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: <sta...@vger.kernel.org> # v3.19+
Signed-off-by: Ian Abbott <abbo...@mev.co.uk>
---
Note: A similar patch will be required for stable v3.16.x, but that
calls cfc_handle_events() instead of comedi_handle_events().
---
drivers/staging/comedi/drivers/dt282x.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/staging/comedi/drivers/dt282x.c
b/drivers/staging/comedi/drivers/dt282x.c
index 3be927f1d3a9..e15e33ed94ae 100644
--- a/drivers/staging/comedi/drivers/dt282x.c
+++ b/drivers/staging/comedi/drivers/dt282x.c
@@ -557,7 +557,8 @@ static irqreturn_t dt282x_interrupt(int irq, void *d)
}
#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);
}
--
2.20.1
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