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[70.52.229.124]) by smtp.gmail.com with ESMTPSA id g3-20020ac81243000000b003ea1b97acfasm612446qtj.49.2023.04.13.16.11.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Apr 2023 16:11:25 -0700 (PDT) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Axel Rasmussen , Andrew Morton , David Hildenbrand , peterx@redhat.com, Mike Kravetz , Nadav Amit , Andrea Arcangeli , linux-stable Subject: [PATCH 2/6] mm/hugetlb: Fix uffd-wp bit lost when unsharing happens Date: Thu, 13 Apr 2023 19:11:16 -0400 Message-Id: <20230413231120.544685-3-peterx@redhat.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230413231120.544685-1-peterx@redhat.com> References: <20230413231120.544685-1-peterx@redhat.com> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1763105005297087628?= X-GMAIL-MSGID: =?utf-8?q?1763105005297087628?= 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 protection") Reported-by: Mike Kravetz Signed-off-by: Peter Xu Reviewed-by: David Hildenbrand Reviewed-by: Mike Kravetz --- mm/hugetlb.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 7320e64aacc6..083aae35bff8 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 = 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);