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=-13.1 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,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 90FBBC32771 for ; Mon, 20 Jan 2020 23:45:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4886D22522 for ; Mon, 20 Jan 2020 23:45:34 +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="piP3faKZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728512AbgATXpc (ORCPT ); Mon, 20 Jan 2020 18:45:32 -0500 Received: from gateway24.websitewelcome.com ([192.185.50.45]:13692 "EHLO gateway24.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727045AbgATXpc (ORCPT ); Mon, 20 Jan 2020 18:45:32 -0500 Received: from cm17.websitewelcome.com (cm17.websitewelcome.com [100.42.49.20]) by gateway24.websitewelcome.com (Postfix) with ESMTP id 6C51739372 for ; Mon, 20 Jan 2020 17:45:30 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id tgjaiZWCr9jb7tgjaigW5v; Mon, 20 Jan 2020 17:45:30 -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=07Tf64pQAmiDup6FxV7EE+r4VySFfyDuXyrZ0/gMUto=; b=piP3faKZqz2doeRGcQSKBn+2CQ 5qTWjr0PJRQjA67oeh4/fcgmhwJNeC+kG+RixCUxJeqBA70H0VnvPxVHN/KYAkxRHRyZHlnfugMf6 4UF7GT9V7LbGkWPRPT6mSa41DTiFA+q1W1wQYp8fRm1vDQj+cjNwK7t9sqrgto7uVJ4gpMqTetFOB 9DhzZf7Do+pypt919RDNCfVIBeIEKX72k8P34n+NwKBioNY7Q/t/HfNWb8vCJlyxM/GN93a40/TgJ 5RI3EUEwjEZSoTw9WJCkcvLlLh9jJTBjhZMsIJuTtv+AMt3Qfelclutz64AGncyNayMjW9f66ch+I D7CNZYxA==; Received: from 187-162-252-62.static.axtel.net ([187.162.252.62]:44948 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1itgjZ-003jVH-5v; Mon, 20 Jan 2020 17:45:29 -0600 Date: Mon, 20 Jan 2020 17:45:28 -0600 From: "Gustavo A. R. Silva" To: Greg Kroah-Hartman , Jiri Slaby Cc: linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] tty: n_hdlc: Use flexible-array member Message-ID: <20200120234528.GA26790@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: 1itgjZ-003jVH-5v X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 187-162-252-62.static.axtel.net (embeddedor) [187.162.252.62]:44948 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 3 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/tty/n_hdlc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c index 98361acd3053..b5499ca8757e 100644 --- a/drivers/tty/n_hdlc.c +++ b/drivers/tty/n_hdlc.c @@ -115,7 +115,7 @@ struct n_hdlc_buf { struct list_head list_item; int count; - char buf[1]; + char buf[]; }; #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe) -- 2.23.0