vhost_net: examine pointer types during un-producing

After commit fc72d1d ("tuntap: XDP transmission"), we can
actually queueing XDP pointers in the pointer ring, so we should
examine the pointer type before freeing the pointer.

Fixes: fc72d1d ("tuntap: XDP transmission")
Reported-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tun.c

@@ -655,7 +655,7 @@ static struct tun_struct *tun_enable_queue(struct tun_file *tfile)
 	return tun;
 }
 
-static void tun_ptr_free(void *ptr)
+void tun_ptr_free(void *ptr)
 {
 	if (!ptr)
 		return;
@@ -667,6 +667,7 @@ static void tun_ptr_free(void *ptr)
 		__skb_array_destroy_skb(ptr);
 	}
 }
+EXPORT_SYMBOL_GPL(tun_ptr_free);
 
 static void tun_queue_purge(struct tun_file *tfile)
 {

drivers/vhost/net.c

@@ -170,7 +170,7 @@ static void vhost_net_buf_unproduce(struct vhost_net_virtqueue *nvq)
 	if (nvq->rx_ring && !vhost_net_buf_is_empty(rxq)) {
 		ptr_ring_unconsume(nvq->rx_ring, rxq->queue + rxq->head,
 				   vhost_net_buf_get_size(rxq),
-				   __skb_array_destroy_skb);
+				   tun_ptr_free);
 		rxq->head = rxq->tail = 0;
 	}
 }

include/linux/if_tun.h

@@ -25,6 +25,7 @@ struct ptr_ring *tun_get_tx_ring(struct file *file);
 bool tun_is_xdp_buff(void *ptr);
 void *tun_xdp_to_ptr(void *ptr);
 void *tun_ptr_to_xdp(void *ptr);
+void tun_ptr_free(void *ptr);
 #else
 #include <linux/err.h>
 #include <linux/errno.h>
@@ -50,5 +51,8 @@ static inline void *tun_ptr_to_xdp(void *ptr)
 {
 	return NULL;
 }
+static inline void tun_ptr_free(void *ptr)
+{
+}
 #endif /* CONFIG_TUN */
 #endif /* __IF_TUN_H */