From: Ian Abbott abbotti@mev.co.uk
commit b8336be66dec06bef518030a0df9847122053ec5 upstream.
The interrupt handler `dt282x_interrupt()` causes a null pointer dereference for those supported boards that have no analog output support. For these boards, `dev->write_subdev` will be `NULL` and therefore the `s_ao` subdevice pointer variable will be `NULL`. In that case, the following call near the end of the interrupt handler results in a null pointer dereference:
comedi_handle_events(dev, s_ao);
Fix it by only calling the above function if `s_ao` is valid.
(There are other uses of `s_ao` by the interrupt handler that may or may not be reached depending on values of hardware registers. Trust that they are reliable for now.)
Note: commit 4f6f009b204f ("staging: comedi: dt282x: use comedi_handle_events()") propagates an earlier error from commit f21c74fa4cfe ("staging: comedi: dt282x: use cfc_handle_events()").
Fixes: 4f6f009b204f ("staging: comedi: dt282x: 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
--- drivers/staging/comedi/drivers/dt282x.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/staging/comedi/drivers/dt282x.c +++ b/drivers/staging/comedi/drivers/dt282x.c @@ -557,7 +557,8 @@ static irqreturn_t dt282x_interrupt(int } #endif comedi_handle_events(dev, s); - comedi_handle_events(dev, s_ao); + if (s_ao) + comedi_handle_events(dev, s_ao);
return IRQ_RETVAL(handled); }