Commit 71ba17c0 authored by Ian Abbott's avatar Ian Abbott Committed by Kleber Sacilotto de Souza

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

BugLink: https://bugs.launchpad.net/bugs/1838467

commit b8336be6 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 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: <stable@vger.kernel.org> # v3.19+
Signed-off-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarConnor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: default avatarKhalid Elmously <khalid.elmously@canonical.com>
parent 4a5d82ca
...@@ -553,6 +553,7 @@ static irqreturn_t dt282x_interrupt(int irq, void *d) ...@@ -553,6 +553,7 @@ static irqreturn_t dt282x_interrupt(int irq, void *d)
} }
#endif #endif
comedi_handle_events(dev, s); comedi_handle_events(dev, s);
if (s_ao)
comedi_handle_events(dev, s_ao); comedi_handle_events(dev, s_ao);
return IRQ_RETVAL(handled); return IRQ_RETVAL(handled);
......
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