From patchwork Thu May 7 19:02:10 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: 11534747 X-Patchwork-Delegate: kvalo@adurom.com Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D6C2F14B4 for ; Thu, 7 May 2020 18:57:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BFDEE2184D for ; Thu, 7 May 2020 18:57:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877877; bh=9XCa7JR8FEKWus1Qn+mqDl5wGlHwBasdYcxvlyL3UIE=; h=Date:From:To:Cc:Subject:List-ID:From; b=IbKAoCi1emD+Pb+uBQR8Asv2FoQROYUPVnOdTxQDr7eORDWSjvrWMMaTf94y2IuHK 3DauNKHPw0SvaU7KdpiznfHGewio6+FO1kMtg1Q6R6n+4/+gM274hYSVaEdDYait3P xpsHhZYhFxwbiz/+yJKwkRmWNs5Aj2RPJtUoVM0I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727930AbgEGS5o (ORCPT ); Thu, 7 May 2020 14:57:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:59018 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726515AbgEGS5o (ORCPT ); Thu, 7 May 2020 14:57:44 -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 32EAE20575; Thu, 7 May 2020 18:57:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877863; bh=9XCa7JR8FEKWus1Qn+mqDl5wGlHwBasdYcxvlyL3UIE=; h=Date:From:To:Cc:Subject:From; b=cLWoOWnWSjpR3Du9o2F3Qd82FQmLI/66sVQVdLxm/bSd9nVkav9uvOsbnuU6GHk0z AF1Ah4JK+jKnhfwg915hBJM18wQtcYCXuNBVrgNqwyv5ZYI2YbxVHOaDOBdpzkHmsF UdYkx8KJjFYUHvoWcoUzis4TTuaXjWsYQNTP6qC4= Date: Thu, 7 May 2020 14:02:10 -0500 From: "Gustavo A. R. Silva" To: Kalle Valo Cc: linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] prism54: Replace zero-length array with flexible-array Message-ID: <20200507190210.GA15375@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@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/intersil/prism54/isl_oid.h | 8 ++++---- drivers/net/wireless/intersil/prism54/islpci_mgt.h | 2 +- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/net/wireless/intersil/prism54/isl_oid.h b/drivers/net/wireless/intersil/prism54/isl_oid.h index 5441c1f9f2fc..1afc2ccf94ca 100644 --- a/drivers/net/wireless/intersil/prism54/isl_oid.h +++ b/drivers/net/wireless/intersil/prism54/isl_oid.h @@ -37,7 +37,7 @@ struct obj_mlmeex { u16 state; u16 code; u16 size; - u8 data[0]; + u8 data[]; } __packed; struct obj_buffer { @@ -68,12 +68,12 @@ struct obj_bss { struct obj_bsslist { u32 nr; - struct obj_bss bsslist[0]; + struct obj_bss bsslist[]; } __packed; struct obj_frequencies { u16 nr; - u16 mhz[0]; + u16 mhz[]; } __packed; struct obj_attachment { @@ -81,7 +81,7 @@ struct obj_attachment { char reserved; short id; short size; - char data[0]; + char data[]; } __packed; /* diff --git a/drivers/net/wireless/intersil/prism54/islpci_mgt.h b/drivers/net/wireless/intersil/prism54/islpci_mgt.h index d6bbbac46b4a..1f87d0aea60c 100644 --- a/drivers/net/wireless/intersil/prism54/islpci_mgt.h +++ b/drivers/net/wireless/intersil/prism54/islpci_mgt.h @@ -99,7 +99,7 @@ struct islpci_mgmtframe { pimfor_header_t *header; /* payload header, points into buf */ void *data; /* payload ex header, points into buf */ struct work_struct ws; /* argument for schedule_work() */ - char buf[0]; /* fragment buffer */ + char buf[]; /* fragment buffer */ }; int