From patchwork Mon Feb 17 21:43:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. 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R. Silva" To: Marek Lindner , Simon Wunderlich , Antonio Quartulli , Sven Eckelmann , "David S. Miller" , Jakub Kicinski Subject: [PATCH][next] batman-adv: Replace zero-length array with flexible-array member Message-ID: <20200217214300.GA14129@embeddedor> MIME-Version: 1.0 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 - lists.open-mesh.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 200.68.140.26 X-Source-L: No X-Exim-ID: 1j3o7m-001GXx-EB X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.68.140.26]:16142 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 8 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=open-mesh.org; s=20121; t=1581975622; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: dkim-signature; bh=Up3NXkZ9MtOum0S7bVKL3huOyiNJmhlgLtMxveQ6vXs=; b=jNcg7L1AG+HxBMr+IZcbwX1WSN5RpOoUG0LgiZ4ft9qZUOLR6fxiF9Xo2GU0ktjwOXIvmP d0D1V+VVbXyK4Wb6tFNUdZXfmVTRL5/kqX3rYR+7P/JAid29KfIrG4JRXSgNMooobgrVri mbQ+yAKvZkqF5Cqb3TZnACSMOdLKCEw= ARC-Seal: i=1; s=20121; d=open-mesh.org; t=1581975622; a=rsa-sha256; cv=none; b=LFXSdiqo3udFQRJ5D1TYqa9vbg5IgLtta31em8ckSJMj/rG8W3EsiMT3qGd7wYL3mxLyiE OVNf1fXEfYk7hiky+8MeBWw2TF8JZnhd/gGXqvC4xUmmryku4QRbfYlNdAQxjv1+iD8VKe GmWi8igatSEGqeKOEIeaxzWZ6k87KWM= ARC-Authentication-Results: i=1; diktynna.open-mesh.org; dkim=pass header.d=embeddedor.com header.s=default header.b=fQRsoHfi; spf=pass (diktynna.open-mesh.org: domain of gustavo@embeddedor.com designates 192.185.47.79 as permitted sender) smtp.mailfrom=gustavo@embeddedor.com X-Mailman-Approved-At: Mon, 17 Feb 2020 22:42:50 +0100 X-BeenThere: b.a.t.m.a.n@lists.open-mesh.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: The list for a Better Approach To Mobile Ad-hoc Networking List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: The list for a Better Approach To Mobile Ad-hoc Networking Cc: netdev@vger.kernel.org, b.a.t.m.a.n@lists.open-mesh.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Errors-To: b.a.t.m.a.n-bounces@lists.open-mesh.org Sender: "B.A.T.M.A.N" 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] 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 --- net/batman-adv/distributed-arp-table.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c index 3d21dd83f8cc..b85da4b7a77b 100644 --- a/net/batman-adv/distributed-arp-table.c +++ b/net/batman-adv/distributed-arp-table.c @@ -88,7 +88,7 @@ struct batadv_dhcp_packet { __u8 sname[64]; __u8 file[128]; __be32 magic; - __u8 options[0]; + __u8 options[]; }; #define BATADV_DHCP_YIADDR_LEN sizeof(((struct batadv_dhcp_packet *)0)->yiaddr)