From patchwork Thu May 7 19:06:38 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: 11534757 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 DF145159A for ; Thu, 7 May 2020 19:02:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C75262173E for ; Thu, 7 May 2020 19:02:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588878133; bh=1BaK2d/28Q3HiRySzkjK8VA6eqj1T7RCpk6P2tPRcUQ=; h=Date:From:To:Cc:Subject:List-ID:From; b=kGmzf97Zd7U+FQqPmfI3m+rd2bBJw64zXqf4m/IX7yXez5XVLmG3v4eqtJGCsousW U943cXpQb9g/L+1LjVOLqShwRfdCFHoovy6BTRLp5ojGMQQVnE7r8Sqk99HdXT4OY2 uY1qlKc8gtTVjL6GvlDwrytJnnphDdV62ElD8rkw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728045AbgEGTCN (ORCPT ); Thu, 7 May 2020 15:02:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:33280 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726926AbgEGTCM (ORCPT ); Thu, 7 May 2020 15:02:12 -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 04D4F2083B; Thu, 7 May 2020 19:02:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588878132; bh=1BaK2d/28Q3HiRySzkjK8VA6eqj1T7RCpk6P2tPRcUQ=; h=Date:From:To:Cc:Subject:From; b=SjV2+HqlI/Oyuk1tKqHzIVyfvzIIC0ng2W75q3QOaNO8CdboTX8sTZAFnr7y1vpd8 DGxg8REQrOFAuld69/Gt+037N7+iFJXTvLQoRy/hJ9ipynYwbnItpXmhMPCM3dde2Y QlKSMQeEErUXj3kJvXWdOw/mCb9O9+0nIYSllaCk= Date: Thu, 7 May 2020 14:06:38 -0500 From: "Gustavo A. R. Silva" To: "Rafael J. Wysocki" Cc: linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] PNPBIOS: Replace zero-length array with flexible-array Message-ID: <20200507190638.GA15700@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@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/pnp/pnpbios/pnpbios.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/pnp/pnpbios/pnpbios.h b/drivers/pnp/pnpbios/pnpbios.h index 37acb8378f39..2ce739ff9c1a 100644 --- a/drivers/pnp/pnpbios/pnpbios.h +++ b/drivers/pnp/pnpbios/pnpbios.h @@ -107,7 +107,7 @@ struct pnp_bios_node { __u32 eisa_id; __u8 type_code[3]; __u16 flags; - __u8 data[0]; + __u8 data[]; }; #pragma pack()