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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id t35sm19789974qth.79.2020.08.02.12.18.36 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Sun, 02 Aug 2020 12:18:37 -0700 (PDT) Date: Sun, 2 Aug 2020 12:18:35 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Andrew Morton cc: "Kirill A. Shutemov" , Andrea Arcangeli , Song Liu , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] khugepaged: khugepaged_test_exit() check mmget_still_valid() In-Reply-To: Message-ID: References: User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Move collapse_huge_page()'s mmget_still_valid() check into khugepaged_test_exit() itself. collapse_huge_page() is used for anon THP only, and earned its mmget_still_valid() check because it inserts a huge pmd entry in place of the page table's pmd entry; whereas collapse_file()'s retract_page_tables() or collapse_pte_mapped_thp() merely clears the page table's pmd entry. But core dumping without mmap lock must have been as open to mistaking a racily cleared pmd entry for a page table at physical page 0, as exit_mmap() was. And we certainly have no interest in mapping as a THP once dumping core. Fixes: 59ea6d06cfa9 ("coredump: fix race condition between collapse_huge_page() and core dumping") Signed-off-by: Hugh Dickins Cc: stable@vger.kernel.org # v4.8+ --- Note on stable backporting: the coredump fix was backported as far as v3.16, but this extension only needed where shmem or file THP supported. mm/khugepaged.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) --- 5.8-rc7/mm/khugepaged.c 2020-07-26 16:58:02.189038680 -0700 +++ linux/mm/khugepaged.c 2020-08-02 10:56:11.105617241 -0700 @@ -431,7 +431,7 @@ static void insert_to_mm_slots_hash(stru static inline int khugepaged_test_exit(struct mm_struct *mm) { - return atomic_read(&mm->mm_users) == 0; + return atomic_read(&mm->mm_users) == 0 || !mmget_still_valid(mm); } static bool hugepage_vma_check(struct vm_area_struct *vma, @@ -1100,9 +1100,6 @@ static void collapse_huge_page(struct mm * handled by the anon_vma lock + PG_lock. */ mmap_write_lock(mm); - result = SCAN_ANY_PROCESS; - if (!mmget_still_valid(mm)) - goto out; result = hugepage_vma_revalidate(mm, address, &vma); if (result) goto out; From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7DACFC433E0 for ; Sun, 2 Aug 2020 19:18:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 380DC206F6 for ; Sun, 2 Aug 2020 19:18:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="sHovUWig" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 380DC206F6 Authentication-Results: mail.kernel.org; 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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id t35sm19789974qth.79.2020.08.02.12.18.36 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Sun, 02 Aug 2020 12:18:37 -0700 (PDT) Date: Sun, 2 Aug 2020 12:18:35 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Andrew Morton cc: "Kirill A. Shutemov" , Andrea Arcangeli , Song Liu , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] khugepaged: khugepaged_test_exit() check mmget_still_valid() In-Reply-To: Message-ID: References: User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Rspamd-Queue-Id: 4C6DF1AD1B0 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Move collapse_huge_page()'s mmget_still_valid() check into khugepaged_test_exit() itself. collapse_huge_page() is used for anon THP only, and earned its mmget_still_valid() check because it inserts a huge pmd entry in place of the page table's pmd entry; whereas collapse_file()'s retract_page_tables() or collapse_pte_mapped_thp() merely clears the page table's pmd entry. But core dumping without mmap lock must have been as open to mistaking a racily cleared pmd entry for a page table at physical page 0, as exit_mmap() was. And we certainly have no interest in mapping as a THP once dumping core. Fixes: 59ea6d06cfa9 ("coredump: fix race condition between collapse_huge_page() and core dumping") Signed-off-by: Hugh Dickins Cc: stable@vger.kernel.org # v4.8+ --- Note on stable backporting: the coredump fix was backported as far as v3.16, but this extension only needed where shmem or file THP supported. mm/khugepaged.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) --- 5.8-rc7/mm/khugepaged.c 2020-07-26 16:58:02.189038680 -0700 +++ linux/mm/khugepaged.c 2020-08-02 10:56:11.105617241 -0700 @@ -431,7 +431,7 @@ static void insert_to_mm_slots_hash(stru static inline int khugepaged_test_exit(struct mm_struct *mm) { - return atomic_read(&mm->mm_users) == 0; + return atomic_read(&mm->mm_users) == 0 || !mmget_still_valid(mm); } static bool hugepage_vma_check(struct vm_area_struct *vma, @@ -1100,9 +1100,6 @@ static void collapse_huge_page(struct mm * handled by the anon_vma lock + PG_lock. */ mmap_write_lock(mm); - result = SCAN_ANY_PROCESS; - if (!mmget_still_valid(mm)) - goto out; result = hugepage_vma_revalidate(mm, address, &vma); if (result) goto out;