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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71AE7C433F5 for ; Mon, 18 Apr 2022 14:03:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244182AbiDROFw (ORCPT ); Mon, 18 Apr 2022 10:05:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244926AbiDRNsh (ORCPT ); Mon, 18 Apr 2022 09:48:37 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 764CE338B8; Mon, 18 Apr 2022 06:01:17 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id D831B603E0; Mon, 18 Apr 2022 13:01:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EBCE1C385A7; Mon, 18 Apr 2022 13:01:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1650286876; bh=m2wwDRKEUb1FSsfsa8zID9Em893Bo+8xBvdGNWAui70=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=g1CICoKlpggb6chhetbOUQxXPyCO1P3PTX5P0kzSYKBf+suvVik4iyHvbaAb/a2la iKTm9czw5MWbwIbG85RyHxX5/hNTLlUCDf3Wnyh1CLv2aYlPJ7ZBtqOibVb6WV4IXI 4VBlGEG6VxvCR356uUQlsmG1eZVKYhyqEUaKg34Q= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Waiman Long , Justin Forbes , "Kirill A . Shutemov" , Ingo Molnar , Rafael Aquini , Andrew Morton , Linus Torvalds Subject: [PATCH 4.14 256/284] mm/sparsemem: fix mem_section will never be NULL gcc 12 warning Date: Mon, 18 Apr 2022 14:13:57 +0200 Message-Id: <20220418121219.686110669@linuxfoundation.org> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20220418121210.689577360@linuxfoundation.org> References: <20220418121210.689577360@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Waiman Long commit a431dbbc540532b7465eae4fc8b56a85a9fc7d17 upstream. The gcc 12 compiler reports a "'mem_section' will never be NULL" warning on the following code: static inline struct mem_section *__nr_to_section(unsigned long nr) { #ifdef CONFIG_SPARSEMEM_EXTREME if (!mem_section) return NULL; #endif if (!mem_section[SECTION_NR_TO_ROOT(nr)]) return NULL; : It happens with CONFIG_SPARSEMEM_EXTREME off. The mem_section definition is #ifdef CONFIG_SPARSEMEM_EXTREME extern struct mem_section **mem_section; #else extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]; #endif In the !CONFIG_SPARSEMEM_EXTREME case, mem_section is a static 2-dimensional array and so the check "!mem_section[SECTION_NR_TO_ROOT(nr)]" doesn't make sense. Fix this warning by moving the "!mem_section[SECTION_NR_TO_ROOT(nr)]" check up inside the CONFIG_SPARSEMEM_EXTREME block and adding an explicit NR_SECTION_ROOTS check to make sure that there is no out-of-bound array access. Link: https://lkml.kernel.org/r/20220331180246.2746210-1-longman@redhat.com Fixes: 3e347261a80b ("sparsemem extreme implementation") Signed-off-by: Waiman Long Reported-by: Justin Forbes Cc: "Kirill A . Shutemov" Cc: Ingo Molnar Cc: Rafael Aquini Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- include/linux/mmzone.h | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1160,13 +1160,16 @@ extern struct mem_section mem_section[NR static inline struct mem_section *__nr_to_section(unsigned long nr) { + unsigned long root = SECTION_NR_TO_ROOT(nr); + + if (unlikely(root >= NR_SECTION_ROOTS)) + return NULL; + #ifdef CONFIG_SPARSEMEM_EXTREME - if (!mem_section) + if (!mem_section || !mem_section[root]) return NULL; #endif - if (!mem_section[SECTION_NR_TO_ROOT(nr)]) - return NULL; - return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK]; + return &mem_section[root][nr & SECTION_ROOT_MASK]; } extern int __section_nr(struct mem_section* ms); extern unsigned long usemap_size(void);