--- 59a61068f96612c825b744b7e22274699ca85704
+++ 1d6385a52dccbd2947d3cf8579491e2ea263d261
@@ -856,8 +856,11 @@ static int jr3_pci_attach(struct comedi_
 	}
 
 	devpriv->pci_enabled = 1;
-	devpriv->iobase =
-	    ioremap(pci_resource_start(card, 0), sizeof(struct jr3_t));
+	devpriv->iobase = ioremap(pci_resource_start(card, 0),
+			offsetof(struct jr3_t, channel[devpriv->n_channels]));
+	if (!devpriv->iobase)
+		return -ENOMEM;
+
 	result = alloc_subdevices(dev, devpriv->n_channels);
 	if (result < 0)
 		goto out;