From nobody Mon May 4 11:29:37 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 49A6BC433EF for ; Mon, 13 Jun 2022 17:42:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231321AbiFMRls (ORCPT ); Mon, 13 Jun 2022 13:41:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48194 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348062AbiFMRkx (ORCPT ); Mon, 13 Jun 2022 13:40:53 -0400 Received: from out30-44.freemail.mail.aliyun.com (out30-44.freemail.mail.aliyun.com [115.124.30.44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E85839800; Mon, 13 Jun 2022 06:10:53 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R851e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046060;MF=xianting.tian@linux.alibaba.com;NM=1;PH=DS;RN=11;SR=0;TI=SMTPD_---0VGHIWD._1655125849; Received: from localhost(mailfrom:xianting.tian@linux.alibaba.com fp:SMTPD_---0VGHIWD._1655125849) by smtp.aliyun-inc.com; Mon, 13 Jun 2022 21:10:50 +0800 From: Xianting Tian To: akpm@linux-foundation.org, vbabka@suse.cz, ziy@nvidia.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, huanyi.xj@alibaba-inc.com, guoren@kernel.org, zjb194813@alibaba-inc.com, tianhu.hh@alibaba-inc.com, Xianting Tian Subject: [RESEND PATCH] mm: page_alloc: validate buddy before check the migratetype Date: Mon, 13 Jun 2022 21:10:46 +0800 Message-Id: <20220613131046.3009889-1-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.") added buddy check code. But unfortunately, this fix isn't backported to linux-5.17.y and the former stable branches. The reason is it added wrong fixes message: Fixes: 1dd214b8f21c ("mm: page_alloc: avoid merging non-fallbackable pageblocks with others") Actually, this issue is involved by commit: commit d9dddbf55667 ("mm/page_alloc: prevent merging between isolated = and other pageblocks") For RISC-V arch, the first 2M is reserved for sbi, so the start PFN is 512, but it got buddy PFN 0 for PFN 0x2000: 0 =3D 0x2000 ^ (1 << 12) With the illegal buddy PFN 0, it got an illegal buddy page, which caused crash in __get_pfnblock_flags_mask(). With the patch, it can avoid the calling of get_pageblock_migratetype() if it isn't buddy page. 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 Reviewed-by: Guo Ren --- mm/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b1caa1c6c887..5b423caa68fd 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1129,6 +1129,9 @@ static inline void __free_one_page(struct page *page, =20 buddy_pfn =3D __find_buddy_pfn(pfn, order); buddy =3D page + (buddy_pfn - pfn); + + 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