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 E8A74C433E1 for ; Mon, 24 Aug 2020 09:32:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C5FC620738 for ; Mon, 24 Aug 2020 09:32:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598261539; bh=A57CuqgnKgu/vD9IuTu09MWYcdZZSsFtJI1yNs7c7Yw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=1kvVafdkUk7g/4WeNpdHvXZpX4PQE9k9xYSfdFwDAfcdzKNEn+EVPZp/DCf0t4NJX NBZ5dwi7jIq7kDpBYbHB9I/QngLe0rs2jekmi1dpKrC+HMEpawLw1FrKKU6dsWYx3z hObF1WL9C4UTRaLYqhq+4jZgS2NcF6oX7p3yXL+U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729506AbgHXIuF (ORCPT ); Mon, 24 Aug 2020 04:50:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:52898 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729802AbgHXIt5 (ORCPT ); Mon, 24 Aug 2020 04:49:57 -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 3D400207D3; Mon, 24 Aug 2020 08:49:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598258996; bh=A57CuqgnKgu/vD9IuTu09MWYcdZZSsFtJI1yNs7c7Yw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YpwfCtfNbRtNSphixWA4Q69hDI8+IVugvFKv+hk9ywg3DMr8lYIEwhE/kcjFZ3Dm8 Doem8EJsp3hZQDN+ajUo4vIP506BvX/5dy2Crt2sAdAWDPvycNvjk6sngTR5XZdf6z dzO7nKZDZh52xYLuesAZyuB9xjkFT5FUFmt/PALo= 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 4.4 07/33] khugepaged: khugepaged_test_exit() check mmget_still_valid() Date: Mon, 24 Aug 2020 10:31:03 +0200 Message-Id: <20200824082346.885173926@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200824082346.498653578@linuxfoundation.org> References: <20200824082346.498653578@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/huge_memory.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index c5628ebc0fc29..1c4d7d2f53d22 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2136,7 +2136,7 @@ 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) @@ -2587,9 +2587,6 @@ 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; if (unlikely(khugepaged_test_exit(mm))) goto out; -- 2.25.1