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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7C66DC433EF for ; Mon, 27 Jun 2022 15:35:01 +0000 (UTC) Received: from localhost ([::1]:48584 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1o5qlQ-0005V7-B1 for qemu-devel@archiver.kernel.org; Mon, 27 Jun 2022 11:35:00 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40178) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o5qkB-0004d6-C8 for qemu-devel@nongnu.org; Mon, 27 Jun 2022 11:33:43 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:45305) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o5qk8-0003Qz-D5 for qemu-devel@nongnu.org; Mon, 27 Jun 2022 11:33:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1656344019; 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: in-reply-to:in-reply-to:references:references; bh=NZ+++UP5A+FlFcT5xn6GTZU0qNkT3o9w3tD5+HOMncE=; b=ZXOCCkbj6zriBuibDjE6jM5lysvoaqWXavPkCpEHN2fwIdeJn5faH8ZV22fLpUJWrAf0pK TOKZzCI+SKy/f5aEULJ6l6GTw7e0w1s7/7Ivc1FjMeFlwXag2eDsa0Ro/U5N8U4StLFjQB fUtCODbghnMi1pUXzBAlVRczoBaUnow= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-595-k5JMT3CbMHe_eXuHHVAGLA-1; Mon, 27 Jun 2022 11:33:33 -0400 X-MC-Unique: k5JMT3CbMHe_eXuHHVAGLA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 958062806AC0; Mon, 27 Jun 2022 15:33:31 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.195.112]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 636032166B26; Mon, 27 Jun 2022 15:33:31 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 464EA21E690D; Mon, 27 Jun 2022 17:33:30 +0200 (CEST) From: Markus Armbruster To: Peter Maydell Cc: Paolo Bonzini , QEMU Developers Subject: Re: use of uninitialized variable involving visit_type_uint32() and friends References: Date: Mon, 27 Jun 2022 17:33:30 +0200 In-Reply-To: (Peter Maydell's message of "Mon, 27 Jun 2022 14:33:52 +0100") Message-ID: <87o7ye15px.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Peter Maydell writes: > On Fri, 1 Apr 2022 at 09:08, Paolo Bonzini wrote: >> >> >> >> On Thu, Mar 31, 2022 at 7:35 PM Peter Maydell wrote: >>> >>> Coverity warns about use of uninitialized data in what seems >>> to be a common pattern of use of visit_type_uint32() and similar >>> functions. Here's an example from target/arm/cpu64.c: >>> >>> static void cpu_max_set_sve_max_vq(Object *obj, Visitor *v, const char *name, >>> void *opaque, Error **errp) >>> { >>> ARMCPU *cpu = ARM_CPU(obj); >>> uint32_t max_vq; >>> if (!visit_type_uint32(v, name, &max_vq, errp)) { >>> return; >>> } >>> [code that does something with max_vq here] >>> } >>> >>> This doesn't initialize max_vq, on the apparent assumption >>> that visit_type_uint32() will do so. But that function [...] >>> reads the value of *obj (the uninitialized max_vq). >> >> >> The visit_type_* functions are written to work for both getters and setters. >> For the leaves, that means potentially reading uninitialized data. It is >> harmless but very ugly, and with respect to static analysis it was all but >> a time bomb, all the time. >> >> The best (but most intrusive) solution would be to add a parameter to all >> visit_type_* functions with the expected "direction" of the visit, which >> could be checked against v->type. > > So do we have a plan for what we want to do with this issue? > > In the meantime, any objections to my just marking all the Coverity > issues which are pointing out that visit_* functions use uninitialized > data as 'false positive' ? There are a ton of them, and they clog up > the issue UI and make it hard to see other actually interesting reports. I think to object, I would have to propose an alternative with a reasonable chance of success within a reasonable time frame. I can't, so I won't. Paolo proposed improvements, and I think they're worth exploring, but such musings fall well short of my condition for "may object".