The patch titled Subject: mm/hugetlb: fix uffd-wp bit lost when unsharing happens has been added to the -mm mm-unstable branch. Its filename is mm-hugetlb-fix-uffd-wp-bit-lost-when-unsharing-happens.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: Peter Xu peterx@redhat.com Subject: mm/hugetlb: fix uffd-wp bit lost when unsharing happens Date: Mon, 17 Apr 2023 15:53:13 -0400

When we try to unshare a pinned page for a private hugetlb, uffd-wp bit can get lost during unsharing. Fix it by carrying it over.

This should be very rare, only if an unsharing happened on a private hugetlb page with uffd-wp protected (e.g. in a child which shares the same page with parent with UFFD_FEATURE_EVENT_FORK enabled).

Link: https://lkml.kernel.org/r/20230417195317.898696-3-peterx@redhat.com Fixes: 166f3ecc0daf ("mm/hugetlb: hook page faults for uffd write protection") Signed-off-by: Peter Xu peterx@redhat.com Reported-by: Mike Kravetz mike.kravetz@oracle.com Reviewed-by: David Hildenbrand david@redhat.com Reviewed-by: Mike Kravetz mike.kravetz@oracle.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: Axel Rasmussen axelrasmussen@google.com Cc: Mika Penttil�� mpenttil@redhat.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 | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlb-fix-uffd-wp-bit-lost-when-unsharing-happens +++ a/mm/hugetlb.c @@ -5644,13 +5644,16 @@ retry_avoidcopy: spin_lock(ptl); ptep = hugetlb_walk(vma, haddr, huge_page_size(h)); if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) { + pte_t newpte = make_huge_pte(vma, &new_folio->page, !unshare); + /* Break COW or unshare */ huge_ptep_clear_flush(vma, haddr, ptep); mmu_notifier_invalidate_range(mm, range.start, range.end); page_remove_rmap(old_page, vma, true); hugepage_add_new_anon_rmap(new_folio, vma, haddr); - set_huge_pte_at(mm, haddr, ptep, - make_huge_pte(vma, &new_folio->page, !unshare)); + if (huge_pte_uffd_wp(pte)) + newpte = huge_pte_mkuffd_wp(newpte); + set_huge_pte_at(mm, haddr, ptep, newpte); folio_set_hugetlb_migratable(new_folio); /* Make the old page be freed below */ new_folio = page_folio(old_page); _

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