Staging: comedi: jr3_pci: Don't ioremap too much space. Check result.

For the JR3/PCI cards, the size of the PCIBAR0 region depends on the
number of channels.  Don't try and ioremap space for 4 channels if the
card has fewer channels.  Also check for ioremap failure.

Thanks to Anders Blomdell for input and Sami Hussein for testing.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/comedi/drivers/jr3_pci.c

@@ -849,8 +849,11 @@ static int jr3_pci_attach(struct comedi_device *dev,
 	}
 
 	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;