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=-10.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 9D213C433E6 for ; Tue, 26 Jan 2021 10:37:53 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 1601B23108 for ; Tue, 26 Jan 2021 10:37:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1601B23108 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:59896 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l4LjM-0001dz-4H for qemu-devel@archiver.kernel.org; Tue, 26 Jan 2021 05:37:52 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:54224) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l4LiC-0000cE-QP for qemu-devel@nongnu.org; Tue, 26 Jan 2021 05:36:40 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:54161) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l4LiA-0002R8-73 for qemu-devel@nongnu.org; Tue, 26 Jan 2021 05:36:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611657397; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zKyiTPtPLHtPQSG2e57kNl7rl5h28FRdybsWaStyL7c=; b=UTwliTgVLe1jMX39x7WieZwMo1Bs0sckuwJD9z6IYBObWQqcZHJWk8p9gLgP6Q7ettkvXR nOjOQZuvrlfPhaikZKAyGPBH4nmRDCk2XOrkvnufOeJIX7cnJruS6ssVKGvYkuP4kBwASM g67eLVA+aDBRtsyjQ9yQXKq2k7NHVEU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-483-9IZwiJqUPcevFYdYJCXDig-1; Tue, 26 Jan 2021 05:36:35 -0500 X-MC-Unique: 9IZwiJqUPcevFYdYJCXDig-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9573A8030A8; Tue, 26 Jan 2021 10:36:34 +0000 (UTC) Received: from redhat.com (ovpn-115-101.ams2.redhat.com [10.36.115.101]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 78A7F19934; Tue, 26 Jan 2021 10:36:22 +0000 (UTC) Date: Tue, 26 Jan 2021 10:36:19 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Stefan Hajnoczi Subject: Re: [PATCH v2] virtiofsd: prevent opening of special files (CVE-2020-35517) Message-ID: <20210126103619.GD3640294@redhat.com> References: <20210126103502.260758-1-stefanha@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210126103502.260758-1-stefanha@redhat.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.255, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: mszeredi@redhat.com, slp@redhat.com, qemu-devel@nongnu.org, "Dr. David Alan Gilbert" , virtio-fs@redhat.com, Alex Xu , P J P , Laszlo Ersek , vgoyal@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Jan 26, 2021 at 10:35:02AM +0000, Stefan Hajnoczi wrote: > A well-behaved FUSE client does not attempt to open special files with > FUSE_OPEN because they are handled on the client side (e.g. device nodes > are handled by client-side device drivers). > > The check to prevent virtiofsd from opening special files is missing in > a few cases, most notably FUSE_OPEN. A malicious client can cause > virtiofsd to open a device node, potentially allowing the guest to > escape. This can be exploited by a modified guest device driver. It is > not exploitable from guest userspace since the guest kernel will handle > special files inside the guest instead of sending FUSE requests. > > This patch adds the missing checks to virtiofsd. This is a short-term > solution because it does not prevent a compromised virtiofsd process > from opening device nodes on the host. > > Reported-by: Alex Xu > Fixes: CVE-2020-35517 > Reviewed-by: Dr. David Alan Gilbert > Reviewed-by: Vivek Goyal > Signed-off-by: Stefan Hajnoczi Reviewed-by: Daniel P. Berrangé Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|