gve: Add NULL pointer checks when freeing irqs.

When freeing notification blocks, we index priv->msix_vectors.
If we failed to allocate priv->msix_vectors (see abort_with_msix_vectors)
this could lead to a NULL pointer dereference if the driver is unloaded.

Fixes: 893ce44d ("gve: Add basic driver framework for Compute Engine Virtual NIC")
Signed-off-by: David Awogbemila <awogbemila@google.com>
Acked-by: Willem de Brujin <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/google/gve/gve_main.c

@@ -301,6 +301,7 @@ static void gve_free_notify_blocks(struct gve_priv *priv)
 {
 	int i;
 
+	if (priv->msix_vectors) {
 		/* Free the irqs */
 		for (i = 0; i < priv->num_ntfy_blks; i++) {
 			struct gve_notify_block *block = &priv->ntfy_blocks[i];
@@ -310,11 +311,12 @@ static void gve_free_notify_blocks(struct gve_priv *priv)
 					      NULL);
 			free_irq(priv->msix_vectors[msix_idx].vector, block);
 		}
+		free_irq(priv->msix_vectors[priv->mgmt_msix_idx].vector, priv);
+	}
 	dma_free_coherent(&priv->pdev->dev,
 			  priv->num_ntfy_blks * sizeof(*priv->ntfy_blocks),
 			  priv->ntfy_blocks, priv->ntfy_block_bus);
 	priv->ntfy_blocks = NULL;
-	free_irq(priv->msix_vectors[priv->mgmt_msix_idx].vector, priv);
 	pci_disable_msix(priv->pdev);
 	kvfree(priv->msix_vectors);
 	priv->msix_vectors = NULL;