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 2A8D1C433EF for ; Thu, 31 Mar 2022 21:53:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241593AbiCaVzi (ORCPT ); Thu, 31 Mar 2022 17:55:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34380 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239751AbiCaVzh (ORCPT ); Thu, 31 Mar 2022 17:55:37 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BA90A25CB for ; Thu, 31 Mar 2022 14:53:47 -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 sin.source.kernel.org (Postfix) with ESMTPS id D3F50CE2343 for ; Thu, 31 Mar 2022 21:53:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37963C340ED; Thu, 31 Mar 2022 21:53:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1648763624; bh=1YPzAg6KEd1+8m1rUGHvS4eDljvh1Mtdlp+ferumJv8=; h=Date:To:From:Subject:From; b=vMtCz2HraY9kyXL9DzD4yRYoU3IJRTD6r3vxFDVQhpRljandn5kNcbgzz4ykaJ1G0 HeTurRoYEjz9x0BsZd9ikduVPUOtA3AwoL/XJY8DxtZS2IUYDTtHEUhUzPkLfdGpfa +Fvv5rDv/GPOPaH4gXALZWuQ2WySNMwBewgAzQko= Date: Thu, 31 Mar 2022 14:53:42 -0700 To: mm-commits@vger.kernel.org, mingo@kernel.org, kirill.shutemov@linux.intel.com, jforbes@redhat.com, aquini@redhat.com, longman@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning.patch added to -mm tree Message-Id: <20220331215344.37963C340ED@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm/sparsemem: fix 'mem_section' will never be NULL gcc 12 warning has been added to the -mm tree. Its filename is mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Waiman Long Subject: mm/sparsemem: fix 'mem_section' will never be NULL gcc 12 warning 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 --- include/linux/mmzone.h | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) --- a/include/linux/mmzone.h~mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning +++ a/include/linux/mmzone.h @@ -1397,13 +1397,16 @@ static inline unsigned long *section_to_ 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 size_t mem_section_usage_size(void); _ Patches currently in -mm which might be from longman@redhat.com are mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning.patch mm-list_lru-fix-possible-race-in-memcg_reparent_list_lru_node.patch ipc-mqueue-use-get_tree_nodev-in-mqueue_get_tree.patch