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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 EA256C10F14 for ; Tue, 8 Oct 2019 15:29:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C43AC218DE for ; Tue, 8 Oct 2019 15:29:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727696AbfJHP3c (ORCPT ); Tue, 8 Oct 2019 11:29:32 -0400 Received: from mx2.suse.de ([195.135.220.15]:50234 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726134AbfJHP3c (ORCPT ); Tue, 8 Oct 2019 11:29:32 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 1D112B1B6; Tue, 8 Oct 2019 15:29:30 +0000 (UTC) From: Vlastimil Babka To: Andrew Morton , Mel Gorman , Florian Weimer , Dave Chinner Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Vlastimil Babka , stable@vger.kernel.org Subject: [PATCH] mm, compaction: fix wrong pfn handling in __reset_isolation_pfn() Date: Tue, 8 Oct 2019 17:29:15 +0200 Message-Id: <20191008152915.24704-1-vbabka@suse.cz> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Florian and Dave reported [1] a NULL pointer dereference in __reset_isolation_pfn(). While the exact cause is unclear, staring at the code revealed two bugs, which might be related. One bug is that if zone starts in the middle of pageblock, block_page might correspond to different pfn than block_pfn, and then the pfn_valid_within() checks will check different pfn's than those accessed via struct page. This might result in acessing an unitialized page in CONFIG_HOLES_IN_ZONE configs. The other bug is that end_page refers to the first page of next pageblock and not last page of current pageblock. The online and valid check is then wrong and with sections, the while (page < end_page) loop might wander off actual struct page arrays. [1] https://lore.kernel.org/linux-xfs/87o8z1fvqu.fsf@mid.deneb.enyo.de/ Reported-by: Florian Weimer Reported-by: Dave Chinner Fixes: 6b0868c820ff ("mm/compaction.c: correct zone boundary handling when resetting pageblock skip hints") Cc: Signed-off-by: Vlastimil Babka --- mm/compaction.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index ce08b39d85d4..672d3c78c6ab 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -270,14 +270,15 @@ __reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source, /* Ensure the start of the pageblock or zone is online and valid */ block_pfn = pageblock_start_pfn(pfn); - block_page = pfn_to_online_page(max(block_pfn, zone->zone_start_pfn)); + block_pfn = max(block_pfn, zone->zone_start_pfn); + block_page = pfn_to_online_page(block_pfn); if (block_page) { page = block_page; pfn = block_pfn; } /* Ensure the end of the pageblock or zone is online and valid */ - block_pfn += pageblock_nr_pages; + block_pfn = pageblock_end_pfn(pfn) - 1; block_pfn = min(block_pfn, zone_end_pfn(zone) - 1); end_page = pfn_to_online_page(block_pfn); if (!end_page) @@ -303,7 +304,7 @@ __reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source, page += (1 << PAGE_ALLOC_COSTLY_ORDER); pfn += (1 << PAGE_ALLOC_COSTLY_ORDER); - } while (page < end_page); + } while (page <= end_page); return false; } -- 2.23.0