From patchwork Sun May 23 00:41:46 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 12274703 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 CF6F7C2B9F2 for ; Sun, 23 May 2021 00:41:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 81C776052B for ; Sun, 23 May 2021 00:41:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 81C776052B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 20FE18E0092; Sat, 22 May 2021 20:41:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1E6528E007F; Sat, 22 May 2021 20:41:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 087CE8E0092; Sat, 22 May 2021 20:41:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0088.hostedemail.com [216.40.44.88]) by kanga.kvack.org (Postfix) with ESMTP id CD7CD8E007F for ; Sat, 22 May 2021 20:41:48 -0400 (EDT) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 67ABD181AEF39 for ; Sun, 23 May 2021 00:41:48 +0000 (UTC) X-FDA: 78170643096.23.7350F01 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf01.hostedemail.com (Postfix) with ESMTP id 1FFCC500152E for ; Sun, 23 May 2021 00:41:43 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 2A4006100A; Sun, 23 May 2021 00:41:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1621730507; bh=3fW0FdmKsOra4/oaJJ8MdrIu64EXewmHrtjyfJU8dRs=; h=Date:From:To:Subject:In-Reply-To:From; b=n5pwPKVO7Ui5sJuOA/TZDKGQrzzfgGnjgJIsDljw2ScUt2dooJWEFKm0/f5/ITtqV gyn4wgcb2fCorfukNfZLWjpoyH0Pl1nq6/fnpwmw67j0lzfKDZzv52KHeRzz7Bz0ZA n4YDFF8WHOGiKDXxA4Q1jTSMMB5DjInvVCdmaKnU= Date: Sat, 22 May 2021 17:41:46 -0700 From: Andrew Morton To: akpm@linux-foundation.org, david@redhat.com, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, stable@vger.kernel.org, torvalds@linux-foundation.org, yaoaili@kingsoft.com Subject: [patch 02/10] Revert "mm/gup: check page posion status for coredump." Message-ID: <20210523004146.Uqko6SWcY%akpm@linux-foundation.org> In-Reply-To: <20210522174113.47fd4c853c0a1470c57deefa@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Rspamd-Queue-Id: 1FFCC500152E Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=n5pwPKVO; spf=pass (imf01.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Rspamd-Server: rspam04 X-Stat-Signature: ua6fbzcfbgbontm33zm7j7eobtubxixx X-HE-Tag: 1621730503-940935 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: From: Michal Hocko Subject: Revert "mm/gup: check page posion status for coredump." While reviewing http://lkml.kernel.org/r/20210429122519.15183-4-david@redhat.com I have crossed d3378e86d182 ("mm/gup: check page posion status for coredump.") and noticed that this patch is broken in two ways. First it doesn't really prevent hwpoison pages from being dumped because hwpoison pages can be marked asynchornously at any time after the check. Secondly, and more importantly, the patch introduces a ref count leak because get_dump_page takes a reference on the page which is not released. It also seems that the patch was merged incorrectly because there were follow up changes not included as well as discussions on how to address the underlying problem http://lkml.kernel.org/r/57ac524c-b49a-99ec-c1e4-ef5027bfb61b@redhat.com Therefore revert the original patch. Link: https://lkml.kernel.org/r/20210505135407.31590-1-mhocko@kernel.org Fixes: d3378e86d182 ("mm/gup: check page posion status for coredump.") Signed-off-by: Michal Hocko Reviewed-by: David Hildenbrand Cc: Aili Yao Cc: Signed-off-by: Andrew Morton --- mm/gup.c | 4 ---- mm/internal.h | 20 -------------------- 2 files changed, 24 deletions(-) --- a/mm/gup.c~revert-mm-gup-check-page-posion-status-for-coredump +++ a/mm/gup.c @@ -1593,10 +1593,6 @@ struct page *get_dump_page(unsigned long FOLL_FORCE | FOLL_DUMP | FOLL_GET); if (locked) mmap_read_unlock(mm); - - if (ret == 1 && is_page_poisoned(page)) - return NULL; - return (ret == 1) ? page : NULL; } #endif /* CONFIG_ELF_CORE */ --- a/mm/internal.h~revert-mm-gup-check-page-posion-status-for-coredump +++ a/mm/internal.h @@ -96,26 +96,6 @@ static inline void set_page_refcounted(s set_page_count(page, 1); } -/* - * When kernel touch the user page, the user page may be have been marked - * poison but still mapped in user space, if without this page, the kernel - * can guarantee the data integrity and operation success, the kernel is - * better to check the posion status and avoid touching it, be good not to - * panic, coredump for process fatal signal is a sample case matching this - * scenario. Or if kernel can't guarantee the data integrity, it's better - * not to call this function, let kernel touch the poison page and get to - * panic. - */ -static inline bool is_page_poisoned(struct page *page) -{ - if (PageHWPoison(page)) - return true; - else if (PageHuge(page) && PageHWPoison(compound_head(page))) - return true; - - return false; -} - extern unsigned long highest_memmap_pfn; /*