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=-6.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 95FFAC388F7 for ; Mon, 9 Nov 2020 18:07:40 +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 C0BE320678 for ; Mon, 9 Nov 2020 18:07:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SQ7WbaHz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C0BE320678 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]:58498 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kcBZq-00083L-Jr for qemu-devel@archiver.kernel.org; Mon, 09 Nov 2020 13:07:38 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:45608) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kcBS2-0007xC-AD for qemu-devel@nongnu.org; Mon, 09 Nov 2020 12:59:34 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:28196) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kcBRz-0007IJ-Sf for qemu-devel@nongnu.org; Mon, 09 Nov 2020 12:59:33 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604944769; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Mc8ykPwYbsMSenXOrMSuvYfhJTig/4/IT0nAUvd6i2w=; b=SQ7WbaHzXpxmSvI0R7VLXiObRHG/+KmtTJYGTO9DJ10sdk9wHDFTlbj0+uEyW0vRlBm7B3 X2x3ux9CCiMjFKoy4D5t7r5iOLcrg1RO9Jz85grCnH5EMdL2McSwuIEhodepW8EZvxZFjS F8WvetF6YRVHcVY+hELtK7IyIDBTy2k= 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-154-Y_L6Jf13Pf-QB0W37N6Uow-1; Mon, 09 Nov 2020 12:59:27 -0500 X-MC-Unique: Y_L6Jf13Pf-QB0W37N6Uow-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 CC4BF1005513; Mon, 9 Nov 2020 17:59:26 +0000 (UTC) Received: from gondolin (ovpn-113-28.ams2.redhat.com [10.36.113.28]) by smtp.corp.redhat.com (Postfix) with ESMTP id 09FBA19C71; Mon, 9 Nov 2020 17:59:17 +0000 (UTC) Date: Mon, 9 Nov 2020 18:59:00 +0100 From: Cornelia Huck To: Stefan Hajnoczi Subject: Re: [PATCH for-5.2] vhost-user: fix VHOST_USER_ADD/REM_MEM_REG truncation Message-ID: <20201109185900.509417bf.cohuck@redhat.com> In-Reply-To: <20201109174355.1069147-1-stefanha@redhat.com> References: <20201109174355.1069147-1-stefanha@redhat.com> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=cohuck@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/09 01:25:23 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] 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_H5=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: , Cc: Christian Borntraeger , Raphael Norwitz , qemu-devel@nongnu.org, "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, 9 Nov 2020 17:43:55 +0000 Stefan Hajnoczi wrote: > QEMU currently truncates the mmap_offset field when sending > VHOST_USER_ADD_MEM_REG and VHOST_USER_REM_MEM_REG messages. The struct > layout looks like this: > > typedef struct VhostUserMemoryRegion { > uint64_t guest_phys_addr; > uint64_t memory_size; > uint64_t userspace_addr; > uint64_t mmap_offset; > } VhostUserMemoryRegion; > > typedef struct VhostUserMemRegMsg { > uint32_t padding; > /* WARNING: there is a 32-bit hole here! */ > VhostUserMemoryRegion region; > } VhostUserMemRegMsg; > > The payload size is calculated as follows when sending the message in > hw/virtio/vhost-user.c: > > msg->hdr.size = sizeof(msg->payload.mem_reg.padding) + > sizeof(VhostUserMemoryRegion); > > This calculation produces an incorrect result of only 36 bytes. > sizeof(VhostUserMemRegMsg) is actually 40 bytes. > > The consequence of this is that the final field, mmap_offset, is > truncated. This breaks x86_64 TCG guests on s390 hosts. Other guest/host > combinations may get lucky if either of the following holds: > 1. The guest memory layout does not need mmap_offset != 0. > 2. The host is little-endian and mmap_offset <= 0xffffffff so the > truncation has no effect. > > Fix this by extending the existing 32-bit padding field to 64-bit. Now > the padding reflects the actual compiler padding. This can be verified > using pahole(1). > > Also document the layout properly in the vhost-user specification. The > vhost-user spec did not document the exact layout. It would be > impossible to implement the spec without looking at the QEMU source > code. > > Existing vhost-user frontends and device backends continue to work after > this fix has been applied. The only change in the wire protocol is that > QEMU now sets hdr.size to 40 instead of 36. If a vhost-user > implementation has a hardcoded size check for 36 bytes, then it will > fail with new QEMUs. Both QEMU and DPDK/SPDK don't check the exact > payload size, so they continue to work. Seems we are lucky, then. > > Fixes: f1aeb14b0809e313c74244d838645ed25e85ea63 ("Transmit vhost-user memory regions individually") I think the canonical format is Fixes: f1aeb14b0809 ("Transmit vhost-user memory regions individually") Maybe cc:stable as well? > Cc: Raphael Norwitz > Cc: Cornelia Huck > Cc: Michael S. Tsirkin > Cc: Christian Borntraeger > Signed-off-by: Stefan Hajnoczi > --- > docs/interop/vhost-user.rst | 21 +++++++++++++++++++-- > contrib/libvhost-user/libvhost-user.h | 2 +- > hw/virtio/vhost-user.c | 5 ++--- > 3 files changed, 22 insertions(+), 6 deletions(-) Reviewed-by: Cornelia Huck