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=-13.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 1DFC9C433DF for ; Thu, 21 May 2020 18:27:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F18E020826 for ; Thu, 21 May 2020 18:27:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590085668; bh=/WDW8VQf6iHXjI83NrrhTGfMoMsExmF4WWAKY8AsnD4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=hkPMaoRbCZ8zn+jydw2W+eiE0w+pUk1vtJhF0VP9DjdwW5okbMeEX/OcwVKC3jlzt a8lNbFFIT94FlxpRKFEJ8S99iEUnc1atpk8Jdghsu1pRkX7Qo4vAJQpGKzbBt9PjNy gpIDXlTjwqgEXWNQYnK0Q0jgemRmL5EwDxxXxpdU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729518AbgEUS1r (ORCPT ); Thu, 21 May 2020 14:27:47 -0400 Received: from mail.kernel.org ([198.145.29.99]:38628 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728240AbgEUS1q (ORCPT ); Thu, 21 May 2020 14:27:46 -0400 Received: from embeddedor (unknown [189.207.59.248]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DCBD720814; Thu, 21 May 2020 18:27:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590085666; bh=/WDW8VQf6iHXjI83NrrhTGfMoMsExmF4WWAKY8AsnD4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=eqzbcY7HsMUAYzkWVdfcRaT91gC/TZyEUicnStmo+ommIAhbivnvn8bxVE+UpaB/C IqB9zXAduOKiblcU/15eO8iaPW16NseBHN2F5rub4EE4m3fMeIYXTJqRfZB1DC0oFO qg21wdU6b32Qb0G4zPbANPByPYNE36HWCp8nIqI0= Date: Thu, 21 May 2020 13:32:35 -0500 From: "Gustavo A. R. Silva" To: Peter Jones , Konrad Rzeszutek Wilk Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] ibft: Replace zero-length array with flexible-array Message-ID: <20200521183235.GA29907@embeddedor> References: <20200507185544.GA14695@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200507185544.GA14695@embeddedor> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, Friendly ping: who can take this? Thanks -- Gustavo On Thu, May 07, 2020 at 01:55:44PM -0500, 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/firmware/iscsi_ibft.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/firmware/iscsi_ibft.c b/drivers/firmware/iscsi_ibft.c > index 96758b71a8db..7127a04bca19 100644 > --- a/drivers/firmware/iscsi_ibft.c > +++ b/drivers/firmware/iscsi_ibft.c > @@ -104,7 +104,7 @@ struct ibft_control { > u16 tgt0_off; > u16 nic1_off; > u16 tgt1_off; > - u16 expansion[0]; > + u16 expansion[]; > } __attribute__((__packed__)); > > struct ibft_initiator { >