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=-10.2 required=3.0 tests=FAKE_REPLY_C, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 E286BC433E0 for ; Fri, 15 May 2020 06:08:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BCBBD20760 for ; Fri, 15 May 2020 06:08:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726184AbgEOGIW (ORCPT ); Fri, 15 May 2020 02:08:22 -0400 Received: from helcar.hmeau.com ([216.24.177.18]:34268 "EHLO fornost.hmeau.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726137AbgEOGIW (ORCPT ); Fri, 15 May 2020 02:08:22 -0400 Received: from gwarestrin.arnor.me.apana.org.au ([192.168.0.7]) by fornost.hmeau.com with smtp (Exim 4.89 #2 (Debian)) id 1jZTVs-0007Bi-Ew; Fri, 15 May 2020 16:08:05 +1000 Received: by gwarestrin.arnor.me.apana.org.au (sSMTP sendmail emulation); Fri, 15 May 2020 16:08:04 +1000 Date: Fri, 15 May 2020 16:08:04 +1000 From: Herbert Xu To: "Gustavo A. R. Silva" Cc: ayush.sawal@chelsio.com, vinay.yadav@chelsio.com, rohitm@chelsio.com, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] crypto: Replace zero-length array with flexible-array Message-ID: <20200515060804.GA10825@gondor.apana.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200507185145.GA14096@embeddedor> X-Newsgroups: apana.lists.os.linux.cryptoapi,apana.lists.os.linux.kernel User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org Gustavo A. R. Silva wrote: > The current codebase makes use of the zero-length array language > extension to the C90 standard, but the preferred mechanism to declare > variable-length types such as these ones is a flexible array member[1][2], > introduced in C99: > > struct foo { > int stuff; > struct boo array[]; > }; > > By making use of the mechanism above, we will get a compiler warning > in case the flexible array does not occur last in the structure, which > will help us prevent some kind of undefined behavior bugs from being > inadvertently introduced[3] to the codebase from now on. > > Also, notice that, dynamic memory allocations won't be affected by > this change: > > "Flexible array members have incomplete type, and so the sizeof operator > may not be applied. As a quirk of the original implementation of > zero-length arrays, sizeof evaluates to zero."[1] > > sizeof(flexible-array-member) triggers a warning because flexible array > members have incomplete type[1]. There are some instances of code in > which the sizeof operator is being incorrectly/erroneously applied to > zero-length arrays and the result is zero. Such instances may be hiding > some bugs. So, this work (flexible-array member conversions) will also > help to get completely rid of those sorts of issues. > > This issue was found with the help of Coccinelle. > > [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html > [2] https://github.com/KSPP/linux/issues/21 > [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") > > Signed-off-by: Gustavo A. R. Silva > --- > drivers/crypto/chelsio/chcr_crypto.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) Please resend via netdev. Thanks. -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt