From patchwork Thu May 7 18:59:07 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: 11534725 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 8909A15AB for ; Thu, 7 May 2020 18:54:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7245C216FD for ; Thu, 7 May 2020 18:54:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877686; bh=uxpX8W7aK8UmLVlFFNK05ClZR+zoFt4I4ufIGsyleuA=; h=Date:From:To:Cc:Subject:List-ID:From; b=aYRgrhHOG8ABSmayiKRmdL8+9UKLuJelqkqh6hBkd5ueEtikIFHkZZtnHMssw8RrG HhDRYrzUfyG5n523fWA+qxWHhuv3tJuPzIUbVQivT4xu7xIwlccoiS1+Sxo3Y6hNZ/ /uoJGMnoery/Oi8DTRr1923JcXjXj286jnI8rbPw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727964AbgEGSym (ORCPT ); Thu, 7 May 2020 14:54:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:56810 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726558AbgEGSym (ORCPT ); Thu, 7 May 2020 14:54:42 -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 0AB2420575; Thu, 7 May 2020 18:54:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877681; bh=uxpX8W7aK8UmLVlFFNK05ClZR+zoFt4I4ufIGsyleuA=; h=Date:From:To:Cc:Subject:From; b=Vc7Ojvfaumf23QiCyhoZU7rgfQM7qZWnMc9F7sDKwBz5Fa8dG1rMcR7efJArM37jo /glLdysDlzCdQ4oezSPYRv66bu9fsD1vtNntmkl4VB9E8u9Hsw1AD3ZMiaG9SfMDOq PLyr2FzlG6QXrMwbPPjjAosGJzmdikG0983dF4tk= Date: Thu, 7 May 2020 13:59:07 -0500 From: "Gustavo A. R. Silva" To: Johannes Berg Cc: linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] mac80211: Replace zero-length array with flexible-array Message-ID: <20200507185907.GA15102@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/net/mac80211.h | 10 +++++----- net/mac80211/ieee80211_i.h | 2 +- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/include/net/mac80211.h b/include/net/mac80211.h index b6b4de0e4b5e..75ff87b860a4 100644 --- a/include/net/mac80211.h +++ b/include/net/mac80211.h @@ -230,7 +230,7 @@ struct ieee80211_chanctx_conf { bool radar_enabled; - u8 drv_priv[0] __aligned(sizeof(void *)); + u8 drv_priv[] __aligned(sizeof(void *)); }; /** @@ -1652,7 +1652,7 @@ struct ieee80211_vif { bool txqs_stopped[IEEE80211_NUM_ACS]; /* must be last */ - u8 drv_priv[0] __aligned(sizeof(void *)); + u8 drv_priv[] __aligned(sizeof(void *)); }; static inline bool ieee80211_vif_is_mesh(struct ieee80211_vif *vif) @@ -1780,7 +1780,7 @@ struct ieee80211_key_conf { s8 keyidx; u16 flags; u8 keylen; - u8 key[0]; + u8 key[]; }; #define IEEE80211_MAX_PN_LEN 16 @@ -2035,7 +2035,7 @@ struct ieee80211_sta { struct ieee80211_txq *txq[IEEE80211_NUM_TIDS + 1]; /* must be last */ - u8 drv_priv[0] __aligned(sizeof(void *)); + u8 drv_priv[] __aligned(sizeof(void *)); }; /** @@ -2081,7 +2081,7 @@ struct ieee80211_txq { u8 ac; /* must be last */ - u8 drv_priv[0] __aligned(sizeof(void *)); + u8 drv_priv[] __aligned(sizeof(void *)); }; /** diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h index f8ed4f621f7f..ea483861b743 100644 --- a/net/mac80211/ieee80211_i.h +++ b/net/mac80211/ieee80211_i.h @@ -267,7 +267,7 @@ struct probe_resp { struct rcu_head rcu_head; int len; u16 csa_counter_offsets[IEEE80211_MAX_CSA_COUNTERS_NUM]; - u8 data[0]; + u8 data[]; }; struct ps_data {