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=-5.9 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=unavailable 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 5B9C3C43444 for ; Tue, 15 Jan 2019 08:20:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 33AC920859 for ; Tue, 15 Jan 2019 08:20:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728459AbfAOIUo (ORCPT ); Tue, 15 Jan 2019 03:20:44 -0500 Received: from smtp.eu.citrix.com ([185.25.65.24]:2019 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728085AbfAOIUn (ORCPT ); Tue, 15 Jan 2019 03:20:43 -0500 X-IronPort-AV: E=Sophos;i="5.56,481,1539648000"; d="scan'208";a="84595790" Date: Tue, 15 Jan 2019 09:20:36 +0100 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Dongli Zhang CC: , , , , , Subject: Re: [Xen-devel] [PATCH v6 2/2] xen/blkback: rework connect_ring() to avoid inconsistent xenstore 'ring-page-order' set by malicious blkfront Message-ID: <20190115082036.y7svi3xz3dkqd4w4@mac> References: <1547484104-20625-1-git-send-email-dongli.zhang@oracle.com> <1547484104-20625-2-git-send-email-dongli.zhang@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1547484104-20625-2-git-send-email-dongli.zhang@oracle.com> User-Agent: NeoMutt/20180716 X-ClientProxiedBy: AMSPEX02CAS02.citrite.net (10.69.22.113) To AMSPEX02CL02.citrite.net (10.69.22.126) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 15, 2019 at 12:41:44AM +0800, Dongli Zhang wrote: > The xenstore 'ring-page-order' is used globally for each blkback queue and > therefore should be read from xenstore only once. However, it is obtained > in read_per_ring_refs() which might be called multiple times during the > initialization of each blkback queue. > > If the blkfront is malicious and the 'ring-page-order' is set in different > value by blkfront every time before blkback reads it, this may end up at > the "WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));" in > xen_blkif_disconnect() when frontend is destroyed. > > This patch reworks connect_ring() to read xenstore 'ring-page-order' only > once. > > Signed-off-by: Dongli Zhang LGTM: Reviewed-by: Roger Pau Monné Thanks!