staging: comedi: amplc_pc236: fix invalid register access during detach

commit aaeb61a97b7159ebe30b18a422d04eeabfa8790b upstream.

`pc236_detach()` is called by the comedi core if it attempted to attach
a device and failed.  `pc236_detach()` calls `pc236_intr_disable()` if
the comedi device private data pointer (`devpriv`) is non-null.  This
test is insufficient as `pc236_intr_disable()` accesses hardware
registers and the attach routine may have failed before it has saved
their I/O base addresses.

Fix it by checking `dev->iobase` is non-zero before calling
`pc236_intr_disable()` as that means the I/O base addresses have been
saved and the hardware registers can be accessed.  It also implies the
comedi device private data pointer is valid, so there is no need to
check it.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/amplc_pc236.c b/drivers/staging/comedi/drivers/amplc_pc236.c
index f50287903038bb22772c1c99522c69078fc638c0..cfbb83b9526a10d79f9b07702ad3cfa3a675abd8 100644 (file)
--- a/drivers/staging/comedi/drivers/amplc_pc236.c
+++ b/drivers/staging/comedi/drivers/amplc_pc236.c
@@ -577,10 +577,9 @@ static int __devinit pc236_attach_pci(struct comedi_device *dev,
 
 static void pc236_detach(struct comedi_device *dev)
 {
-       struct pc236_private *devpriv = dev->private;
        struct pci_dev *pcidev = comedi_to_pci_dev(dev);
 
-       if (devpriv)
+       if (dev->iobase)
                pc236_intr_disable(dev);
        if (dev->irq)
                free_irq(dev->irq, dev);