From patchwork Thu Jan 16 22:03:27 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: 11337895 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 9FD22109A for ; Thu, 16 Jan 2020 22:49:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7E7262075B for ; Thu, 16 Jan 2020 22:49:41 +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="aWzpkYr+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387529AbgAPWtl (ORCPT ); Thu, 16 Jan 2020 17:49:41 -0500 Received: from gateway33.websitewelcome.com ([192.185.146.87]:18058 "EHLO gateway33.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729261AbgAPWtk (ORCPT ); Thu, 16 Jan 2020 17:49:40 -0500 X-Greylist: delayed 1500 seconds by postgrey-1.27 at vger.kernel.org; Thu, 16 Jan 2020 17:49:39 EST Received: from cm16.websitewelcome.com (cm16.websitewelcome.com [100.42.49.19]) by gateway33.websitewelcome.com (Postfix) with ESMTP id 9D5E121D7EF6 for ; Thu, 16 Jan 2020 16:03:29 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id sDEfiqzuo32AdsDEfi1eh9; Thu, 16 Jan 2020 16:03:29 -0600 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=lJqbOVGeD356I6fIe5iirDZBONX68UGjE9KZh7u5oGg=; b=aWzpkYr+XHoNFKlaSNzO+UXLZZ fuXnIZFQyXXrqcldKm/2ji1V6SAct69fFyXrBXeg7DVIefdRIQICEGlgT808cM5xUVN9B9jBvmfrP PVpJxi5Q7VK/lJ9YvgzhA8U3n/K/J3wgIpFHTSo/GDamYhIFLe+2qz5OJIgoauc2/IskXvvyxsN6H N4B9Ulm2locWbjIebP7r4PEqfdXrlRhdE8CpnJhIt9CihJjJY0mVxRXL9LUlKq2z6Y2P1O3j4SDPf 8ZLE35/7SbDuXJ9c4EYXbvOL3FlwQlFHyNmN4D9vqWgIvXfKiGnEIzTI3k/EIfvZFxFf4A3zp+lwe +AXwiraA==; Received: from 187-162-252-62.static.axtel.net ([187.162.252.62]:44004 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1isDEe-000egY-Bn; Thu, 16 Jan 2020 16:03:28 -0600 Date: Thu, 16 Jan 2020 16:03:27 -0600 From: "Gustavo A. R. Silva" To: Johan Hovold , Greg Kroah-Hartman Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] USB: serial: garmin_gps: Use flexible-array member Message-ID: <20200116220327.GA12537@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: 187.162.252.62 X-Source-L: No X-Exim-ID: 1isDEe-000egY-Bn X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 187-162-252-62.static.axtel.net (embeddedor) [187.162.252.62]:44004 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 3 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Old code in the kernel uses 1-byte and 0-byte arrays to indicate the presence of a "variable length array": struct something { int length; u8 data[1]; }; struct something *instance; instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL); instance->length = size; memcpy(instance->data, source, size); There is also 0-byte arrays. Both cases pose confusion for things like sizeof(), CONFIG_FORTIFY_SOURCE, etc.[1] Instead, the preferred mechanism to declare variable-length types such as the one above is a flexible array member[2] which need to be the last member of a structure and empty-sized: struct something { int stuff; u8 data[]; }; Also, 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 unadvertenly introduced[3] to the codebase from now on. [1] https://github.com/KSPP/linux/issues/21 [2] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva --- drivers/usb/serial/garmin_gps.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/serial/garmin_gps.c b/drivers/usb/serial/garmin_gps.c index 633550ec3025..ffd984142171 100644 --- a/drivers/usb/serial/garmin_gps.c +++ b/drivers/usb/serial/garmin_gps.c @@ -104,7 +104,7 @@ struct garmin_packet { int seq; /* the real size of the data array, always > 0 */ int size; - __u8 data[1]; + __u8 data[]; }; /* structure used to keep the current state of the driver */