From patchwork Mon Feb 17 20:05:00 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: 11387579 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 1853317E8 for ; Mon, 17 Feb 2020 20:52:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EC910207FD for ; Mon, 17 Feb 2020 20:52:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=embeddedor.com header.i=@embeddedor.com header.b="gHGlMLhH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728142AbgBQUwN (ORCPT ); Mon, 17 Feb 2020 15:52:13 -0500 Received: from gateway34.websitewelcome.com ([192.185.46.126]:17358 "EHLO gateway22.websitewelcome.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1727300AbgBQUwN (ORCPT ); Mon, 17 Feb 2020 15:52:13 -0500 X-Greylist: delayed 1501 seconds by postgrey-1.27 at vger.kernel.org; Mon, 17 Feb 2020 15:52:12 EST Received: from cm17.websitewelcome.com (cm17.websitewelcome.com [100.42.49.20]) by gateway22.websitewelcome.com (Postfix) with ESMTP id B8B2B7415 for ; Mon, 17 Feb 2020 14:02:20 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 3mayju4LhAGTX3mayj5E9v; Mon, 17 Feb 2020 14:02:20 -0600 X-Authority-Reason: nr=8 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=embeddedor.com; s=default; h=Content-Type:MIME-Version:Message-ID:Subject: Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=Ecty6MerGyd7wX45GYrcBWDuJacrGQZzyDnGictr5cU=; b=gHGlMLhH/8NwV+4WcyPOTRykq/ Habr4VE/lVhtlFHsYItOo+hL9NTTW56IU2lJ8eGl1qfEf86QE6sJhsb1LUT+k7QS5FBgH/tJAPzIo Px0tsesC+EQj8bcXjlR+XbKKH9KmMUEv+6W5gSg/ydaU+W7A+FKL4R+4E6v3iHUZsYOSiAkXCJ/54 Ule61XOWKpBeAkgzX1D0TpNShvbRdycWsUB0j1fyw/Oaei+VE9ecNQSUgIjTbCspp9+mXKU3kZhXF 5NJoeeilulftg49oTqYf9IqAeOCUVeRc0Zmwivo4/6O+aaMo/E5JdzL5g42onE87HssaHFRBC0CWM B1TpV0jg==; Received: from [200.68.140.26] (port=23900 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j3max-000Q8w-00; Mon, 17 Feb 2020 14:02:19 -0600 Date: Mon, 17 Feb 2020 14:05:00 -0600 From: "Gustavo A. R. Silva" To: Trond Myklebust , Anna Schumaker , "J. Bruce Fields" , Chuck Lever , "David S. Miller" , Jakub Kicinski Cc: linux-nfs@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] svcrdma: Replace zero-length array with flexible-array member Message-ID: <20200217200500.GA7628@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 - vger.kernel.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: 1j3max-000Q8w-00 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.68.140.26]:23900 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 7 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@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] 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/sunrpc/xprtrdma/svc_rdma_rw.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c index 48fe3b16b0d9..003610ce00bc 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_rw.c +++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c @@ -41,7 +41,7 @@ struct svc_rdma_rw_ctxt { struct rdma_rw_ctx rw_ctx; int rw_nents; struct sg_table rw_sg_table; - struct scatterlist rw_first_sgl[0]; + struct scatterlist rw_first_sgl[]; }; static inline struct svc_rdma_rw_ctxt *