From patchwork Thu May 7 19:26:47 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: 11534803 X-Patchwork-Delegate: kvalo@adurom.com 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 EE11092A for ; Thu, 7 May 2020 19:22:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D620421835 for ; Thu, 7 May 2020 19:22:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879344; bh=cpk19YX7Aez2b3mVwHp6mHxj7I9/DZSqMJ91G22Vfuw=; h=Date:From:To:Cc:Subject:List-ID:From; b=2kvA5wxZ/LM0ELKUC9I/o9A17GgGDXYpFbWshhLP5FWkjc81K/LK/MHwKoYMaDirv FI5IQNjAOxakLOWJ1DZeij0cGGeZPYyWapR+iNYKsqtI79eW0iPW7i+JE6Q+W67uqd IAmy4ZPlEeSG7SCJ9ffLXxCho8e/gq6aXC0I//JU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728068AbgEGTWV (ORCPT ); Thu, 7 May 2020 15:22:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:43186 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726320AbgEGTWV (ORCPT ); Thu, 7 May 2020 15:22:21 -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 AC549208D6; Thu, 7 May 2020 19:22:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879341; bh=cpk19YX7Aez2b3mVwHp6mHxj7I9/DZSqMJ91G22Vfuw=; h=Date:From:To:Cc:Subject:From; b=AIUqiOSqMD+IbcKBnyrPQHUA15R8Vwt80WMpmUWte5KgIG+EoDtDpGP8hpwpG7p75 ph5gkgWPo0Jf4iTdULngqZrg2xMhTx9PQq9CnclBl/j3K7H8Hk9db96tH0GEXl4E4F FZZHnZDpyr0iFzrpuCxA62lxrSz5UwmVfY2nkoqs= Date: Thu, 7 May 2020 14:26:47 -0500 From: "Gustavo A. R. Silva" To: Jussi Kivilinna Cc: linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] rndis_wlan: Replace zero-length array with flexible-array Message-ID: <20200507192647.GA16710@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 --- drivers/net/wireless/rndis_wlan.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/net/wireless/rndis_wlan.c b/drivers/net/wireless/rndis_wlan.c index c8f8fe5497a8..52375f3e430a 100644 --- a/drivers/net/wireless/rndis_wlan.c +++ b/drivers/net/wireless/rndis_wlan.c @@ -201,7 +201,7 @@ struct ndis_80211_pmkid_candidate { struct ndis_80211_pmkid_cand_list { __le32 version; __le32 num_candidates; - struct ndis_80211_pmkid_candidate candidate_list[0]; + struct ndis_80211_pmkid_candidate candidate_list[]; } __packed; struct ndis_80211_status_indication { @@ -246,12 +246,12 @@ struct ndis_80211_bssid_ex { __le32 net_infra; u8 rates[NDIS_802_11_LENGTH_RATES_EX]; __le32 ie_length; - u8 ies[0]; + u8 ies[]; } __packed; struct ndis_80211_bssid_list_ex { __le32 num_items; - struct ndis_80211_bssid_ex bssid[0]; + struct ndis_80211_bssid_ex bssid[]; } __packed; struct ndis_80211_fixed_ies { @@ -333,7 +333,7 @@ struct ndis_80211_bssid_info { struct ndis_80211_pmkid { __le32 length; __le32 bssid_info_count; - struct ndis_80211_bssid_info bssid_info[0]; + struct ndis_80211_bssid_info bssid_info[]; } __packed; /*