From patchwork Thu Mar 19 22:23:52 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: 210519 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=-13.1 required=3.0 tests=DKIM_INVALID, DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 148D2C4332B for ; Thu, 19 Mar 2020 23:09:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D70D02076C for ; Thu, 19 Mar 2020 23:09:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=embeddedor.com header.i=@embeddedor.com header.b="LBBXdvcP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727237AbgCSXJP (ORCPT ); Thu, 19 Mar 2020 19:09:15 -0400 Received: from gateway20.websitewelcome.com ([192.185.67.41]:11978 "EHLO gateway20.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726867AbgCSXJP (ORCPT ); Thu, 19 Mar 2020 19:09:15 -0400 X-Greylist: delayed 1502 seconds by postgrey-1.27 at vger.kernel.org; Thu, 19 Mar 2020 19:09:14 EDT Received: from cm12.websitewelcome.com (cm12.websitewelcome.com [100.42.49.8]) by gateway20.websitewelcome.com (Postfix) with ESMTP id 23401400C81CF for ; Thu, 19 Mar 2020 16:08:25 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id F3Zxj0BW51s2xF3ZyjiYjH; Thu, 19 Mar 2020 17:23:54 -0500 X-Authority-Reason: nr=8 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=embeddedor.com; s=default; h=Content-Type:MIME-Version:Message-ID:Subject: Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=6URqdS67bk0WU5yZN4/DlVoCb44PpZDm7Vl22nZSfqw=; b=LBBXdvcPHn6gf+mMZhQkYAC9xC vGwDbqJPNc7Ukn8xPPYLMkkpdDpUT0CRoBLHfjW3opok/8ZoNsOQCA8D0E8WKVQuNyj2uwfu1+uKm sONHDJg9Al6UwwLaXCRaunJnH2L0tN+WjJ+bs6cEjOpQFh2rEp8l2hqvaJcPk+0YoBaG0IX77Ylv9 OuMUmGbFo0o5zyjxH4/0p0oqLvkNLxuSPeHL0WYubFV32xQrqTTYmdBO3FFJiUcSQxkmFhPXTlJk1 /59X03wbcGPVVUB1nXGfbGUfA1pfpUB6gLk0x7JN45SYE7O6fDOkS2Hgvl8vfUqAKRD7h+Gz+3lSh hLEIfV5A==; Received: from cablelink-189-218-116-241.hosts.intercable.net ([189.218.116.241]:53894 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1jF3Zw-0024Kc-Fd; Thu, 19 Mar 2020 17:23:52 -0500 Date: Thu, 19 Mar 2020 17:23:52 -0500 From: "Gustavo A. R. Silva" To: Hans Verkuil , Mauro Carvalho Chehab Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] media: usb: pwc: pwc.h: Replace zero-length array with flexible-array member Message-ID: <20200319222352.GA19476@embeddedor.com> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 189.218.116.241 X-Source-L: No X-Exim-ID: 1jF3Zw-0024Kc-Fd X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: cablelink-189-218-116-241.hosts.intercable.net (embeddedor) [189.218.116.241]:53894 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 17 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@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] 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/media/usb/pwc/pwc.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/media/usb/pwc/pwc.h b/drivers/media/usb/pwc/pwc.h index 3362962d0d00..b02a3c7b7742 100644 --- a/drivers/media/usb/pwc/pwc.h +++ b/drivers/media/usb/pwc/pwc.h @@ -193,7 +193,7 @@ struct pwc_raw_frame { decompressor) */ __u8 cmd[4]; /* the four byte of the command (in case of nala, only the first 3 bytes is filled) */ - __u8 rawframe[0]; /* frame_size = H / 4 * vbandlength */ + __u8 rawframe[]; /* frame_size = H / 4 * vbandlength */ } __packed; /* intermediate buffers with raw data from the USB cam */