From patchwork Thu May 7 15:19:21 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: 219670 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 E4913C38A24 for ; Thu, 7 May 2020 15:14:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C1DE52083B for ; Thu, 7 May 2020 15:14:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588864499; bh=nH4zzLyFJaaR6EBGr6MwECFJ0OIX3tGLz6Ht3UbWkZM=; h=Date:From:To:Cc:Subject:List-ID:From; b=wPeHlSbjMlUdZEwobNyWmXGU5NGp0AEy9QIBcJHym4rjy085oZVuYLLOEKR8hcN91 f2PbOFXqFqYOKXgrT1/KXzg7viuS1ROdZiwQHpafj/g/M/Xl809li8vPRMA6Sn1YBv 6IO9bc+iOgHLybSWWnlynpnRJfQNCWyEo6cY40XU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726641AbgEGPO4 (ORCPT ); Thu, 7 May 2020 11:14:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:43302 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725914AbgEGPO4 (ORCPT ); Thu, 7 May 2020 11:14:56 -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 6FEBE207DD; Thu, 7 May 2020 15:14:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588864496; bh=nH4zzLyFJaaR6EBGr6MwECFJ0OIX3tGLz6Ht3UbWkZM=; h=Date:From:To:Cc:Subject:From; b=P/qI5XcxnpOU2JlzciA5QWZCZGmLZfddp8qb5bxXx45rDzjJdI2SqlGqYARDzuB84 TnO5gSmseGqu/btra6/WZaf7T3sS1E1uKVzKPJOzReH3MiUYqUUkXonvPEgfpQzHoh 1Zn0pmhSYAXfa6as0z/2b2XL/DF+K29mcfG4Pofo= Date: Thu, 7 May 2020 10:19:21 -0500 From: "Gustavo A. R. Silva" To: Christian Lamparter , Kalle Valo , "David S. Miller" Cc: linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] carl9170: Replace zero-length array with flexible-array Message-ID: <20200507151921.GA5083@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/wireless/ath/carl9170/fwcmd.h | 2 +- drivers/net/wireless/ath/carl9170/hw.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/wireless/ath/carl9170/fwcmd.h b/drivers/net/wireless/ath/carl9170/fwcmd.h index ea1d80f9a50e..56999a3b9d3b 100644 --- a/drivers/net/wireless/ath/carl9170/fwcmd.h +++ b/drivers/net/wireless/ath/carl9170/fwcmd.h @@ -127,7 +127,7 @@ struct carl9170_write_reg { struct carl9170_write_reg_byte { __le32 addr; __le32 count; - u8 val[0]; + u8 val[]; } __packed; #define CARL9170FW_PHY_HT_ENABLE 0x4 diff --git a/drivers/net/wireless/ath/carl9170/hw.h b/drivers/net/wireless/ath/carl9170/hw.h index 08e0ae9c5836..555ad4975970 100644 --- a/drivers/net/wireless/ath/carl9170/hw.h +++ b/drivers/net/wireless/ath/carl9170/hw.h @@ -851,7 +851,7 @@ struct ar9170_stream { __le16 length; __le16 tag; - u8 payload[0]; + u8 payload[]; } __packed __aligned(4); #define AR9170_STREAM_LEN 4