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 1515CCCA486 for ; Mon, 27 Jun 2022 18:38:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240388AbiF0Si0 (ORCPT ); Mon, 27 Jun 2022 14:38:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37490 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240436AbiF0SiC (ORCPT ); Mon, 27 Jun 2022 14:38:02 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9128FC34; Mon, 27 Jun 2022 11:35:20 -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 ams.source.kernel.org (Postfix) with ESMTPS id 5B84EB81A31; Mon, 27 Jun 2022 18:35:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 43D52C3411D; Mon, 27 Jun 2022 18:35:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1656354918; bh=lSduwLf0URPGJXhzE2uMPDSka0BN2NuObX6s6wiVjLw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=V1wgnhWIBSxTWZs7oVLQcgu6ow7j/nvOHPvXzsT1Nn9X7hdwGhqh7NAL8uHaamcIf IY07sAxOhUQqndCnsaxA3ScC1kTdg2Yn9hsnKIlxq8rxFKlV7RaY+NRmyVh3m75Tb8 ZpcqX4hfVCDBy0N1EVQnXiwwX9rIvnnkMDcCS04gZPnAV3H3k5TZVX9FzOMlpLx209 8O1zovzb/AU8MtbMYOdG7MyCPnmJKw+tFasJC0wEQpVPIKC5aCfVMO84EEc2E/4TTl 9dxSDJTazopgz1hOdfhMFc0UNVAF149+GJwdJJ2/y5zxk6J7RR9WnMOk8pk02PIKf/ G0d/RZr8PVXzA== Date: Mon, 27 Jun 2022 20:35:13 +0200 From: "Gustavo A. R. Silva" To: Daniel Borkmann Cc: Kees Cook , linux-kernel@vger.kernel.org, x86@kernel.org, dm-devel@redhat.com, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-can@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux1394-devel@lists.sourceforge.net, io-uring@vger.kernel.org, lvs-devel@vger.kernel.org, linux-mtd@lists.infradead.org, kasan-dev@googlegroups.com, linux-mmc@vger.kernel.org, nvdimm@lists.linux.dev, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, linux-perf-users@vger.kernel.org, linux-raid@vger.kernel.org, linux-sctp@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-usb@vger.kernel.org, virtualization@lists.linux-foundation.org, v9fs-developer@lists.sourceforge.net, linux-rdma@vger.kernel.org, alsa-devel@alsa-project.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH][next] treewide: uapi: Replace zero-length arrays with flexible-array members Message-ID: <20220627183513.GA137875@embeddedor> References: <20220627180432.GA136081@embeddedor> <6bc1e94c-ce1d-a074-7d0c-8dbe6ce22637@iogearbox.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <6bc1e94c-ce1d-a074-7d0c-8dbe6ce22637@iogearbox.net> Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Jun 27, 2022 at 08:27:37PM +0200, Daniel Borkmann wrote: > On 6/27/22 8:04 PM, Gustavo A. R. Silva wrote: > > There is a regular need in the kernel to provide a way to declare > > having a dynamically sized set of trailing elements in a structure. > > Kernel code should always use “flexible array members”[1] for these > > cases. The older style of one-element or zero-length arrays should > > no longer be used[2]. > > > > This code was transformed with the help of Coccinelle: > > (linux-5.19-rc2$ spatch --jobs $(getconf _NPROCESSORS_ONLN) --sp-file script.cocci --include-headers --dir . > output.patch) > > > > @@ > > identifier S, member, array; > > type T1, T2; > > @@ > > > > struct S { > > ... > > T1 member; > > T2 array[ > > - 0 > > ]; > > }; > > > > -fstrict-flex-arrays=3 is coming and we need to land these changes > > to prevent issues like these in the short future: > > > > ../fs/minix/dir.c:337:3: warning: 'strcpy' will always overflow; destination buffer has size 0, > > but the source string has length 2 (including NUL byte) [-Wfortify-source] > > strcpy(de3->name, "."); > > ^ > > > > Since these are all [0] to [] changes, the risk to UAPI is nearly zero. If > > this breaks anything, we can use a union with a new member name. > > > > [1] https://en.wikipedia.org/wiki/Flexible_array_member > > [2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays > > > > Link: https://github.com/KSPP/linux/issues/78 > > Build-tested-by: https://lore.kernel.org/lkml/62b675ec.wKX6AOZ6cbE71vtF%25lkp@intel.com/ > > Signed-off-by: Gustavo A. R. Silva > > --- > > Hi all! > > > > JFYI: I'm adding this to my -next tree. :) > > Fyi, this breaks BPF CI: Thanks for the report! It seems the 0-day robot didn't catch that one. I'll fix it up right away. :) -- Gustavo > > https://github.com/kernel-patches/bpf/runs/7078719372?check_suite_focus=true > > [...] > progs/map_ptr_kern.c:314:26: error: field 'trie_key' with variable sized type 'struct bpf_lpm_trie_key' not at the end of a struct or class is a GNU extension [-Werror,-Wgnu-variable-sized-type-not-at-end] > struct bpf_lpm_trie_key trie_key; > ^ > 1 error generated. > make: *** [Makefile:519: /tmp/runner/work/bpf/bpf/tools/testing/selftests/bpf/map_ptr_kern.o] Error 1 > make: *** Waiting for unfinished jobs.... > Error: Process completed with exit code 2.