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=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 C5686C432BE for ; Fri, 30 Jul 2021 15:32:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF23860F4B for ; Fri, 30 Jul 2021 15:32:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239583AbhG3PcX (ORCPT ); Fri, 30 Jul 2021 11:32:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58046 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239514AbhG3PcW (ORCPT ); Fri, 30 Jul 2021 11:32:22 -0400 Received: from mail-lj1-x234.google.com (mail-lj1-x234.google.com [IPv6:2a00:1450:4864:20::234]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 51D8BC061765 for ; Fri, 30 Jul 2021 08:32:16 -0700 (PDT) Received: by mail-lj1-x234.google.com with SMTP id l17so12942914ljn.2 for ; Fri, 30 Jul 2021 08:32:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=cuMBivazXPSSSnLg5TVHL25KvD4e4AyXmAdQoyFf5fI=; b=V0takgq4CkvNar1Q60JxHbTt1cqvFsAT2Ql1xCcWDlliF/9fK1Tk6u2NKjLJFi2NsP OtAUbjW/Hk6YTr3ZTfouOa43d0DCv4/nxXOIFvMh2o9s/LUtXhmtgHgxqNBlfkoO+0Ox d1GAjEOyAM0plTITbZ2w6WFa49Z5MRcmaq85CbQLNYZrVs9T1wQ8UUGFYid/G6OviM1d OMFu6dCu79GrtbGkEZtfmLAS5L0sYxR0jmS86rEcpL2kD9pJaHk0tbVbZ7ZyxkbmW+U+ QcVQ4cI0n7yRxCSYVdO9PPaLX284Bky+u6/vpPnImSqzkgKcHLw7rJHQ0RyOSVMQVUfP ZxKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=cuMBivazXPSSSnLg5TVHL25KvD4e4AyXmAdQoyFf5fI=; b=mm+S5azCganGHhct/YeAwILZH29nmmFruFJCvKHUK+8oEkxPevkQZje5Y/4Ya9D8KF fhp7JFgzdWPGosJsmZpHfOFrzMpodLt4Tjoz2yvRt9ij0fWb00aFAap5KKot4X/XLCsd sNEGUefRYIVD4RsGlGB6ntSO5EkrR1ivw685laFnkCskyNdi2FONJnVubr6lvPTFZjfL NtuVOBnPO5AiI1na42iBYxrAVNAIY9oHfHkRdf97MLCHM6mi27pVHmTHgFbo7JUimH6U 6GDzEdCDZfkkyayhKTwYzJySgTk+Hx4OAOgIQ0DeeUOlWdwqIJZL+jcxf9xJA7Zarvoa wBXA== X-Gm-Message-State: AOAM532UkZIEG1poVyPQND4jfcDqbACxHbzMK5lYcUS+RmU9Y+v3EuRQ MtlIP/NE3avGlrthzdv+Ah2YAldf/NJ5YmY3xe9o7g== X-Google-Smtp-Source: ABdhPJzhoAUM4a6+aRW2w5iC66nC+BulVEtoEK+XmW3hkTpBTQktpdSzzUsKFLM2RILR3UqcvgdkDUL260mhYjHoyJw= X-Received: by 2002:a2e:a911:: with SMTP id j17mr2005145ljq.341.1627659134322; Fri, 30 Jul 2021 08:32:14 -0700 (PDT) MIME-Version: 1.0 References: <20210727205855.411487-1-keescook@chromium.org> <20210727205855.411487-49-keescook@chromium.org> <1cc74e5e-8d28-6da4-244e-861eac075ca2@acm.org> <202107291845.1E1528D@keescook> In-Reply-To: <202107291845.1E1528D@keescook> From: Nick Desaulniers Date: Fri, 30 Jul 2021 08:32:03 -0700 Message-ID: Subject: Re: [PATCH 48/64] drbd: Use struct_group() to zero algs To: Kees Cook Cc: Bart Van Assche , linux-hardening@vger.kernel.org, "Gustavo A. R. Silva" , Keith Packard , Greg Kroah-Hartman , Andrew Morton , linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-staging@lists.linux.dev, linux-block@vger.kernel.org, linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Thu, Jul 29, 2021 at 7:31 PM Kees Cook wrote: > > On Wed, Jul 28, 2021 at 02:45:55PM -0700, Bart Van Assche wrote: > > On 7/27/21 1:58 PM, Kees Cook wrote: > > > In preparation for FORTIFY_SOURCE performing compile-time and