virtio-net: correct error handling of virtqueue_kick()

[ Upstream commit 681daee2443291419c57cccb0671f5f94a839005 ]

Current error handling of virtqueue_kick() was wrong in two places:
- The skb were freed immediately when virtqueue_kick() fail during
  xmit. This may lead double free since the skb was not detached from
  the virtqueue.
- try_fill_recv() returns false when virtqueue_kick() fail. This will
  lead unnecessary rescheduling of refill work.

Actually, it's safe to just ignore the kick failure in those two
places. So this patch fixes this by partially revert commit
67975901183799af8e93ec60e322f9e2a1940b9b.

Fixes 67975901183799af8e93ec60e322f9e2a1940b9b
(virtio_net: verify if virtqueue_kick() succeeded).

Cc: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 8eb6b9d75cef9b33d685a58cded717e98716fa59..19d96c889aac8a516ea2e9cb45bec0e7a2b93d57 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -633,8 +633,7 @@ static bool try_fill_recv(struct receive_queue *rq, gfp_t gfp)
        } while (rq->vq->num_free);
        if (unlikely(rq->num > rq->max))
                rq->max = rq->num;
-       if (unlikely(!virtqueue_kick(rq->vq)))
-               return false;
+       virtqueue_kick(rq->vq);
        return !oom;
 }
 
@@ -840,7 +839,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
        err = xmit_skb(sq, skb);
 
        /* This should not happen! */
-       if (unlikely(err) || unlikely(!virtqueue_kick(sq->vq))) {
+       if (unlikely(err)) {
                dev->stats.tx_fifo_errors++;
                if (net_ratelimit())
                        dev_warn(&dev->dev,
@@ -849,6 +848,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
                kfree_skb(skb);
                return NETDEV_TX_OK;
        }
+       virtqueue_kick(sq->vq);
 
        /* Don't wait up for transmitted skbs to be freed. */
        skb_orphan(skb);