From: Juergen Gross jgross@suse.com
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 jgross@suse.com Reviewed-by: Jan Beulich jbeulich@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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++; } }