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 39E45CED624 for ; Tue, 18 Nov 2025 11:53:23 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vLKGO-0004GI-F4; Tue, 18 Nov 2025 06:52:48 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vLKGM-0004FW-Ax for qemu-devel@nongnu.org; Tue, 18 Nov 2025 06:52:46 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vLKGI-0000RZ-Qp for qemu-devel@nongnu.org; Tue, 18 Nov 2025 06:52:45 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763466761; 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=s5fv3dUZKjQiYXMfdkaNYBm2pMHDgivpCnRn7HgCay0=; b=F6+qvM96c7x8H90Nc8vOzm8Ss3sEIYJJJvfrzn9TcCnq6exu6b7u5AXO2YLxPKqAx+CL4P iZOUlXyTCE1vT030qkfMQSiPoS8RTkXzZdbdALUeP7vhe0zh6RLGuHvOfkdTAADewHko3Z vemgMNp2PUiapTHfxl20k9FsZRLA34I= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-669-6qXPkewGOjiV-AZMO2HF8g-1; Tue, 18 Nov 2025 06:52:37 -0500 X-MC-Unique: 6qXPkewGOjiV-AZMO2HF8g-1 X-Mimecast-MFC-AGG-ID: 6qXPkewGOjiV-AZMO2HF8g_1763466756 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D5FD9180034D; Tue, 18 Nov 2025 11:52:35 +0000 (UTC) Received: from localhost (dhcp-192-224.str.redhat.com [10.33.192.224]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B43273003754; Tue, 18 Nov 2025 11:52:34 +0000 (UTC) From: Cornelia Huck To: Thomas Huth , qemu-s390x@nongnu.org, Christian Borntraeger , Halil Pasic , Eric Farman , Matthew Rosato Cc: qemu-devel@nongnu.org, David Hildenbrand , =?utf-8?Q?C=C3=A9dric?= Le Goater Subject: Re: [PATCH v2] hw/s390x: Fix a possible crash with passed-through virtio devices In-Reply-To: <20251118093945.35062-1-thuth@redhat.com> Organization: "Red Hat GmbH, Sitz: Werner-von-Siemens-Ring 12, D-85630 Grasbrunn, Handelsregister: Amtsgericht =?utf-8?Q?M=C3=BCnchen=2C?= HRB 153243, =?utf-8?Q?Gesch=C3=A4ftsf=C3=BChrer=3A?= Ryan Barnhart, Charles Cachera, Avril Crosse O'Flaherty" References: <20251118093945.35062-1-thuth@redhat.com> User-Agent: Notmuch/0.38.3 (https://notmuchmail.org) Date: Tue, 18 Nov 2025 12:52:32 +0100 Message-ID: <87ms4jr20v.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-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: 2.1.29 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Nov 18 2025, Thomas Huth wrote: > From: Thomas Huth > > Consider the following nested setup: An L1 host uses some virtio device > (e.g. virtio-keyboard) for the L2 guest, and this L2 guest passes this > device through to the L3 guest. Since the L3 guest sees a virtio device, > it might send virtio notifications to the QEMU in L2 for that device. > But since the QEMU in L2 defined this device as vfio-ccw, the function > handle_virtio_ccw_notify() cannot handle this and crashes: It calls > virtio_ccw_get_vdev() that casts sch->driver_data into a VirtioCcwDevice, > but since "sch" belongs to a vfio-ccw device, that driver_data rather > points to a CcwDevice instead. So as soon as QEMU tries to use some > VirtioCcwDevice specific data from that device, we've lost. > > We must not take virtio notifications for such devices. Thus fix the > issue by adding a check to the handle_virtio_ccw_notify() handler to > refuse all devices that are not our own virtio devices. > > Signed-off-by: Thomas Huth > --- > v2: Now with the required #include statement > > hw/s390x/s390-hypercall.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/hw/s390x/s390-hypercall.c b/hw/s390x/s390-hypercall.c > index ac1b08b2cd5..38f1c6132e0 100644 > --- a/hw/s390x/s390-hypercall.c > +++ b/hw/s390x/s390-hypercall.c > @@ -10,6 +10,7 @@ > */ > > #include "qemu/osdep.h" > +#include "qemu/error-report.h" > #include "cpu.h" > #include "hw/s390x/s390-virtio-ccw.h" > #include "hw/s390x/s390-hypercall.h" > @@ -42,6 +43,18 @@ static int handle_virtio_ccw_notify(uint64_t subch_id, uint64_t data) > if (!sch || !css_subch_visible(sch)) { > return -EINVAL; > } > + if (sch->id.cu_type != VIRTIO_CCW_CU_TYPE) { > + /* > + * This might happen in nested setups: If the L1 host defined the > + * L2 guest with a virtio device (e.g. virtio-keyboard), and the > + * L2 guest passes this device through to the L3 guest, the L3 guest > + * might send virtio notifications to the QEMU in L2 for that device. > + * But since the QEMU in L2 defined this device as vfio-ccw, it's not > + * a VirtIODevice that we can handle here! > + */ > + warn_report_once("Got virtio notification for unsupported device!"); Maybe also print which device ended up here? > + return -EINVAL; > + } > > vdev = virtio_ccw_get_vdev(sch); > if (vq_idx >= VIRTIO_QUEUE_MAX || !virtio_queue_get_num(vdev, vq_idx)) {