From patchwork Thu May 7 19:01:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 219664 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=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 2D447C38A24 for ; Thu, 7 May 2020 18:57:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 09E5920575 for ; Thu, 7 May 2020 18:57:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877830; bh=WOf9xpQ5HsvErqveasmOo+6FbaiSq7EMDBqA6Zuvr9g=; h=Date:From:To:Cc:Subject:List-ID:From; b=qEqHsoVtLgUGJcDHoVFK1RgAdIDK6kew7yhdDECBuXJaxdFE4SULL5bknXCgFtpVN lKmVB+tXG5ntRE57a9GctcXZB4X44vjm7Fs1gmHEUGGjCSnMxxpHRNXfODzD0SgWS6 45G8QYC9H1waaUQPuBZh7V79DKziAzh/16pJIato= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728110AbgEGS5I (ORCPT ); Thu, 7 May 2020 14:57:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:58496 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726320AbgEGS5I (ORCPT ); Thu, 7 May 2020 14:57:08 -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 1A9AF20575; Thu, 7 May 2020 18:57:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877827; bh=WOf9xpQ5HsvErqveasmOo+6FbaiSq7EMDBqA6Zuvr9g=; h=Date:From:To:Cc:Subject:From; b=CZVkXBlqK81ZHEkhF1UydIa0D9wZ9bRa9JmpvmtRjbh0+WYW04qHnCaqXuGcXvY3V 48pWDiywx9NuKbmQNtITowylWMtvROmmq+p6rcRmo3Ft8wmy0KxuX1q0YWPlwBrKQA jiIPE0lWR8D0TZuZJkz/+NzN+Es+QCp1xbf+vtz4= Date: Thu, 7 May 2020 14:01:33 -0500 From: "Gustavo A. R. Silva" To: "David S. Miller" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] net: atarilance: Replace zero-length array with flexible-array Message-ID: <20200507190133.GA15348@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@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/net/ethernet/amd/atarilance.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/ethernet/amd/atarilance.c b/drivers/net/ethernet/amd/atarilance.c index 4e36122609a3..961796abab35 100644 --- a/drivers/net/ethernet/amd/atarilance.c +++ b/drivers/net/ethernet/amd/atarilance.c @@ -156,7 +156,7 @@ struct lance_memory { struct lance_init_block init; struct lance_tx_head tx_head[TX_RING_SIZE]; struct lance_rx_head rx_head[RX_RING_SIZE]; - char packet_area[0]; /* packet data follow after the + char packet_area[]; /* packet data follow after the * init block and the ring * descriptors and are located * at runtime */