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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,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 5E6E9C38A2A for ; Thu, 7 May 2020 19:00:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BD562173E for ; Thu, 7 May 2020 19:00:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588878028; bh=R5UAo0X2wUIkcPu2bAHYaMr9+zALVRcFirsDyRQuvAA=; h=Date:From:To:Cc:Subject:List-ID:From; b=eK8sukP9kkFw9KEMzcKj9r5Cfnp3yZvrZipvQaaihnyzSevjylya6jD6rSZnV5E68 n08YfCTXxbevUJntpC09NJI6YBDSt7IrtAinId71Bi5OBgAVvtzqXR797kRXGnNlwN iWK/reS45d9sLiqLLgDSydCdPxDlh1YA8SVEa2cg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727799AbgEGTA1 (ORCPT ); Thu, 7 May 2020 15:00:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:60418 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726320AbgEGTA0 (ORCPT ); Thu, 7 May 2020 15:00:26 -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 672612083B; Thu, 7 May 2020 19:00:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588878025; bh=R5UAo0X2wUIkcPu2bAHYaMr9+zALVRcFirsDyRQuvAA=; h=Date:From:To:Cc:Subject:From; b=qn6cRKwYPaaWKY02MVF/8V8omrkz4xrVRvn2mw1GgLEW7gI9lUssG9pLlKKk2VhXv 5lnk1EO5WSRyv2MHzvSJVPLTRNEPsu7qB/FSmbaEWWBcjh6O7k+szJmk8I8vkNwwhZ wlNH83fi8M3q2rmCoHlvy3jMpsr/dYfz/ln8iMIc= Date: Thu, 7 May 2020 14:04:52 -0500 From: "Gustavo A. R. Silva" To: Keith Busch , Jens Axboe , Christoph Hellwig , Sagi Grimberg Cc: linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH] lightnvm: Replace zero-length array with flexible-array Message-ID: <20200507190452.GA15449@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 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/nvme/host/lightnvm.c | 2 +- include/linux/nvme.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c index ec46693f6b64..3002bf972c6b 100644 --- a/drivers/nvme/host/lightnvm.c +++ b/drivers/nvme/host/lightnvm.c @@ -171,7 +171,7 @@ struct nvme_nvm_bb_tbl { __le32 tdresv; __le32 thresv; __le32 rsvd2[8]; - __u8 blk[0]; + __u8 blk[]; }; struct nvme_nvm_id20_addrf { diff --git a/include/linux/nvme.h b/include/linux/nvme.h index 3d5189f46cb1..6ee80a44ed4f 100644 --- a/include/linux/nvme.h +++ b/include/linux/nvme.h @@ -1177,7 +1177,7 @@ struct nvmf_disc_rsp_page_hdr { __le64 numrec; __le16 recfmt; __u8 resv14[1006]; - struct nvmf_disc_rsp_page_entry entries[0]; + struct nvmf_disc_rsp_page_entry entries[]; }; enum {