.patch selftests-mm-split-uffd-tests-into-uffd-stress-and-uffd-unit-tests.patch selftests-mm-uffd_register.patch selftests-mm-uffd_open_devsys.patch selftests-mm-uffdio_api-test.patch selftests-mm-drop-global-mem_fd-in-uffd-tests.patch selftests-mm-drop-global-hpage_size-in-uffd-tests.patch selftests-mm-rename-uffd_stats-to-uffd_args.patch selftests-mm-let-uffd_handle_page_fault-take-wp-parameter.patch selftests-mm-allow-allocate_area-to-fail-properly.patch selftests-mm-add-framework-for-uffd-unit-test.patch selftests-mm-move-uffd-pagemap-test-to-unit-test.patch selftests-mm-move-uffd-minor-test-to-unit-test.patch selftests-mm-move-uffd-sig-events-tests-into-uffd-unit-tests.patch selftests-mm-move-zeropage-test-into-uffd-unit-tests.patch selftests-mm-workaround-no-way-to-detect-uffd-minor-wp.patch selftests-mm-allow-uffd-test-to-skip-properly-with-no-privilege.patch selftests-mm-drop-sys-dev-test-in-uffd-stress-test.patch selftests-mm-add-shmem-private-test-to-uffd-stress.patch selftests-mm-add-uffdio-register-ioctls-test.patch mm-hugetlb-fix-uffd-wp-during-fork.patch mm-hugetlb-fix-uffd-wp-bit-lost-when-unsharing-happens.patch selftests-mm-add-a-few-options-for-uffd-unit-test.patch selftests-mm-extend-and-rename-uffd-pagemap-test.patch selftests-mm-rename-cow_extra_libs-to-iouring_extra_libs.patch selftests-mm-add-tests-for-ro-pinning-vs-fork.patch