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xen-netback: make sure that hashes are not send to unaware frontends

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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 <paul.durrant@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paul Durrant 2016-10-07 09:32:31 +01:00 committed by David S. Miller
parent 21d9629a7a
commit 912e27e85e
1 changed files with 9 additions and 11 deletions
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20
drivers/net/xen-netback/interface.c
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@ -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);