From patchwork Mon Dec 20 14:35:27 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 526384 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 E4520C433FE for ; Mon, 20 Dec 2021 15:01:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237510AbhLTPBv (ORCPT ); Mon, 20 Dec 2021 10:01:51 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:49682 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240040AbhLTO7v (ORCPT ); Mon, 20 Dec 2021 09:59:51 -0500 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 B7ABD6119E; Mon, 20 Dec 2021 14:59:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1704C36AE8; Mon, 20 Dec 2021 14:59:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1640012390; bh=nih9dZrU8O63ScahyWDZ8/H1Eobq4ZvyR31ISJE4lLM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0ZgnlxqHJVNCsvE325Gb6dB23vsUzii6m8LUtcTAgxnk6y9LXOhe6Pk4jSTz4sbGX BKoxUv0KjIYZ1U2tSW1I+b1cSfrMeNjjgQ0e7rCLVa1PxkWdHTETxHSMalLw79tx5C rpLODZguCl1ANXyA9VyYZn41wVI1+3erNnroQyVs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Juergen Gross , Jan Beulich Subject: [PATCH 5.15 177/177] xen/netback: dont queue unlimited number of packages Date: Mon, 20 Dec 2021 15:35:27 +0100 Message-Id: <20211220143046.021909815@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211220143040.058287525@linuxfoundation.org> References: <20211220143040.058287525@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Juergen Gross commit be81992f9086b230623ae3ebbc85ecee4d00a3d3 upstream. In case a guest isn't consuming incoming network traffic as fast as it is coming in, xen-netback is buffering network packages in unlimited numbers today. This can result in host OOM situations. Commit f48da8b14d04ca8 ("xen-netback: fix unlimited guest Rx internal queue and carrier flapping") meant to introduce a mechanism to limit the amount of buffered data by stopping the Tx queue when reaching the data limit, but this doesn't work for cases like UDP. When hitting the limit don't queue further SKBs, but drop them instead. In order to be able to tell Rx packages have been dropped increment the rx_dropped statistics counter in this case. It should be noted that the old solution to continue queueing SKBs had the additional problem of an overflow of the 32-bit rx_queue_len value would result in intermittent Tx queue enabling. This is part of XSA-392 Fixes: f48da8b14d04ca8 ("xen-netback: fix unlimited guest Rx internal queue and carrier flapping") Signed-off-by: Juergen Gross Reviewed-by: Jan Beulich Signed-off-by: Greg Kroah-Hartman --- drivers/net/xen-netback/rx.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) --- a/drivers/net/xen-netback/rx.c +++ b/drivers/net/xen-netback/rx.c @@ -88,16 +88,19 @@ void xenvif_rx_queue_tail(struct xenvif_ spin_lock_irqsave(&queue->rx_queue.lock, flags); - if (skb_queue_empty(&queue->rx_queue)) - xenvif_update_needed_slots(queue, skb); - - __skb_queue_tail(&queue->rx_queue, skb); - - queue->rx_queue_len += skb->len; - if (queue->rx_queue_len > queue->rx_queue_max) { + if (queue->rx_queue_len >= queue->rx_queue_max) { struct net_device *dev = queue->vif->dev; netif_tx_stop_queue(netdev_get_tx_queue(dev, queue->id)); + kfree_skb(skb); + queue->vif->dev->stats.rx_dropped++; + } else { + if (skb_queue_empty(&queue->rx_queue)) + xenvif_update_needed_slots(queue, skb); + + __skb_queue_tail(&queue->rx_queue, skb); + + queue->rx_queue_len += skb->len; } spin_unlock_irqrestore(&queue->rx_queue.lock, flags); @@ -147,6 +150,7 @@ static void xenvif_rx_queue_drop_expired break; xenvif_rx_dequeue(queue); kfree_skb(skb); + queue->vif->dev->stats.rx_dropped++; } }