From patchwork Thu May 21 23:10:49 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: 11564173 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 BFC4A1392 for ; Thu, 21 May 2020 23:06:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A7B6F20825 for ; Thu, 21 May 2020 23:06:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590102365; bh=P1jeoOmkuQys8O/5KShp1h4j+v/r/jvzvMQiBaCGXUA=; h=Date:From:To:Cc:Subject:List-ID:From; b=xXgtDyKslebssNO+eHMKNSJ9zUa9ELMk50xe0mLJzl4KecYTnkXtk8mG0f3ctQiJG lNtMfOHwz14ywqzb1I0wdiiGYNhIeA9v2rHxgoFZ6omBiz42mB6e0tbMqpCj+ooTiX 3QeUSObOPgDPuH71gC2hvET7E1MsRAkxvqlKFQ7w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730740AbgEUXGB (ORCPT ); Thu, 21 May 2020 19:06:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:53146 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730041AbgEUXGB (ORCPT ); Thu, 21 May 2020 19:06:01 -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 BAF88207F9; Thu, 21 May 2020 23:05:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590102360; bh=P1jeoOmkuQys8O/5KShp1h4j+v/r/jvzvMQiBaCGXUA=; h=Date:From:To:Cc:Subject:From; b=kjPULzZ9+vdGSNsCk+ICfxYRoVBIOI+MIGmNveAC203FdJXa8MM2KqRQwPrsB5WTP Hd1WLCThXNMhcz0Aa7ps91f0RAECthDDyO7Q4bHQ9aOLc8gK8aYdifRf1Q3d939mHf 1VFgtiIQkJ85EL12T+jWB/tPAznRNsrvIn2eX2io= Date: Thu, 21 May 2020 18:10:49 -0500 From: "Gustavo A. R. Silva" To: Mimi Zohar , Dmitry Kasatkin , James Morris , "Serge E. Hallyn" Cc: linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] security: integrity: Replace zero-length array with flexible-array member Message-ID: <20200521231049.GA28765@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 +- security/integrity/integrity.h | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index 02796473238b6..3ec963ff3bc19 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -100,7 +100,7 @@ struct ima_template_entry { struct tpm_digest *digests; 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 { diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h index 298b73794d8b1..16c1894c29bb0 100644 --- a/security/integrity/integrity.h +++ b/security/integrity/integrity.h @@ -107,7 +107,7 @@ struct ima_digest_data { } ng; u8 data[2]; } xattr; - u8 digest[0]; + u8 digest[]; } __packed; /* @@ -119,7 +119,7 @@ struct signature_v2_hdr { uint8_t hash_algo; /* Digest algorithm [enum hash_algo] */ __be32 keyid; /* IMA key identifier - not X509/PGP specific */ __be16 sig_size; /* signature size */ - uint8_t sig[0]; /* signature payload */ + uint8_t sig[]; /* signature payload */ } __packed; /* integrity data associated with an inode */