From patchwork Thu May 7 18:57:04 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: 11534717 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 7F96414B4 for ; Thu, 7 May 2020 18:52:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 683052495D for ; Thu, 7 May 2020 18:52:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877559; bh=3p7eu1MK3/DsGvUUePG2CQuwCI8FRfOqNY3jSgtHysA=; h=Date:From:To:Cc:Subject:List-ID:From; b=oHx9ohnWkSwxFAaAY5gzgS2jdoymeoPuMZK6eB4Tlu1k4Cy+o7E5vHEC5YrzXsrZh RNFto79Tn7vcM0dLuiZIKdJ6RLfQf90+sMs7JRrA0H/Wd6oWSXdqFZ87a/P06fl6nY A9/7BxuWy7aTkxePA90Q8IAe6ZQBu1xZPOkPqtiw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727799AbgEGSwj (ORCPT ); Thu, 7 May 2020 14:52:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:53434 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726598AbgEGSwi (ORCPT ); Thu, 7 May 2020 14:52:38 -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 CDEB62495D; Thu, 7 May 2020 18:52:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877558; bh=3p7eu1MK3/DsGvUUePG2CQuwCI8FRfOqNY3jSgtHysA=; h=Date:From:To:Cc:Subject:From; b=zB00JXfY5N8MCu9LU/I8NuwjUD5M9q/ClnQmv+hVQlVvpsXrkVTu3m56rngM3C+n9 Go00HNUmFc1Vkx/dki3yRfaduBm2NW11l74aOfqScy+rrRBylrS/cWl15Ebsj1aPR6 OrghsOeoKArBE2ljeAIM/cWfp/6EDDLxNGtUNN/I= Date: Thu, 7 May 2020 13:57:04 -0500 From: "Gustavo A. R. Silva" To: Mimi Zohar Cc: linux-integrity@vger.kernel.org, keyrings@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] encrypted-keys: Replace zero-length array with flexible-array Message-ID: <20200507185704.GA14874@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: keyrings-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: keyrings@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 --- include/keys/encrypted-type.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/keys/encrypted-type.h b/include/keys/encrypted-type.h index 9e9ccb20d586..38afb341c3f2 100644 --- a/include/keys/encrypted-type.h +++ b/include/keys/encrypted-type.h @@ -27,7 +27,7 @@ struct encrypted_key_payload { unsigned short payload_datalen; /* payload data length */ unsigned short encrypted_key_format; /* encrypted key format */ u8 *decrypted_data; /* decrypted data */ - u8 payload_data[0]; /* payload data + datablob + hmac */ + u8 payload_data[]; /* payload data + datablob + hmac */ }; extern struct key_type key_type_encrypted;