From patchwork Thu May 7 18:39:09 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: 11534671 X-Patchwork-Delegate: johannes@sipsolutions.net 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 B6BCF14B4 for ; Thu, 7 May 2020 18:34:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9AE4220A8B for ; Thu, 7 May 2020 18:34:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588876488; bh=3SC5W/DS9xdMVSxaOxekzN7vcDdtHgz+8monE4FBn5k=; h=Date:From:To:Cc:Subject:List-ID:From; b=wPYtNQ8cx8TS39uoderJN2lDUSjhQZzoOFZT5p8qlffAq5bcBXPwYqzPWV/COzUpx atAluWUXkClHRMTxX3QcIoPsghWe9xU03ipM5TM6pxE03q2v6iaUKiitKCl+NsJFEi U/88jT/rjeHlMDYzuLcN71ivSpSx4GP+1sj1sOCg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728131AbgEGSeo (ORCPT ); Thu, 7 May 2020 14:34:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:35126 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726320AbgEGSen (ORCPT ); Thu, 7 May 2020 14:34:43 -0400 Received: from embeddedor (unknown [189.207.59.248]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A8435208E4; Thu, 7 May 2020 18:34:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588876483; bh=3SC5W/DS9xdMVSxaOxekzN7vcDdtHgz+8monE4FBn5k=; h=Date:From:To:Cc:Subject:From; b=TIux4fwoDb9uwopErmbP9RT5patBuiE/xSW5D8ARUAr0+g78M45DYZAgw0fu1W3JR Dr0Z5qOJPFF0ZD79Z7wlP2FekczbVV8B8RK+ZqhzpkeEEvYDJs1nlzlR35bq4VlGOR uVe0k8xwUp2JzNkJwheufKhcxMYn7nQXtjWD2EDA= Date: Thu, 7 May 2020 13:39:09 -0500 From: "Gustavo A. R. Silva" To: Johannes Berg Cc: linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] cfg80211: Replace zero-length array with flexible-array Message-ID: <20200507183909.GA12993@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@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] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. 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 --- include/linux/ieee80211.h | 6 +++--- include/net/cfg80211.h | 8 ++++---- net/wireless/core.h | 2 +- 3 files changed, 8 insertions(+), 8 deletions(-) diff --git a/include/linux/ieee80211.h b/include/linux/ieee80211.h index 16268ef1cbcc..e7d937871189 100644 --- a/include/linux/ieee80211.h +++ b/include/linux/ieee80211.h @@ -716,7 +716,7 @@ struct ieee80211_msrment_ie { u8 token; u8 mode; u8 type; - u8 request[0]; + u8 request[]; } __packed; /** @@ -1641,7 +1641,7 @@ struct ieee80211_he_operation { __le32 he_oper_params; __le16 he_mcs_nss_set; /* Optional 0,1,3,4,5,7 or 8 bytes: depends on @he_oper_params */ - u8 optional[0]; + u8 optional[]; } __packed; /** @@ -1653,7 +1653,7 @@ struct ieee80211_he_operation { struct ieee80211_he_spr { u8 he_sr_control; /* Optional 0 to 19 bytes: depends on @he_sr_control */ - u8 optional[0]; + u8 optional[]; } __packed; /** diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h index 70e48f66dac8..5eb776f0069d 100644 --- a/include/net/cfg80211.h +++ b/include/net/cfg80211.h @@ -2029,7 +2029,7 @@ struct cfg80211_scan_request { bool no_cck; /* keep last */ - struct ieee80211_channel *channels[0]; + struct ieee80211_channel *channels[]; }; static inline void get_random_mask_addr(u8 *buf, const u8 *addr, const u8 *mask) @@ -2175,7 +2175,7 @@ struct cfg80211_sched_scan_request { struct list_head list; /* keep last */ - struct ieee80211_channel *channels[0]; + struct ieee80211_channel *channels[]; }; /** @@ -2297,7 +2297,7 @@ struct cfg80211_bss { u8 bssid_index; u8 max_bssid_indicator; - u8 priv[0] __aligned(sizeof(void *)); + u8 priv[] __aligned(sizeof(void *)); }; /** @@ -4829,7 +4829,7 @@ struct wiphy { u8 max_data_retry_count; - char priv[0] __aligned(NETDEV_ALIGN); + char priv[] __aligned(NETDEV_ALIGN); }; static inline struct net *wiphy_net(struct wiphy *wiphy) diff --git a/net/wireless/core.h b/net/wireless/core.h index bb897a803ffe..151609b81096 100644 --- a/net/wireless/core.h +++ b/net/wireless/core.h @@ -290,7 +290,7 @@ struct cfg80211_cqm_config { u32 rssi_hyst; s32 last_rssi_event_value; int n_rssi_thresholds; - s32 rssi_thresholds[0]; + s32 rssi_thresholds[]; }; void cfg80211_destroy_ifaces(struct cfg80211_registered_device *rdev);