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virtio: fix virtio_net xmit of freed skb bug

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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: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
This commit is contained in:
Rusty Russell 2008-05-26 17:42:42 +10:00 committed by Jeff Garzik
parent d399cf8c04
commit 7eb2e25112
1 changed files with 9 additions and 5 deletions
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14
drivers/net/virtio_net.c
View file

@ -287,21 +287,25 @@ 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 */
__skb_queue_head(&vi->send, skb);
if (xmit_skb(vi, skb) != 0) {
vi->last_xmit_skb = skb;
goto stop_queue;
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);