From mboxrd@z Thu Jan 1 00:00:00 1970 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=-13.0 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=ham 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 EB1ACC32771 for ; Tue, 21 Jan 2020 00:14:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BA27E24650 for ; Tue, 21 Jan 2020 00:14:03 +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="cdURJ4B2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728816AbgAUAOC (ORCPT ); Mon, 20 Jan 2020 19:14:02 -0500 Received: from gateway32.websitewelcome.com ([192.185.145.113]:26512 "EHLO gateway32.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727009AbgAUAOA (ORCPT ); Mon, 20 Jan 2020 19:14:00 -0500 X-Greylist: delayed 1231 seconds by postgrey-1.27 at vger.kernel.org; Mon, 20 Jan 2020 19:14:00 EST Received: from cm17.websitewelcome.com (cm17.websitewelcome.com [100.42.49.20]) by gateway32.websitewelcome.com (Postfix) with ESMTP id 7277C141ADEF for ; Mon, 20 Jan 2020 17:53:28 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id tgrIiZbYB9jb7tgrIigbNb; Mon, 20 Jan 2020 17:53:28 -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=xxAzhTqbOqe1BRFg2/D6CHH4pUnAKV9fRR68rERoFdo=; b=cdURJ4B2sUTFx/0XYpxi8YfVRe ZluDtH1/J/eWhM4ZhDHvMayLsFgRrnBpF37tElMKjlhiQrMOBiVi2RJuy5LJmCgE6XlVZ2WuM3/8j 6cv2Ru7V6SCeZoJqvGgXnR1ZiGoR2Jq47TiCkZnHys2Hdu9rI0B0nte+GQuCxcHal1ec9O4A+jw70 smaPrztSNaecMnmYzyHWMqDzBSv3Ua7ztO45zm5FmaWaOhvME8xLNAJZhRxk/v8d9XS+SSSWn9iRX n8jMvpVJjCaQ7yy/td1V3yeCDupgun+USnAgjDw0nS+YvtU+8NFMaa03OXcN0cF7Crg3AAlhH+dov VnKCp1AQ==; Received: from 187-162-252-62.static.axtel.net ([187.162.252.62]:44974 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1itgrH-003oDh-72; Mon, 20 Jan 2020 17:53:27 -0600 Date: Mon, 20 Jan 2020 17:53:26 -0600 From: "Gustavo A. R. Silva" To: Clemens Ladisch , Arnd Bergmann , Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] char: hpet: Use flexible-array member Message-ID: <20200120235326.GA29231@embeddedor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii 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: 1itgrH-003oDh-72 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 187-162-252-62.static.axtel.net (embeddedor) [187.162.252.62]:44974 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 7 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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/char/hpet.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c index 9ac6671bb514..aed2c45f7968 100644 --- a/drivers/char/hpet.c +++ b/drivers/char/hpet.c @@ -110,7 +110,7 @@ struct hpets { unsigned long hp_delta; unsigned int hp_ntimer; unsigned int hp_which; - struct hpet_dev hp_dev[1]; + struct hpet_dev hp_dev[]; }; static struct hpets *hpets; -- 2.23.0