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=-13.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_GIT 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 DFF9FC43387 for ; Mon, 7 Jan 2019 05:33:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F73C20657 for ; Mon, 7 Jan 2019 05:33:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="aBO3Jtcd" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725775AbfAGFdK (ORCPT ); Mon, 7 Jan 2019 00:33:10 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:34076 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725300AbfAGFdJ (ORCPT ); Mon, 7 Jan 2019 00:33:09 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id x075TTFu044828; Mon, 7 Jan 2019 05:33:02 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references; s=corp-2018-07-02; bh=HFmgqRUGYAr+ce8tSaVIhfeOWNuvZrD3gSKUgjEFETc=; b=aBO3JtcdQ7LRy84M+oGTSnid9LcupdKRbKNAIUO6PNf1+pssbkbzpKJjShcHmA6wx0KT E6GuhUMhw+xidbb94tJny0wjlGczfWtE0jSLnBcyH6XsRSqh4d4F5a+JMC+yiK+ZnrPI 0k4psOFhtIP3HSQBxshu4ilEX2amZ33+VT4HSmt1r2gn4FBV5mJpC+X55h7K6AsVT+lh qzRUjHTbt1IEOcBjU4xjQAQwnefZJj8L6HK7501wovO3uzdnnbyvgD4vqdhYv1k6fQcK 9oBCQhYRnqDmX3qipMKsGJQAX5VjfqbWB0oP8HKmigMGmxWdLgVjvdqH/aBx1a+zVSYN Sw== Received: from userv0021.oracle.com (userv0021.oracle.com [156.151.31.71]) by userp2120.oracle.com with ESMTP id 2ptn7qkn9t-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 07 Jan 2019 05:33:02 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x075X2dM024200 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 7 Jan 2019 05:33:02 GMT Received: from abhmp0013.oracle.com (abhmp0013.oracle.com [141.146.116.19]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x075X1No007169; Mon, 7 Jan 2019 05:33:01 GMT Received: from linux.cn.oracle.com (/10.182.69.241) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Sun, 06 Jan 2019 21:33:01 -0800 From: Dongli Zhang To: xen-devel@lists.xenproject.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: konrad.wilk@oracle.com, roger.pau@citrix.com, axboe@kernel.dk, Paul.Durrant@citrix.com Subject: [PATCH v4 2/2] xen/blkback: rework connect_ring() to avoid inconsistent xenstore 'ring-page-order' set by malicious blkfront Date: Mon, 7 Jan 2019 13:35:59 +0800 Message-Id: <1546839359-5478-2-git-send-email-dongli.zhang@oracle.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1546839359-5478-1-git-send-email-dongli.zhang@oracle.com> References: <1546839359-5478-1-git-send-email-dongli.zhang@oracle.com> X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9128 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901070048 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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 --- Changed since v1: * change the order of xenstore read in read_per_ring_refs * use xenbus_read_unsigned() in connect_ring() Changed since v2: * simplify the condition check as "(err != 1 && nr_grefs > 1)" * avoid setting err as -EINVAL to remove extra one line of code Changed since v3: * exit at the beginning if !nr_grefs * change the if statements to avoid test (err != 1) twice * initialize a 'blkif' stack variable (refer to PATCH 1/2) drivers/block/xen-blkback/xenbus.c | 76 +++++++++++++++++++++----------------- 1 file changed, 43 insertions(+), 33 deletions(-) diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index a4aadac..a2acbc9 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -926,7 +926,7 @@ static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir) int err, i, j; struct xen_blkif *blkif = ring->blkif; struct xenbus_device *dev = blkif->be->dev; - unsigned int ring_page_order, nr_grefs, evtchn; + unsigned int nr_grefs, evtchn; err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u", &evtchn); @@ -936,43 +936,38 @@ static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir) return err; } - err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-page-order", "%u", - &ring_page_order); - if (err != 1) { - err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u", &ring_ref[0]); + nr_grefs = blkif->nr_ring_pages; + + if (unlikely(!nr_grefs)) + return -EINVAL; + + for (i = 0; i < nr_grefs; i++) { + char ring_ref_name[RINGREF_NAME_LEN]; + + snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i); + err = xenbus_scanf(XBT_NIL, dir, ring_ref_name, + "%u", &ring_ref[i]); + if (err != 1) { - err = -EINVAL; - xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir); - return err; - } - nr_grefs = 1; - } else { - unsigned int i; - - if (ring_page_order > xen_blkif_max_ring_order) { - err = -EINVAL; - xenbus_dev_fatal(dev, err, "%s/request %d ring page order exceed max:%d", - dir, ring_page_order, - xen_blkif_max_ring_order); - return err; + if (nr_grefs == 1) + break; + + xenbus_dev_fatal(dev, err, "reading %s/%s", + dir, ring_ref_name); + return -EINVAL; } + } - nr_grefs = 1 << ring_page_order; - for (i = 0; i < nr_grefs; i++) { - char ring_ref_name[RINGREF_NAME_LEN]; - - snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i); - err = xenbus_scanf(XBT_NIL, dir, ring_ref_name, - "%u", &ring_ref[i]); - if (err != 1) { - err = -EINVAL; - xenbus_dev_fatal(dev, err, "reading %s/%s", - dir, ring_ref_name); - return err; - } + if (err != 1) { + WARN_ON(nr_grefs != 1); + + err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u", + &ring_ref[0]); + if (err != 1) { + xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir); + return -EINVAL; } } - blkif->nr_ring_pages = nr_grefs; for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) { req = kzalloc(sizeof(*req), GFP_KERNEL); @@ -1031,6 +1026,7 @@ static int connect_ring(struct backend_info *be) size_t xspathsize; const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */ unsigned int requested_num_queues = 0; + unsigned int ring_page_order; pr_debug("%s %s\n", __func__, dev->otherend); @@ -1076,6 +1072,20 @@ static int connect_ring(struct backend_info *be) blkif->nr_rings, blkif->blk_protocol, protocol, pers_grants ? "persistent grants" : ""); + ring_page_order = xenbus_read_unsigned(dev->otherend, + "ring-page-order", 0); + + if (ring_page_order > xen_blkif_max_ring_order) { + err = -EINVAL; + xenbus_dev_fatal(dev, err, + "requested ring page order %d exceed max:%d", + ring_page_order, + xen_blkif_max_ring_order); + return err; + } + + blkif->nr_ring_pages = 1 << ring_page_order; + if (blkif->nr_rings == 1) return read_per_ring_refs(&blkif->rings[0], dev->otherend); else { -- 2.7.4