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[70.52.229.124]) by smtp.gmail.com with ESMTPSA id r17-20020ac87ef1000000b003edfb5d7637sm1731278qtc.73.2023.04.17.12.53.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Apr 2023 12:53:23 -0700 (PDT) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Mike Kravetz , Andrea Arcangeli , =?UTF-8?q?Mika=20Penttil=C3=A4?= , Andrew Morton , peterx@redhat.com, Axel Rasmussen , Nadav Amit , David Hildenbrand , linux-stable Subject: [PATCH v2 2/6] mm/hugetlb: Fix uffd-wp bit lost when unsharing happens Date: Mon, 17 Apr 2023 15:53:13 -0400 Message-Id: <20230417195317.898696-3-peterx@redhat.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230417195317.898696-1-peterx@redhat.com> References: <20230417195317.898696-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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). Cc: linux-stable Fixes: 166f3ecc0daf ("mm/hugetlb: hook page faults for uffd write protectio= n") Reported-by: Mike Kravetz Reviewed-by: David Hildenbrand Reviewed-by: Mike Kravetz Signed-off-by: Peter Xu --- mm/hugetlb.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 0213efaf31be..cd3a9d8f4b70 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5637,13 +5637,16 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, = struct vm_area_struct *vma, spin_lock(ptl); ptep =3D hugetlb_walk(vma, haddr, huge_page_size(h)); if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) { + pte_t newpte =3D 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 =3D 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 =3D page_folio(old_page); --=20 2.39.1