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=-13.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 F213FC433E3 for ; Mon, 24 Aug 2020 09:26:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C786C2074D for ; Mon, 24 Aug 2020 09:26:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598261200; bh=qVU8jQNWyLlXjnrNh2gzlHqO6Dq7uBhUCkw5dhQOHOk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=fgfDYTR3xoR6TxY1K2r8qvnqAW9XHC3oJKWLFmIo0yaP0Gthd16qQjVrmRxoKkZvv Rj52uNnY4CVIuGgymtZmz8yM1K8zhwlUBUl/UF0IluBzi7s28v/J+LFL0CYKKAaJdF tUiye6ej8tyJT8AtFXGuRtaM/mxr9nk/B5mOvRx4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729448AbgHXJ0i (ORCPT ); Mon, 24 Aug 2020 05:26:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:59926 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730132AbgHXIxB (ORCPT ); Mon, 24 Aug 2020 04:53:01 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 17A7B2072D; Mon, 24 Aug 2020 08:53:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598259180; bh=qVU8jQNWyLlXjnrNh2gzlHqO6Dq7uBhUCkw5dhQOHOk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FfEmtYUTxaOLFbvF8srDq8B/fbQuggL22l1qeYQVZLTgkQu0bVeIeJsioUDThRzoy qKo2JPOgqLzP+CJ9pRrG1TQplgBf4qnRVqrimH74UiebnPSUx2HARvyq5NHV5TIjWA Sgx8n6B3Qfwv3QaEPiA+X9/x/7QGykP7tWy8+lUI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hugh Dickins , Andrew Morton , Andrea Arcangeli , Song Liu , Mike Kravetz , "Kirill A. Shutemov" , Linus Torvalds , Sasha Levin Subject: [PATCH 4.14 03/50] khugepaged: khugepaged_test_exit() check mmget_still_valid() Date: Mon, 24 Aug 2020 10:31:04 +0200 Message-Id: <20200824082352.040818505@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200824082351.823243923@linuxfoundation.org> References: <20200824082351.823243923@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Hugh Dickins [ Upstream commit bbe98f9cadff58cdd6a4acaeba0efa8565dabe65 ] 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 Signed-off-by: Andrew Morton Cc: Andrea Arcangeli Cc: Song Liu Cc: Mike Kravetz Cc: Kirill A. Shutemov Cc: [4.8+] Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008021217020.27773@eggly.anvils Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/khugepaged.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 04b4c38d0c184..a1b7475c05d04 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -394,7 +394,7 @@ static void insert_to_mm_slots_hash(struct mm_struct *mm, 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); } int __khugepaged_enter(struct mm_struct *mm) @@ -1006,9 +1006,6 @@ static void collapse_huge_page(struct mm_struct *mm, * handled by the anon_vma lock + PG_lock. */ down_write(&mm->mmap_sem); - result = SCAN_ANY_PROCESS; - if (!mmget_still_valid(mm)) - goto out; result = hugepage_vma_revalidate(mm, address, &vma); if (result) goto out; -- 2.25.1