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staging: comedi: amplc_pci230: fix null pointer deref on interrupt 

The interrupt handler `pci230_interrupt()` causes a null pointer
dereference for a PCI260 card.  There is no analog output subdevice for
a PCI260.  The `dev->write_subdev` subdevice pointer and therefore the
`s_ao` subdevice pointer variable will be `NULL` for a PCI260.  The
following call near the end of the interrupt handler results in the null
pointer dereference for a PCI260:

	comedi_handle_events(dev, s_ao);

Fix it by only calling the above function if `s_ao` is valid.

Note that the other uses of `s_ao` in the calls
`pci230_handle_ao_nofifo(dev, s_ao);` and `pci230_handle_ao_fifo(dev,
s_ao);` will never be reached for a PCI260, so they are safe.

Fixes: 39064f2328 ("staging: comedi: amplc_pci230: use comedi_handle_events()")
Cc: <stable@vger.kernel.org> # v3.19+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2019-06-26 14:17:39 +01:00 committed by Greg Kroah-Hartman
parent 338d963736
commit 7379e6baed
1 changed files with 2 additions and 1 deletions
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3
drivers/staging/comedi/drivers/amplc_pci230.c
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@ -2330,7 +2330,8 @@ static irqreturn_t pci230_interrupt(int irq, void *d)
devpriv->intr_running = false;
spin_unlock_irqrestore(&devpriv->isr_spinlock, irqflags);
comedi_handle_events(dev, s_ao);
if (s_ao)
comedi_handle_events(dev, s_ao);
comedi_handle_events(dev, s_ai);
return IRQ_HANDLED;