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Commit 7eb2e251 authored by Rusty Russell's avatar Rusty Russell Committed by Jeff Garzik
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virtio: fix virtio_net xmit of freed skb bug 



If we fail to transmit a packet, we assume the queue is full and put
the skb into last_xmit_skb.  However, if more space frees up before we
xmit it, we loop, and the result can be transmitting the same skb twice.

Fix is simple: set skb to NULL if we've used it in some way, and check
before sending.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarJeff Garzik <jgarzik@redhat.com>
parent d399cf8c

drivers/net/virtio_net.c

+9 −5
Original line number Diff line number Diff line
@@ -287,22 +287,26 @@ static int start_xmit(struct sk_buff *skb, struct net_device *dev) 
	free_old_xmit_skbs(vi);



	/* If we has a buffer left over from last time, send it now. */

	if (vi->last_xmit_skb) {

	if (unlikely(vi->last_xmit_skb)) {

		if (xmit_skb(vi, vi->last_xmit_skb) != 0) {

			/* Drop this skb: we only queue one. */

			vi->dev->stats.tx_dropped++;

			kfree_skb(skb);

			skb = NULL;

			goto stop_queue;

		}

		vi->last_xmit_skb = NULL;

	}



	/* Put new one in send queue and do transmit */

	if (likely(skb)) {

		__skb_queue_head(&vi->send, skb);

		if (xmit_skb(vi, skb) != 0) {

			vi->last_xmit_skb = skb;

			skb = NULL;

			goto stop_queue;

		}

	}

done:

	vi->svq->vq_ops->kick(vi->svq);

	return NETDEV_TX_OK;