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=-15.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 1C633C2BA83 for ; Fri, 14 Feb 2020 16:49:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DB1F92082F for ; Fri, 14 Feb 2020 16:49:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581698954; bh=OpgiaQBuOcxxfIy7NsvXii2pSTZUaY4k6dIJUggnapM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Ui3rfOcuDN8cg18/QDK2pKEWtTIB7qhoYxEivdRexTJBjj1/v8DWe4wTDzEiJtTzY UiOESsOUY/fJeRKAKCXoMggO28DBJE3KhpEuRGxpZllAAOFxNdpIFCKUWkh55HoBlz EvUNzO7mhDBi2LW8loX4chRpSTGEavVpe7TkrmV4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393036AbgBNQtN (ORCPT ); Fri, 14 Feb 2020 11:49:13 -0500 Received: from mail.kernel.org ([198.145.29.99]:54458 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392860AbgBNQUf (ORCPT ); Fri, 14 Feb 2020 11:20:35 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4B32524739; Fri, 14 Feb 2020 16:20:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581697234; bh=OpgiaQBuOcxxfIy7NsvXii2pSTZUaY4k6dIJUggnapM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TX/sb4viUSbQ0BAo/xZR0wMQbL1ne/tQQNrEsN+B0yXG+oH0s3lEsQx/LbpJ8+F+S KRYb0V9tl3TYnUtiqWzEXlie1IRM/ngQuz+mPOpCiR5nIXeJxrbc7ScGmvphWttevO Tihw7SnjPuw4AR1jczoPdY521wgC5WGivKFeFwA4= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Gustavo A. R. Silva" , Greg Kroah-Hartman , Sasha Levin Subject: [PATCH AUTOSEL 4.14 156/186] char: hpet: Use flexible-array member Date: Fri, 14 Feb 2020 11:16:45 -0500 Message-Id: <20200214161715.18113-156-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200214161715.18113-1-sashal@kernel.org> References: <20200214161715.18113-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Gustavo A. R. Silva" [ Upstream commit 987f028b8637cfa7658aa456ae73f8f21a7a7f6f ] 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 Link: https://lore.kernel.org/r/20200120235326.GA29231@embeddedor.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- 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 05ca269ddd05b..40ba552551324 100644 --- a/drivers/char/hpet.c +++ b/drivers/char/hpet.c @@ -113,7 +113,7 @@ 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; -- 2.20.1