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 1F2FDC38A24 for ; Thu, 7 May 2020 18:39:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EA03020A8B for ; Thu, 7 May 2020 18:39:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588876772; bh=VeEp+7ElE8l0tzoN6UVq725ChaSk6ssE/a/96+hHjLQ=; h=Date:From:To:Cc:Subject:List-ID:From; b=lEhqRpeTh1MXvc3oA8rXHNW0eE/ker68/bUr/CexgP2Y/GgBSvsQeuA5N/EdoF2lt a62Fj+Omf7PQppT5HP8vUZr9b1YFRlGjPDVB+cZTJJz426KANNewh3qSpgcKsfDRov Y5Wtfq9e0DZHwFC7BTP4Nv+tTe7y1J+3Ge+FgRz4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728267AbgEGSjb (ORCPT ); Thu, 7 May 2020 14:39:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:42188 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726320AbgEGSja (ORCPT ); Thu, 7 May 2020 14:39:30 -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 01F37208E4; Thu, 7 May 2020 18:39:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588876770; bh=VeEp+7ElE8l0tzoN6UVq725ChaSk6ssE/a/96+hHjLQ=; h=Date:From:To:Cc:Subject:From; b=Oka4zgLyWhvs9qPh4nStDKAgEnONj2ECf/9F09hkV0Xao548k88iljJT1ngwc+hlE U7s/tIitE60gxPtkPxWqqoqUhrkqocDbfN/yU9A7otmD7UtALJmydj1BohZ+Qnvi1D rmj63SjbJBhNLxg0G5qBL1SKdI4ZBowWz+yc9siM= Date: Thu, 7 May 2020 13:43:56 -0500 From: "Gustavo A. R. Silva" To: John Johansen Cc: linux-kernel@vger.kernel.org Subject: [PATCH] apparmor: Replace zero-length array with flexible-array Message-ID: <20200507184356.GA13448@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 --- security/apparmor/apparmorfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c index 280741fc0f5f..299994ff9168 100644 --- a/security/apparmor/apparmorfs.c +++ b/security/apparmor/apparmorfs.c @@ -839,7 +839,7 @@ static ssize_t query_label(char *buf, size_t buf_len, struct multi_transaction { struct kref count; ssize_t size; - char data[0]; + char data[]; }; #define MULTI_TRANSACTION_LIMIT (PAGE_SIZE - sizeof(struct multi_transaction))