From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Liu Subject: Re: [PATCH v2 net] xen-netback: make sure that hashes are not send to unaware frontends Date: Fri, 7 Oct 2016 10:07:58 +0100 Message-ID: <20161007090758.GB3687@citrix.com> References: <1475829151-3707-1-git-send-email-paul.durrant@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: , , Wei Liu To: Paul Durrant Return-path: Received: from smtp.citrix.com ([66.165.176.89]:36995 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755537AbcJGJIL (ORCPT ); Fri, 7 Oct 2016 05:08:11 -0400 Content-Disposition: inline In-Reply-To: <1475829151-3707-1-git-send-email-paul.durrant@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Oct 07, 2016 at 09:32:31AM +0100, Paul Durrant wrote: > In the case when a frontend only negotiates a single queue with xen- > netback it is possible for a skbuff with a s/w hash to result in a > hash extra_info segment being sent to the frontend even when no hash > algorithm has been configured. (The ndo_select_queue() entry point makes > sure the hash is not set if no algorithm is configured, but this entry > point is not called when there is only a single queue). This can result > in a frontend that is unable to handle extra_info segments being given > such a segment, causing it to crash. > > This patch fixes the problem by clearing the hash in ndo_start_xmit() > instead, which is clearly guaranteed to be called irrespective of the > number of queues. > > Signed-off-by: Paul Durrant > Cc: Wei Liu Acked-by: Wei Liu > --- > > v2: > - Simplified and re-based onto re-factored net branch > --- > drivers/net/xen-netback/interface.c | 20 +++++++++----------- > 1 file changed, 9 insertions(+), 11 deletions(-) > > diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c > index 4af532a..74dc2bf 100644 > --- a/drivers/net/xen-netback/interface.c > +++ b/drivers/net/xen-netback/interface.c > @@ -149,17 +149,8 @@ static u16 xenvif_select_queue(struct net_device *dev, struct sk_buff *skb, > struct xenvif *vif = netdev_priv(dev); > unsigned int size = vif->hash.size; > > - if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE) { > - u16 index = fallback(dev, skb) % dev->real_num_tx_queues; > - > - /* Make sure there is no hash information in the socket > - * buffer otherwise it would be incorrectly forwarded > - * to the frontend. > - */ > - skb_clear_hash(skb); > - > - return index; > - } > + if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE) > + return fallback(dev, skb) % dev->real_num_tx_queues; > > xenvif_set_skb_hash(vif, skb); > > @@ -208,6 +199,13 @@ static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev) > cb = XENVIF_RX_CB(skb); > cb->expires = jiffies + vif->drain_timeout; > > + /* If there is no hash algorithm configured then make sure there > + * is no hash information in the socket buffer otherwise it > + * would be incorrectly forwarded to the frontend. > + */ > + if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE) > + skb_clear_hash(skb); > + > xenvif_rx_queue_tail(queue, skb); > xenvif_kick_thread(queue); > > -- > 2.1.4 >