virtio_net: fix use after free
commit 0b725a2ca61bedc33a2a63d0451d528b268cf975
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>
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 3d0ce44..13d0a8b 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -920,6 +920,8 @@
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 @@
}
}
- if (__netif_subqueue_stopped(dev, qnum) || !skb->xmit_more)
+ if (kick || netif_xmit_stopped(txq))
virtqueue_kick(sq->vq);
return NETDEV_TX_OK;
