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=-15.7 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,URIBL_BLOCKED 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 21CC9C2B9FB for ; Sun, 23 May 2021 00:41:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F2D376052B for ; Sun, 23 May 2021 00:41:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231455AbhEWAnP (ORCPT ); Sat, 22 May 2021 20:43:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:52248 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231451AbhEWAnN (ORCPT ); Sat, 22 May 2021 20:43:13 -0400 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 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org 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; /* _