Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753663AbdFSShb (ORCPT + 2 others); Mon, 19 Jun 2017 14:37:31 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:52502 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753614AbdFSSh0 (ORCPT ); Mon, 19 Jun 2017 14:37:26 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Toshi Kani , Andrew Banman , Reza Arbab , Greg KH , Andrew Morton , Linus Torvalds , Willy Tarreau Subject: [PATCH 3.10 139/268] mm/memory_hotplug.c: check start_pfn in test_pages_in_a_zone() Date: Mon, 19 Jun 2017 20:30:38 +0200 Message-Id: <1497897167-14556-140-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1497897167-14556-1-git-send-email-w@1wt.eu> References: <1497897167-14556-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Toshi Kani commit deb88a2a19e85842d79ba96b05031739ec327ff4 upstream. Patch series "fix a kernel oops when reading sysfs valid_zones", v2. A sysfs memory file is created for each 2GiB memory block on x86-64 when the system has 64GiB or more memory. [1] When the start address of a memory block is not backed by struct page, i.e. a memory range is not aligned by 2GiB, reading its 'valid_zones' attribute file leads to a kernel oops. This issue was observed on multiple x86-64 systems with more than 64GiB of memory. This patch-set fixes this issue. Patch 1 first fixes an issue in test_pages_in_a_zone(), which does not test the start section. Patch 2 then fixes the kernel oops by extending test_pages_in_a_zone() to return valid [start, end). Note for stable kernels: The memory block size change was made by commit bdee237c0343 ("x86: mm: Use 2GB memory block size on large-memory x86-64 systems"), which was accepted to 3.9. However, this patch-set depends on (and fixes) the change to test_pages_in_a_zone() made by commit 5f0f2887f4de ("mm/memory_hotplug.c: check for missing sections in test_pages_in_a_zone()"), which was accepted to 4.4. So, I recommend that we backport it up to 4.4. [1] 'Commit bdee237c0343 ("x86: mm: Use 2GB memory block size on large-memory x86-64 systems")' This patch (of 2): test_pages_in_a_zone() does not check 'start_pfn' when it is aligned by section since 'sec_end_pfn' is set equal to 'pfn'. Since this function is called for testing the range of a sysfs memory file, 'start_pfn' is always aligned by section. Fix it by properly setting 'sec_end_pfn' to the next section pfn. Also make sure that this function returns 1 only when the range belongs to a zone. Link: http://lkml.kernel.org/r/20170127222149.30893-2-toshi.kani@hpe.com Signed-off-by: Toshi Kani Cc: Andrew Banman Cc: Reza Arbab Cc: Greg KH Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Willy Tarreau --- mm/memory_hotplug.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 7f1bf93..9deb93d 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1205,7 +1205,7 @@ int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages) } /* - * Confirm all pages in a range [start, end) is belongs to the same zone. + * Confirm all pages in a range [start, end) belong to the same zone. */ static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn) { @@ -1213,9 +1213,9 @@ static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn) struct zone *zone = NULL; struct page *page; int i; - for (pfn = start_pfn, sec_end_pfn = SECTION_ALIGN_UP(start_pfn); + for (pfn = start_pfn, sec_end_pfn = SECTION_ALIGN_UP(start_pfn + 1); pfn < end_pfn; - pfn = sec_end_pfn + 1, sec_end_pfn += PAGES_PER_SECTION) { + pfn = sec_end_pfn, sec_end_pfn += PAGES_PER_SECTION) { /* Make sure the memory section is present first */ if (!present_section_nr(pfn_to_section_nr(pfn))) continue; @@ -1234,7 +1234,11 @@ static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn) zone = page_zone(page); } } - return 1; + + if (zone) + return 1; + else + return 0; } /* -- 2.8.0.rc2.1.gbe9624a