run-time > > > field bounds checking for memset(), avoid intentionally writing across > > > neighboring fields. > > > > > > Add a struct_group() for the algs so that memset() can correctly reason > > > about the size. > > > > > > Signed-off-by: Kees Cook > > > --- > > > drivers/block/drbd/drbd_main.c | 3 ++- > > > drivers/block/drbd/drbd_protocol.h | 6 ++++-- > > > drivers/block/drbd/drbd_receiver.c | 3 ++- > > > 3 files changed, 8 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c > > > index 55234a558e98..b824679cfcb2 100644 > > > --- a/drivers/block/drbd/drbd_main.c > > > +++ b/drivers/block/drbd/drbd_main.c > > > @@ -729,7 +729,8 @@ int drbd_send_sync_param(struct drbd_peer_device *peer_device) > > > cmd = apv >= 89 ? P_SYNC_PARAM89 : P_SYNC_PARAM; > > > /* initialize verify_alg and csums_alg */ > > > - memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX); > > > + BUILD_BUG_ON(sizeof(p->algs) != 2 * SHARED_SECRET_MAX); > > > + memset(&p->algs, 0, sizeof(p->algs)); > > > if (get_ldev(peer_device->device)) { > > > dc = rcu_dereference(peer_device->device->ldev->disk_conf); > > > diff --git a/drivers/block/drbd/drbd_protocol.h b/drivers/block/drbd/drbd_protocol.h > > > index dea59c92ecc1..a882b65ab5d2 100644 > > > --- a/drivers/block/drbd/drbd_protocol.h > > > +++ b/drivers/block/drbd/drbd_protocol.h > > > @@ -283,8 +283,10 @@ struct p_rs_param_89 { > > > struct p_rs_param_95 { > > > u32 resync_rate; > > > - char verify_alg[SHARED_SECRET_MAX]; > > > - char csums_alg[SHARED_SECRET_MAX]; > > > + struct_group(algs, > > > + char verify_alg[SHARED_SECRET_MAX]; > > > + char csums_alg[SHARED_SECRET_MAX]; > > > + ); > > > u32 c_plan_ahead; > > > u32 c_delay_target; > > > u32 c_fill_target; > > > diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c > > > index 1f740e42e457..6df2539e215b 100644 > > > --- a/drivers/block/drbd/drbd_receiver.c > > > +++ b/drivers/block/drbd/drbd_receiver.c > > > @@ -3921,7 +3921,8 @@ static int receive_SyncParam(struct drbd_connection *connection, struct packet_i > > > /* initialize verify_alg and csums_alg */ > > > p = pi->data; > > > - memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX); > > > + BUILD_BUG_ON(sizeof(p->algs) != 2 * SHARED_SECRET_MAX); > > > + memset(&p->algs, 0, sizeof(p->algs)); > > > > Using struct_group() introduces complexity. Has it been considered not to > > modify struct p_rs_param_95 and instead to use two memset() calls instead of > > one (one memset() call per member)? > > I went this direction because using two memset()s (or memcpy()s in other > patches) changes the machine code. It's not much of a change, but it > seems easier to justify "no binary changes" via the use of struct_group(). > > If splitting the memset() is preferred, I can totally do that instead. > :) I'm not sure that compilers can fold memsets of adjacent members. It might not matter, but you could wrap these members in a _named_ struct then simply use assignment for optimal codegen. -- Thanks, ~Nick Desaulniers