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 X-Spam-Level: X-Spam-Status: No, score=-6.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF993C4338F for ; Wed, 18 Aug 2021 09:03:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B408261053 for ; Wed, 18 Aug 2021 09:03:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231529AbhHRJD7 (ORCPT ); Wed, 18 Aug 2021 05:03:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58300 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229780AbhHRJDx (ORCPT ); Wed, 18 Aug 2021 05:03:53 -0400 Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CCE75C061764 for ; Wed, 18 Aug 2021 02:03:18 -0700 (PDT) Received: by mail-pl1-x632.google.com with SMTP id w6so1369851plg.9 for ; Wed, 18 Aug 2021 02:03:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=Wi6GiW3siAeArZqvWLcz46sruMCMOkQL9Tx1MHP2F9M=; b=O6b9QEJX2A+BMP2t/Jopnb3uLzfw7MkxdgYGDPd8kXg7lj6i5rW4b1KQUD7duBp0NW ARZb6rSvwK8yUjjDtTmZ/No5b/N6TJNMpFMfjHQcB66xfWC5jxVfZdmVgg/rw4tb9D9m KTQ5SvRW25g7NfqelO4dYcMxQcfvJG7CIhrVQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=Wi6GiW3siAeArZqvWLcz46sruMCMOkQL9Tx1MHP2F9M=; b=cyycmAbUyP+MEhea6Q0qbMU1HkQu4kFkZr05PJMO75XyP5FwEaxoaGmB4/QbS5Yj4/ kQ2IQdr6BYm/8yGLMpLODAfyUr2UI0hja/01HEwIu891oVVh21ONeVC9bW7iMZtZ8Jlz 2usvP9AtGK5Kpx7CckQiWVQ7CRi0H4DKE20xq+dukLWcvCTN2clVFwXDoGvUpRM2qryY 1s6A/x/w+dv8cB8QzVa73/JchrSsnOFnU1/+3FJcASSUpOsABoPBclzycG9InxzaGnJi CUKyxN5RfhbK4IDM4YP1VYILDggKdEMuHC8yzSLRMUk+fOdEqGA56kpOMOSBA5GIs/PT 4JCQ== X-Gm-Message-State: AOAM530IErtFd6qR0SIEBaoJteHLOP/45YX8h/j1SiWxKp8KoUUyaTrF Vy4C5peRufnpGlAxWd1DCJk6yg== X-Google-Smtp-Source: ABdhPJwBy4P3b9ZHL/uuEc5QK3+QU7JmWq9RZXhEv09uSY9Rwkh8duMfsoih0ejFVq5RU4iOGkX0cA== X-Received: by 2002:a17:903:22cd:b0:12d:8876:eea7 with SMTP id y13-20020a17090322cd00b0012d8876eea7mr6462580plg.75.1629277398247; Wed, 18 Aug 2021 02:03:18 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id y13sm5730422pfq.147.2021.08.18.02.03.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Aug 2021 02:03:17 -0700 (PDT) Date: Wed, 18 Aug 2021 02:03:16 -0700 From: Kees Cook To: Vincent MAILHOL Cc: Wolfgang Grandegger , Marc Kleine-Budde , "David S. Miller" , Jakub Kicinski , Arunachalam Santhanam , linux-can , netdev , open list , linux-hardening@vger.kernel.org Subject: Re: [PATCH] can: etas_es58x: Replace 0-element raw_msg array Message-ID: <202108180159.5C1CEE70F@keescook> References: <20210818034010.800652-1-keescook@chromium.org> <202108172320.1540EC10C@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 18, 2021 at 04:55:20PM +0900, Vincent MAILHOL wrote: > At the end, the only goal of raw_msg[] is to have a tag pointing > to the beginning of the union. It would be virtually identical to > something like: > | u8 raw_msg[]; > | union { > | /* ... */ > | } __packed ; > > I had a look at your work and especially at your struct_group() macro. > Do you think it would make sense to introduce a union_group()? > > Result would look like: > > | union_group_attr(urb_msg, __packed, /* raw_msg renamed to urb_msg */ > | struct es58x_fd_tx_conf_msg tx_conf_msg; > | u8 tx_can_msg_buf[ES58X_FD_TX_BULK_MAX * ES58X_FD_CANFD_TX_LEN]; > | u8 rx_can_msg_buf[ES58X_FD_RX_BULK_MAX * ES58X_FD_CANFD_RX_LEN]; > | struct es58x_fd_echo_msg echo_msg[ES58X_FD_ECHO_BULK_MAX]; > | struct es58x_fd_rx_event_msg rx_event_msg; > | struct es58x_fd_tx_ack_msg tx_ack_msg; > | __le64 timestamp; > | __le32 rx_cmd_ret_le32; > | ); > > And I can then use urb_msg in place of the old raw_msg (might > need a bit of rework here and there but I can take care of it). > > This is the most pretty way I can think of to remove this zero length array. > Keeping the raw_msg[] but with another size seems odd to me. > > Or maybe I would be the only one using this feature in the full > tree? In that case, maybe it would make sense to keep the > union_group_attr() macro local to the etas_es58x driver? I actually ended up with something close to this idea, but more generalized for other cases in the kernel. There was a sane way to include a "real" flexible array in a union (or alone in a struct), so I've proposed this flex_array() helper: https://lore.kernel.org/lkml/20210818081118.1667663-2-keescook@chromium.org/ and then it's just a drop-in replacement for all the places that need this fixed, including etas_es58x: https://lore.kernel.org/lkml/20210818081118.1667663-3-keescook@chromium.org/#Z30drivers:net:can:usb:etas_es58x:es581_4.h Hopefully this will work out; I think it's as clean as we can get for now. :) -- Kees Cook