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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS autolearn=no 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 E91D3C433E0 for ; Tue, 16 Feb 2021 16:07:20 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 A78E664DA5 for ; Tue, 16 Feb 2021 16:07:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A78E664DA5 Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=xenproject.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.85903.160757 (Exim 4.92) (envelope-from ) id 1lC2sU-0000Cx-FK; Tue, 16 Feb 2021 16:07:06 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 85903.160757; Tue, 16 Feb 2021 16:07:06 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lC2sU-0000Cq-Ba; Tue, 16 Feb 2021 16:07:06 +0000 Received: by outflank-mailman (input) for mailman id 85903; Tue, 16 Feb 2021 16:07:05 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lC2sS-0000CQ-VD for xen-devel@lists.xenproject.org; Tue, 16 Feb 2021 16:07:04 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lC2sS-00047J-Qz for xen-devel@lists.xenproject.org; Tue, 16 Feb 2021 16:07:04 +0000 Received: from iwj (helo=mariner.uk.xensource.com) by xenbits.xenproject.org with local-bsmtp (Exim 4.92) (envelope-from ) id 1lC2sS-0003qC-Pi for xen-devel@lists.xenproject.org; Tue, 16 Feb 2021 16:07:04 +0000 Received: from iwj by mariner.uk.xensource.com with local (Exim 4.89) (envelope-from ) id 1lC2sP-0000j7-Kn; Tue, 16 Feb 2021 16:07:01 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xenproject.org; s=20200302mail; h=References:In-Reply-To:Subject:Cc:To:Date :Message-ID:Content-Transfer-Encoding:Content-Type:MIME-Version:From; bh=KPxoidAHBajHVmadRtmD47OFaWAuEME/xon5R2DQX0U=; b=Bl7xw4wGHCPuYX7E7xLSZsQ+8i b5I+II1XYD4QzBojXS/i7aHWta9zLrFQraCGyydibWwtUxRDe/FUkZWeAz9KkbhYhDBsmTc2G3yVh uQn+Td4mU/k3PtkLdUEvgk5ioj+pFF2nTG5LtwEFlBPiqUPpwaeK3QrY79Ley1TKpuC4=; From: Ian Jackson MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <24619.60837.362896.565993@mariner.uk.xensource.com> Date: Tue, 16 Feb 2021 16:07:01 +0000 To: Andrew Cooper Cc: Xen-devel , Ian Jackson , Wei Liu , Anthony PERARD Subject: Re: [PATCH 04/10] tools/libxl: Fix uninitialised variable in libxl__domain_get_device_model_uid() In-Reply-To: <20210212153953.4582-5-andrew.cooper3@citrix.com> References: <20210212153953.4582-1-andrew.cooper3@citrix.com> <20210212153953.4582-5-andrew.cooper3@citrix.com> X-Mailer: VM 8.2.0b under 24.5.1 (i686-pc-linux-gnu) Andrew Cooper writes ("[PATCH 04/10] tools/libxl: Fix uninitialised variable in libxl__domain_get_device_model_uid()"): > The logic is sufficiently complicated I can't figure out if the complain is > legitimate or not. There is exactly one path wanting kill_by_uid set to true, > so default it to false and drop the existing workaround for this problem at > other optimisation levels. The place where it's used is here: if (!rc && user) { state->dm_runas = user; if (kill_by_uid) state->dm_kill_uid = GCSPRINTF("%ld",... This is gated by !rc. So for this to be used uninitialised, we'd have to get here with rc==0 but uninitialised kill_by_uid. The label `out` is preceded by a nonzero assignment to rc. All the `goto out` are preceded by either (i) nonzero assignment to rc, or (ii) assignment to kill_by_uid and setting rc=0. So the compiler is wrong. If only we had sum types. In the absence of sum types I suggest the following restructuring: Change all the `rc = ERROR...; goto out;` to `goto err` and make `goto out` be the success path only. Ian.