Re: [PATCH] iio: adc: meson-saradc: use NULL instead of 0 for pointer

[Paolo Cretaro]

Il 04/06/2017 15:32, Martin Blumenstingl ha scritto:
> Hi Paolo, Hi Jonathan,
>
> On Sat, Jun 3, 2017 at 10:52 AM, Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
> > On Sun, 28 May 2017 23:17:57 +0200
> > Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx> wrote:
> >
> > > Hi Paolo, Hi Jonathan,
> > >
> > > On Sun, May 28, 2017 at 4:43 PM, Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
> > > > On Sun, 28 May 2017 13:24:38 +0200
> > > > Paolo Cretaro <paolocretaro@xxxxxxxxx> wrote:
> > > >
> > > > > Fix sparse warning: Using plain integer as NULL pointer
> > > > >
> > > > > Signed-off-by: Paolo Cretaro <paolocretaro@xxxxxxxxx>
> > > > This looks fine to me, but ideally you should always try to include
> > > > the driver author - particularly in the case of patches to a recent
> > > > driver such as this one.
> > > >
> > > > To that end I've cc'd Martin.
> > > thanks for spotting this (and providing a patch to fix it)
> > > this looks good to me, so:
> > > Acked-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> > >
> > > if you can wait until next weekend then I can also test this on real hardware.
> > I've applied it to the togreg branch of iio.git but as that always goes out
> > as testing for at least a few days first (which I will happily rebase) give
> > me a shout if anything goes wrong!
> I have tested this on actual hardware and it seems that there's a bug
> in the meson-saradc driver (before and after this patch):
> if there are still "old" values in the FIFO then the driver currently
> crashes because regmap_read (regmap_mmio_read in case of the
> meson-saradc driver to be precise) de-references the "value" pointer
> (the parameter which we're trying to clean up here) -> this leads to a
> NULL de-reference. this happens regardless of whether we are passing
> "0" or "NULL"
>
> I posted a patch which fixes the crash - and as a bonus this should
> also fix the sparse warning reported by Paolo:
> http://lists.infradead.org/pipermail/linux-amlogic/2017-June/003863.html
Nice, thanks!

Paolo
> > Jonathan
> > > > Jonathan
> > > > > ---
> > > > >   drivers/iio/adc/meson_saradc.c | 2 +-
> > > > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
> > > > > index 81cd39a57fe3..fb3f67a9ae1f 100644
> > > > > --- a/drivers/iio/adc/meson_saradc.c
> > > > > +++ b/drivers/iio/adc/meson_saradc.c
> > > > > @@ -481,7 +481,7 @@ static void meson_sar_adc_clear_fifo(struct iio_dev *indio_dev)
> > > > >                if (!meson_sar_adc_get_fifo_count(indio_dev))
> > > > >                        break;
> > > > >
> > > > > -             regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, 0);
> > > > > +             regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, NULL);
> > > > >        }
> > > > >   }
> > >
> > > Regards,
> > > Martin