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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 22C6EC606BD for ; Mon, 8 Jul 2019 15:25:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EDB27204EC for ; Mon, 8 Jul 2019 15:25:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1562599534; bh=0kw5P18G4j3qrgM0UcDgYuj3COmMTxB/GNf33UXOcts=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=n5FD+JrcaTefdZbfS4tazBxt8LfyR9x7CqGLN7vqPKR4aHu52+MdzfD3+ND343bzM kWA6FROQa9rC33bBqtlJls9efZ1czkZ3sA8Y27B+xfljU8qgAjpxpQbUTTv0Ix1sKT nC9ihoNDqZciYs27AX5HOEwjVbQLIu+J0O3tMYOQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388619AbfGHPZc (ORCPT ); Mon, 8 Jul 2019 11:25:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:52940 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388603AbfGHPZa (ORCPT ); Mon, 8 Jul 2019 11:25:30 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4E54F217D4; Mon, 8 Jul 2019 15:25:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1562599528; bh=0kw5P18G4j3qrgM0UcDgYuj3COmMTxB/GNf33UXOcts=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=klEDArTuEsefwaSzH4wjDJlFR7CXx3P2hjBnEDnefIg9r1YA5GuCVjwf3okwbNPTI SwAFOmyoP/dl+Z2mXL2HzJCuyTTnGLDhBEHd7FuP1KO6wrqTklU+oiWOp4h43Z4dp6 90T0wxVG/yAoW+DnSvjxG2uYZvAk0F/6AT0uqoCw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jason Wang , Stefan Hajnoczi , "Michael S. Tsirkin" , Balbir Singh Subject: [PATCH 4.14 45/56] vhost_net: fix possible infinite loop Date: Mon, 8 Jul 2019 17:13:37 +0200 Message-Id: <20190708150523.805847811@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190708150514.376317156@linuxfoundation.org> References: <20190708150514.376317156@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jason Wang commit e2412c07f8f3040593dfb88207865a3cd58680c0 upstream. When the rx buffer is too small for a packet, we will discard the vq descriptor and retry it for the next packet: while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk, &busyloop_intr))) { ... /* On overrun, truncate and discard */ if (unlikely(headcount > UIO_MAXIOV)) { iov_iter_init(&msg.msg_iter, READ, vq->iov, 1, 1); err = sock->ops->recvmsg(sock, &msg, 1, MSG_DONTWAIT | MSG_TRUNC); pr_debug("Discarded rx packet: len %zd\n", sock_len); continue; } ... } This makes it possible to trigger a infinite while..continue loop through the co-opreation of two VMs like: 1) Malicious VM1 allocate 1 byte rx buffer and try to slow down the vhost process as much as possible e.g using indirect descriptors or other. 2) Malicious VM2 generate packets to VM1 as fast as possible Fixing this by checking against weight at the end of RX and TX loop. This also eliminate other similar cases when: - userspace is consuming the packets in the meanwhile - theoretical TOCTOU attack if guest moving avail index back and forth to hit the continue after vhost find guest just add new buffers This addresses CVE-2019-3900. Fixes: d8316f3991d20 ("vhost: fix total length when packets are too short") Fixes: 3a4d5c94e9593 ("vhost_net: a kernel-level virtio server") Signed-off-by: Jason Wang Reviewed-by: Stefan Hajnoczi Signed-off-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman Signed-off-by: Balbir Singh --- drivers/vhost/net.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -482,7 +482,7 @@ static void handle_tx(struct vhost_net * hdr_size = nvq->vhost_hlen; zcopy = nvq->ubufs; - for (;;) { + do { /* Release DMAs done buffers first */ if (zcopy) vhost_zerocopy_signal_used(net, vq); @@ -578,10 +578,7 @@ static void handle_tx(struct vhost_net * else vhost_zerocopy_signal_used(net, vq); vhost_net_tx_packet(net); - if (unlikely(vhost_exceeds_weight(vq, ++sent_pkts, - total_len))) - break; - } + } while (likely(!vhost_exceeds_weight(vq, ++sent_pkts, total_len))); out: mutex_unlock(&vq->mutex); } @@ -779,7 +776,11 @@ static void handle_rx(struct vhost_net * vq->log : NULL; mergeable = vhost_has_feature(vq, VIRTIO_NET_F_MRG_RXBUF); - while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk))) { + do { + sock_len = vhost_net_rx_peek_head_len(net, sock->sk); + + if (!sock_len) + break; sock_len += sock_hlen; vhost_len = sock_len + vhost_hlen; headcount = get_rx_bufs(vq, vq->heads, vhost_len, @@ -860,9 +861,8 @@ static void handle_rx(struct vhost_net * vhost_log_write(vq, vq_log, log, vhost_len, vq->iov, in); total_len += vhost_len; - if (unlikely(vhost_exceeds_weight(vq, ++recv_pkts, total_len))) - goto out; - } + } while (likely(!vhost_exceeds_weight(vq, ++recv_pkts, total_len))); + vhost_net_enable_vq(net, vq); out: mutex_unlock(&vq->mutex); @@ -941,7 +941,7 @@ static int vhost_net_open(struct inode * vhost_net_buf_init(&n->vqs[i].rxq); } vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX, - VHOST_NET_WEIGHT, VHOST_NET_PKT_WEIGHT); + VHOST_NET_PKT_WEIGHT, VHOST_NET_WEIGHT); vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT, dev); vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN, dev);