From nobody Mon Apr 27 04:52:24 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CE096CCA483 for ; Thu, 16 Jun 2022 16:18:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378105AbiFPQSC (ORCPT ); Thu, 16 Jun 2022 12:18:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52278 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378061AbiFPQRy (ORCPT ); Thu, 16 Jun 2022 12:17:54 -0400 Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3EAFA1263E; Thu, 16 Jun 2022 09:17:52 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R651e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046049;MF=xianting.tian@linux.alibaba.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_---0VGaoY3U_1655396267; Received: from localhost(mailfrom:xianting.tian@linux.alibaba.com fp:SMTPD_---0VGaoY3U_1655396267) by smtp.aliyun-inc.com; Fri, 17 Jun 2022 00:17:48 +0800 From: Xianting Tian To: akpm@linux-foundation.org, ziy@nvidia.com, gregkh@linuxfoundation.org, stable@vger.kernel.org, guoren@kernel.org Cc: huanyi.xj@alibaba-inc.com, guohanjun@huawei.com, zjb194813@alibaba-inc.com, tianhu.hh@alibaba-inc.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xianting Tian Subject: [PATCH] mm: page_alloc: validate buddy page before using Date: Fri, 17 Jun 2022 00:17:40 +0800 Message-Id: <20220616161746.3565225-1-xianting.tian@linux.alibaba.com> X-Mailer: git-send-email 2.17.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Commit 787af64d05cd ("mm: page_alloc: validate buddy before check its migra= tetype.") fixes a bug in 1dd214b8f21c and there is a similar bug in d9dddbf55667 that can be fixed in a similar way too. In addition, for RISC-V arch the first 2MB RAM could be reserved for opensb= i, so it would have pfn_base=3D512 and mem_map began with 512th PFN when CONFIG_FLATMEM=3Dy. But __find_buddy_pfn algorithm thinks the start pfn 0, it could get 0 pfn or less than the pfn_base value. We need page_is_buddy() to verify the buddy to prevent accessing an invalid buddy. Fixes: d9dddbf55667 ("mm/page_alloc: prevent merging between isolated and o= ther pageblocks") Cc: stable@vger.kernel.org Reported-by: zjb194813@alibaba-inc.com Reported-by: tianhu.hh@alibaba-inc.com Signed-off-by: Xianting Tian --- mm/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a6e682569e5b..1c423faa4b62 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -864,6 +864,9 @@ static inline void __free_one_page(struct page *page, =20 buddy_idx =3D __find_buddy_index(page_idx, order); buddy =3D page + (buddy_idx - page_idx); + + if (!page_is_buddy(page, buddy, order)) + goto done_merging; buddy_mt =3D get_pageblock_migratetype(buddy); =20 if (migratetype !=3D buddy_mt --=20 2.17.1