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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 E6087C47404 for ; Fri, 11 Oct 2019 14:06:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C66A720679 for ; Fri, 11 Oct 2019 14:06:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728734AbfJKOGr (ORCPT ); Fri, 11 Oct 2019 10:06:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43338 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728149AbfJKOGr (ORCPT ); Fri, 11 Oct 2019 10:06:47 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4DB19307C829; Fri, 11 Oct 2019 14:06:46 +0000 (UTC) Received: from t460s.redhat.com (ovpn-117-27.ams2.redhat.com [10.36.117.27]) by smtp.corp.redhat.com (Postfix) with ESMTP id CBF8B5D721; Fri, 11 Oct 2019 14:06:38 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Qian Cai , Andrew Morton , Vlastimil Babka , Michal Hocko , Thomas Gleixner , "Peter Zijlstra (Intel)" , Miles Chen , Mike Rapoport , Greg Kroah-Hartman , David Hildenbrand Subject: [PATCH v2] mm/page_owner: Don't access uninitialized memmaps when reading /proc/pagetypeinfo Date: Fri, 11 Oct 2019 16:06:38 +0200 Message-Id: <20191011140638.8160-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Fri, 11 Oct 2019 14:06:46 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Qian Cai Uninitialized memmaps contain garbage and in the worst case trigger kernel BUGs, especially with CONFIG_PAGE_POISONING. They should not get touched. For example, when not onlining a memory block that is spanned by a zone and reading /proc/pagetypeinfo with CONFIG_DEBUG_VM_PGFLAGS and CONFIG_PAGE_POISONING, we can trigger a kernel BUG: :/# echo 1 > /sys/devices/system/memory/memory40/online :/# echo 1 > /sys/devices/system/memory/memory42/online :/# cat /proc/pagetypeinfo > test.file [ 42.489856] page:fffff2c585200000 is uninitialized and poisoned [ 42.489861] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff [ 42.492235] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff [ 42.493501] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) [ 42.494533] There is not page extension available. [ 42.495358] ------------[ cut here ]------------ [ 42.496163] kernel BUG at include/linux/mm.h:1107! [ 42.497069] invalid opcode: 0000 [#1] SMP NOPTI Please not that this change does not affect ZONE_DEVICE, because pagetypeinfo_showmixedcount_print() is called from mm/vmstat.c:pagetypeinfo_showmixedcount() only for populated zones, and ZONE_DEVICE is never populated (zone->present_pages always 0). Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") # visible after d0dc12e86b319 Signed-off-by: Qian Cai Cc: Andrew Morton Cc: Vlastimil Babka Cc: Michal Hocko Cc: Thomas Gleixner Cc: "Peter Zijlstra (Intel)" Cc: Miles Chen Cc: Mike Rapoport Cc: Qian Cai Cc: Greg Kroah-Hartman [ move check to outer loop, add comment, rephrase description ] Signed-off-by: David Hildenbrand --- Cai asked me to follow up on: [PATCH] mm/page_owner: fix a crash after memory offline --- mm/page_owner.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/page_owner.c b/mm/page_owner.c index dee931184788..7d149211f6be 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -284,7 +284,8 @@ void pagetypeinfo_showmixedcount_print(struct seq_file *m, * not matter as the mixed block count will still be correct */ for (; pfn < end_pfn; ) { - if (!pfn_valid(pfn)) { + page = pfn_to_online_page(pfn); + if (!page) { pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES); continue; } @@ -292,13 +293,13 @@ void pagetypeinfo_showmixedcount_print(struct seq_file *m, block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); block_end_pfn = min(block_end_pfn, end_pfn); - page = pfn_to_page(pfn); pageblock_mt = get_pageblock_migratetype(page); for (; pfn < block_end_pfn; pfn++) { if (!pfn_valid_within(pfn)) continue; + /* The pageblock is online, no need to recheck. */ page = pfn_to_page(pfn); if (page_zone(page) != zone) -- 2.21.0