From patchwork Thu May 7 18:53:51 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: 11534701 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 C1C6115AB for ; Thu, 7 May 2020 18:49:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA3FA24959 for ; Thu, 7 May 2020 18:49:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877366; bh=pk7QrAL3NDjeA4BB8U07kjEUUtfctxSRQ394nM277v4=; h=Date:From:To:Cc:Subject:List-ID:From; b=a5BW0pMh3Abdiz7g2puY7RY6kzV7RX8E6nWWTjWNh1MsXQyqR+Yu/+47MMsVguxUJ xXUTzWLHZAjNeYeNStGdylExFKey67dCmoMMN7VSbVtBR0Gpie2m2OhGRvTLsbOxae g21+rmS7t6Rxp+oYEQxn9oLpsQrv90z/VdIhr/5I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728395AbgEGSt0 (ORCPT ); Thu, 7 May 2020 14:49:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:50732 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728097AbgEGStZ (ORCPT ); Thu, 7 May 2020 14:49:25 -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 0943124957; Thu, 7 May 2020 18:49:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877365; bh=pk7QrAL3NDjeA4BB8U07kjEUUtfctxSRQ394nM277v4=; h=Date:From:To:Cc:Subject:From; b=ewFUKtOokui8KqvgXxgQbs1XcpdPapWxul2Zw+SPUBSPM2TvMrwTGaDW6+kek18ka khLJOC525uEUctcdf8bKfyhasQTJbEx3L70DCvIEMkBkdyc+QyCzuhl45XzC9igQvQ VnELWJfggr5xFYGVJEg14g8TdtP6OPk9dbZ4UX2E= Date: Thu, 7 May 2020 13:53:51 -0500 From: "Gustavo A. R. Silva" To: Mimi Zohar , Dmitry Kasatkin Cc: linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] ima: Replace zero-length array with flexible-array Message-ID: <20200507185351.GA14519@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@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/integrity/ima/ima.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index 64317d95363e..da4246ee7e35 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -95,7 +95,7 @@ struct ima_template_entry { u8 digest[TPM_DIGEST_SIZE]; /* sha1 or md5 measurement hash */ struct ima_template_desc *template_desc; /* template descriptor */ u32 template_data_len; - struct ima_field_data template_data[0]; /* template related data */ + struct ima_field_data template_data[]; /* template related data */ }; struct ima_queue_entry {