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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 21454C3A59D for ; Thu, 10 Mar 2022 14:33:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244701AbiCJOdo (ORCPT ); Thu, 10 Mar 2022 09:33:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244123AbiCJO2a (ORCPT ); Thu, 10 Mar 2022 09:28:30 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6228BF539; Thu, 10 Mar 2022 06:23:17 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A00BB61B32; Thu, 10 Mar 2022 14:23:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AD4BDC340E8; Thu, 10 Mar 2022 14:23:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646922192; bh=B7AC+2jyNOILFU+cFx5Aid/yCzuBCeO7lVTC68n5Ens=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DuKX5Rjt3vW8hZfstjMgparX7R+ZRi3MsbHkOnRXCjel047ttjtBoqTgU9k8wt9LN yP0OfSfex+H2BkRPuoqJiXN6KJL72iYyccy8aYtaCitQZLzY+xQC3ivWC/ADJluMGX 4pGF7dbXLCZl2AbfjhEMOh6TnNEZ45V7fd2VcCLE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Demi Marie Obenour , Juergen Gross , Jan Beulich Subject: [PATCH 4.19 33/33] xen/netfront: react properly to failing gnttab_end_foreign_access_ref() Date: Thu, 10 Mar 2022 15:19:00 +0100 Message-Id: <20220310140808.718555574@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220310140807.749164737@linuxfoundation.org> References: <20220310140807.749164737@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Juergen Gross Commit 66e3531b33ee51dad17c463b4d9c9f52e341503d upstream. When calling gnttab_end_foreign_access_ref() the returned value must be tested and the reaction to that value should be appropriate. In case of failure in xennet_get_responses() the reaction should not be to crash the system, but to disable the network device. The calls in setup_netfront() can be replaced by calls of gnttab_end_foreign_access(). While at it avoid double free of ring pages and grant references via xennet_disconnect_backend() in this case. This is CVE-2022-23042 / part of XSA-396. Reported-by: Demi Marie Obenour Signed-off-by: Juergen Gross Reviewed-by: Jan Beulich Signed-off-by: Greg Kroah-Hartman --- drivers/net/xen-netfront.c | 48 +++++++++++++++++++++++++++++---------------- 1 file changed, 31 insertions(+), 17 deletions(-) --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -862,7 +862,6 @@ static int xennet_get_responses(struct n int max = XEN_NETIF_NR_SLOTS_MIN + (rx->status <= RX_COPY_THRESHOLD); int slots = 1; int err = 0; - unsigned long ret; if (rx->flags & XEN_NETRXF_extra_info) { err = xennet_get_extras(queue, extras, rp); @@ -893,8 +892,13 @@ static int xennet_get_responses(struct n goto next; } - ret = gnttab_end_foreign_access_ref(ref, 0); - BUG_ON(!ret); + if (!gnttab_end_foreign_access_ref(ref, 0)) { + dev_alert(dev, + "Grant still in use by backend domain\n"); + queue->info->broken = true; + dev_alert(dev, "Disabled for further use\n"); + return -EINVAL; + } gnttab_release_grant_reference(&queue->gref_rx_head, ref); @@ -1098,6 +1102,10 @@ static int xennet_poll(struct napi_struc err = xennet_get_responses(queue, &rinfo, rp, &tmpq); if (unlikely(err)) { + if (queue->info->broken) { + spin_unlock(&queue->rx_lock); + return 0; + } err: while ((skb = __skb_dequeue(&tmpq))) __skb_queue_tail(&errq, skb); @@ -1676,7 +1684,7 @@ static int setup_netfront(struct xenbus_ struct netfront_queue *queue, unsigned int feature_split_evtchn) { struct xen_netif_tx_sring *txs; - struct xen_netif_rx_sring *rxs; + struct xen_netif_rx_sring *rxs = NULL; grant_ref_t gref; int err; @@ -1696,21 +1704,21 @@ static int setup_netfront(struct xenbus_ err = xenbus_grant_ring(dev, txs, 1, &gref); if (err < 0) - goto grant_tx_ring_fail; + goto fail; queue->tx_ring_ref = gref; rxs = (struct xen_netif_rx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH); if (!rxs) { err = -ENOMEM; xenbus_dev_fatal(dev, err, "allocating rx ring page"); - goto alloc_rx_ring_fail; + goto fail; } SHARED_RING_INIT(rxs); FRONT_RING_INIT(&queue->rx, rxs, XEN_PAGE_SIZE); err = xenbus_grant_ring(dev, rxs, 1, &gref); if (err < 0) - goto grant_rx_ring_fail; + goto fail; queue->rx_ring_ref = gref; if (feature_split_evtchn) @@ -1723,22 +1731,28 @@ static int setup_netfront(struct xenbus_ err = setup_netfront_single(queue); if (err) - goto alloc_evtchn_fail; + goto fail; return 0; /* If we fail to setup netfront, it is safe to just revoke access to * granted pages because backend is not accessing it at this point. */ -alloc_evtchn_fail: - gnttab_end_foreign_access_ref(queue->rx_ring_ref, 0); -grant_rx_ring_fail: - free_page((unsigned long)rxs); -alloc_rx_ring_fail: - gnttab_end_foreign_access_ref(queue->tx_ring_ref, 0); -grant_tx_ring_fail: - free_page((unsigned long)txs); -fail: + fail: + if (queue->rx_ring_ref != GRANT_INVALID_REF) { + gnttab_end_foreign_access(queue->rx_ring_ref, 0, + (unsigned long)rxs); + queue->rx_ring_ref = GRANT_INVALID_REF; + } else { + free_page((unsigned long)rxs); + } + if (queue->tx_ring_ref != GRANT_INVALID_REF) { + gnttab_end_foreign_access(queue->tx_ring_ref, 0, + (unsigned long)txs); + queue->tx_ring_ref = GRANT_INVALID_REF; + } else { + free_page((unsigned long)txs); + } return err; }