Commit a1fcfe09 authored by Ian Abbott's avatar Ian Abbott Committed by Greg Kroah-Hartman

staging: comedi: dt282x: fix a null pointer deref on interrupt

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.)

commit 4f6f009b ("staging: comedi: dt282x: use comedi_handle_events()")
propagates an earlier error from
commit f21c74fa ("staging: comedi: dt282x: use cfc_handle_events()").

Fixes: 4f6f009b ("staging: comedi: dt282x: use comedi_handle_events()")
Cc: <> # v3.19+
Signed-off-by: default avatarIan Abbott <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 769b7aa4
......@@ -566,7 +566,8 @@ static irqreturn_t dt282x_interrupt(int irq, void *d)
comedi_handle_events(dev, s);
comedi_handle_events(dev, s_ao);
if (s_ao)
comedi_handle_events(dev, s_ao);
return IRQ_RETVAL(handled);
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