From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A803C282DA for ; Wed, 17 Apr 2019 09:01:14 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5747420693 for ; Wed, 17 Apr 2019 09:01:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="tz+PFq1m"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="QspXLNji" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5747420693 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=THRPIYxzHn4dVhTnvNNXunAwuP82RuXCxbCAReymMfI=; b=tz+PFq1mGxGPzu xPSyC30cq8uwDRj+AGLWJ55ZSD779df0T0CMCr2a94iYVrUqy+4kA80xmyHAPr+cqpsqIjmIHgmC3 1+SDU1Gw9Gvd4F/MdEJkIkWfQLmZidUM3M2mhXY/mnvPEhKfMLzDzs2WEw5kxWzs6ZIEoDOHgRiX1 J+jByFIWUzFxkqE+Za1W4/BdaqnjVS/h8Xf7Yh1w2WRpYeSE8yT8m65fM+bh3pLWpvUZZDLpyAhbt gZWlYv6CRqdtWWdcbpR1puAcF3lTvGMzw33N4t54nGkIX5QDXaL6BnE/qbwSo60VV+bAK2EG3N2kz wOyAX4MMCWByKEAJB+aw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hGgRJ-000392-PU; Wed, 17 Apr 2019 09:01:09 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hGgRH-00038J-5C for linux-arm-kernel@lists.infradead.org; Wed, 17 Apr 2019 09:01:08 +0000 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 31DA621773; Wed, 17 Apr 2019 09:01:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1555491664; bh=BEasVom47PMugj24F1KQvqhVPi/jf4xgcIShQ0cct9Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QspXLNjinfzU9rdPnzoDUmzYu+ZBLtgi1/C5H/RtSr6uCWUIOmCVE46zf6esKcOru 0zfa7igR1qJ/ZdLWMoYZdW7eGE/eNhKGcZjbQoMrhmgurXyOgkd2qwKkx4nnsHYF5M DWd41Wmk5zsEyxsctviG4vKhIAVMd6bposfoTndY= Date: Wed, 17 Apr 2019 11:01:02 +0200 From: Greg Kroah-Hartman To: Nathan Chancellor Subject: Re: [PATCH] arm64: futex: Restore oldval initialization to work around buggy compilers Message-ID: <20190417090102.GA11773@kroah.com> References: <20190417072121.4450-1-natechancellor@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190417072121.4450-1-natechancellor@gmail.com> User-Agent: Mutt/1.11.4 (2019-03-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190417_020107_215982_BC6DF474 X-CRM114-Status: GOOD ( 10.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Catalin Marinas , stable@vger.kernel.org, Will Deacon , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Apr 17, 2019 at 12:21:21AM -0700, Nathan Chancellor wrote: > Commit 045afc24124d ("arm64: futex: Fix FUTEX_WAKE_OP atomic ops with > non-zero result value") removed oldval's zero initialization in > arch_futex_atomic_op_inuser because it is not necessary. Unfortunately, > Android's arm64 GCC 4.9.4 [1] does not agree: > > ../kernel/futex.c: In function 'do_futex': > ../kernel/futex.c:1658:17: warning: 'oldval' may be used uninitialized > in this function [-Wmaybe-uninitialized] > return oldval == cmparg; > ^ > In file included from ../kernel/futex.c:73:0: > ../arch/arm64/include/asm/futex.h:53:6: note: 'oldval' was declared here > int oldval, ret, tmp; > ^ > > GCC fails to follow that when ret is non-zero, futex_atomic_op_inuser > returns right away, avoiding the uninitialized use that it claims. > Restoring the zero initialization works around this issue. > > [1]: https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/ > > Cc: stable@vger.kernel.org > Fixes: 045afc24124d ("arm64: futex: Fix FUTEX_WAKE_OP atomic ops with non-zero result value") > Signed-off-by: Nathan Chancellor Reviewed-by: Greg Kroah-Hartman _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel