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 isunable to handle extra_info segments being given
such a segment, causing it to crash.
This patch fixes the problem by gating whether the extra_info is sent
not only on the presence of a s/w hash, but also on whether the hash
algorithm has been configured.
Signed-off-by: Paul Durrant
Cc: Wei Liu
---
drivers/net/xen-netback/interface.c | 13 ++---
drivers/net/xen-netback/netback.c | 23 ++-
2 files changed, 16 insertions(+), 20 deletions(-)
diff --git a/drivers/net/xen-netback/interface.c
b/drivers/net/xen-netback/interface.c
index fb50c6d..1034139 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);
diff --git a/drivers/net/xen-netback/netback.c
b/drivers/net/xen-netback/netback.c
index 3d0c989..2cd4a8e 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -168,6 +168,10 @@ static bool xenvif_rx_ring_slots_available(struct
xenvif_queue *queue)
needed = DIV_ROUND_UP(skb->len, XEN_PAGE_SIZE);
if (skb_is_gso(skb))
needed++;
+ /* Assume the frontend is capable of handling the hash
+* extra_info at this point. This will only ever lead to an
+* accurate value or over-estimation.
+*/
if (skb->sw_hash)
needed++;
@@ -378,9 +382,8 @@ static void xenvif_gop_frag_copy(struct xenvif_queue
*queue, struct sk_buff *skb
.npo = npo,
.head = *head,
.gso_type = XEN_NETIF_GSO_TYPE_NONE,
- /* xenvif_set_skb_hash() will have either set a s/w
-* hash or cleared the hash depending on
-* whether the the frontend wants a hash for this skb.
+ /* xenvif_rx_action() will have cleared any hash if
+* the frontend is not capable of handling it.
*/
.hash_present = skb->sw_hash,
};
@@ -593,6 +596,14 @@ static void xenvif_rx_action(struct xenvif_queue *queue)
&& (skb = xenvif_rx_dequeue(queue)) != NULL) {
queue->last_rx_time = jiffies;
+ /* If there is no hash algorithm configured 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_CB(skb)->meta_slots_used = xenvif_gop_skb(skb, &npo,
queue);
__skb_queue_tail(&rxq, skb);
@@ -667,12 +678,6 @@ static void xenvif_rx_action(struct xenvif_queue *queue)
}
if (skb->sw_hash) {
- /* Since the skb got here via xenvif_select_queue()
-* we know that the hash has been re-calculated
-* according to a configuration set by the frontend
-* and therefore we know that it is legitimate to
-* pass it to the frontend.
-*/
if (resp->flags & XEN_NETRXF_extra_info)
extra->flags |= XEN_NETIF_EXTRA_FLAG_MORE;
else
--
2.1.4
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