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=-6.3 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 12DC9C2D0A3 for ; Tue, 10 Nov 2020 02:07:09 +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 35C5020679 for ; Tue, 10 Nov 2020 02:07:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="iDfkNy15" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 35C5020679 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:56098 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kcJ3q-0003jh-S1 for qemu-devel@archiver.kernel.org; Mon, 09 Nov 2020 21:07:06 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:57598) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kcJ2a-0003Fl-Q4 for qemu-devel@nongnu.org; Mon, 09 Nov 2020 21:05:48 -0500 Received: from mail-oo1-xc44.google.com ([2607:f8b0:4864:20::c44]:33294) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1kcJ2Y-0004YK-Tg for qemu-devel@nongnu.org; Mon, 09 Nov 2020 21:05:48 -0500 Received: by mail-oo1-xc44.google.com with SMTP id f8so2220856oou.0 for ; Mon, 09 Nov 2020 18:05:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=IV1+dzDmKfWuDTE2Fa+9lksipHbrFo8+23DtZ9fotBI=; b=iDfkNy15r8saf1a5t0N88Bfvf58iIt5m2fOs1s9F6kShtWw2EV2jL+qxE2AbaaCm/C ZcymHUGTWBZyVyidwAzlZ85Re0ylTFM4IPkOVBp6yu//DWEYIIOg+ln9Q0Fa7SpabaIV sPHApY/fxCYYSM4vlKkfqfb99FTg2diUJvjQiq7Px1Mhoge4YZbeAmp16dQgmdTWJuPH mt8lsLhPj05DZ3Yn9WbJ4JyDRta+2I2unDOt62ajGYRVVTYgmFEG0m4qD/QjdVvDOlpN yj08KcZkHFFxw4tBCYl0myzpz8QMmX7RwlzdJLbb3gwlKxWUin4lvorxduEMu8q4V/NT 7JzA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=IV1+dzDmKfWuDTE2Fa+9lksipHbrFo8+23DtZ9fotBI=; b=K/Ct8akH10LSi5y0xHSWy2+X39BA/EIi9z+8ztaoUeYJXsEVMVEg1G0U9OPpCUX/LV h4AKwM52EZNz/qFGGmGx8BzWiNOfsGwUsPVA80gp8JKktOCz+dCllcJrRwE+kUxFWY7D fixxWicBB5s/6xyLRzRY39BL6zPf/mgpxYd4OVjUCvihtjSmTL0hF9q7qs5BD1MQMLDB OmJK2l4p3YwksiVoHmJ4vMBSLYTTxqDRhhPkpZ52lGZC9ZGIDtoRtFgBBYFwOyjhWylT mbnu3V/VSYJnW2dVDiHwj4JGcV3coQluN+m5NGxa2s6ERKxpjgUIkKP1XUZDXSpFAbtm SBvw== X-Gm-Message-State: AOAM533jTCV+2gyFzesRqkfCJtVfg4xQVJRORmKLpWRC4GFuJOMdiNEJ /cPuWjswzJoPF1geqUS7wW4dHTxPYUbGaqhyv0c= X-Google-Smtp-Source: ABdhPJy0GDAuQFyFcNSKFbZZmIDifDi7+zdu9IqvieeaYXh6HSnOvmy8wnoQVHUTUcFCIJOEgnc7Tm+3VO3pKDqq9rI= X-Received: by 2002:a4a:821a:: with SMTP id d26mr11923259oog.90.1604973944901; Mon, 09 Nov 2020 18:05:44 -0800 (PST) MIME-Version: 1.0 References: <20201109174355.1069147-1-stefanha@redhat.com> In-Reply-To: <20201109174355.1069147-1-stefanha@redhat.com> From: Raphael Norwitz Date: Mon, 9 Nov 2020 21:05:34 -0500 Message-ID: Subject: Re: [PATCH for-5.2] vhost-user: fix VHOST_USER_ADD/REM_MEM_REG truncation To: Stefan Hajnoczi Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2607:f8b0:4864:20::c44; envelope-from=raphael.s.norwitz@gmail.com; helo=mail-oo1-xc44.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. 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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, 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 , Cornelia Huck , "Michael S. Tsirkin" , QEMU , Raphael Norwitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Nov 9, 2020 at 12:59 PM 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. > > Fixes: f1aeb14b0809e313c74244d838645ed25e85ea63 ("Transmit vhost-user memory regions individually") > 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: Raphael Norwitz