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virtio_net: fix use after free

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commit 0b725a2ca6
    net: Remove ndo_xmit_flush netdev operation, use signalling instead.

added code that looks at skb->xmit_more after the skb has
been put in TX VQ. Since some paths process the ring and free the skb
immediately, this can cause use after free.

Fix by storing xmit_more in a local variable.

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michael S. Tsirkin 2014-10-15 16:23:28 +03:00 committed by David S. Miller
parent 28b5f058cf
commit 4b7fd2e688
1 changed files with 3 additions and 1 deletions
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4
drivers/net/virtio_net.c
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@ -920,6 +920,8 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
int qnum = skb_get_queue_mapping(skb);
struct send_queue *sq = &vi->sq[qnum];
int err;
struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum);
bool kick = !skb->xmit_more;
/* Free up any pending old buffers before queueing new ones. */
free_old_xmit_skbs(sq);
@ -956,7 +958,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
}
}
if (__netif_subqueue_stopped(dev, qnum) || !skb->xmit_more)
if (kick || netif_xmit_stopped(txq))
virtqueue_kick(sq->vq);
return NETDEV_TX_OK;