Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753734AbcJ1Jee (ORCPT ); Fri, 28 Oct 2016 05:34:34 -0400 Received: from mail.us.es ([193.147.175.20]:53822 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751913AbcJ1Jec (ORCPT ); Fri, 28 Oct 2016 05:34:32 -0400 Date: Fri, 28 Oct 2016 11:34:22 +0200 From: Pablo Neira Ayuso To: Simon Horman , Julian Anastasov Cc: Arnd Bergmann , Wensong Zhang , Patrick McHardy , Jozsef Kadlecsik , "David S. Miller" , Quentin Armitage , netdev@vger.kernel.org, lvs-devel@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] netfilter: ip_vs_sync: fix bogus maybe-uninitialized warning Message-ID: <20161028093422.GA29559@salvia> References: <20161024153454.2766113-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2708 Lines: 50 On Mon, Oct 24, 2016 at 10:47:54PM +0300, Julian Anastasov wrote: > > Hello, > > On Mon, 24 Oct 2016, Arnd Bergmann wrote: > > > Building the ip_vs_sync code with CONFIG_OPTIMIZE_INLINING on x86 > > confuses the compiler to the point where it produces a rather > > dubious warning message: > > > > net/netfilter/ipvs/ip_vs_sync.c:1073:33: error: ‘opt.init_seq’ may be used uninitialized in this function [-Werror=maybe-uninitialized] > > struct ip_vs_sync_conn_options opt; > > ^~~ > > net/netfilter/ipvs/ip_vs_sync.c:1073:33: error: ‘opt.delta’ may be used uninitialized in this function [-Werror=maybe-uninitialized] > > net/netfilter/ipvs/ip_vs_sync.c:1073:33: error: ‘opt.previous_delta’ may be used uninitialized in this function [-Werror=maybe-uninitialized] > > net/netfilter/ipvs/ip_vs_sync.c:1073:33: error: ‘*((void *)&opt+12).init_seq’ may be used uninitialized in this function [-Werror=maybe-uninitialized] > > net/netfilter/ipvs/ip_vs_sync.c:1073:33: error: ‘*((void *)&opt+12).delta’ may be used uninitialized in this function [-Werror=maybe-uninitialized] > > net/netfilter/ipvs/ip_vs_sync.c:1073:33: error: ‘*((void *)&opt+12).previous_delta’ may be used uninitialized in this function [-Werror=maybe-uninitialized] > > > > The problem appears to be a combination of a number of factors, including > > the __builtin_bswap32 compiler builtin being slightly odd, having a large > > amount of code inlined into a single function, and the way that some > > functions only get partially inlined here. > > > > I've spent way too much time trying to work out a way to improve the > > code, but the best I've come up with is to add an explicit memset > > right before the ip_vs_seq structure is first initialized here. When > > the compiler works correctly, this has absolutely no effect, but in the > > case that produces the warning, the warning disappears. > > > > In the process of analysing this warning, I also noticed that > > we use memcpy to copy the larger ip_vs_sync_conn_options structure > > over two members of the ip_vs_conn structure. This works because > > the layout is identical, but seems error-prone, so I'm changing > > this in the process to directly copy the two members. This change > > seemed to have no effect on the object code or the warning, but > > it deals with the same data, so I kept the two changes together. > > > > Signed-off-by: Arnd Bergmann > > OK, > > Acked-by: Julian Anastasov > > I guess, Simon will take the patch for ipvs-next. @Simon: If you have no more pending updates, I can save you one pull request for this small fix by placing this. Thanks!