2024-02-28 21:08:32

by David Lechner

Subject: Re: [PATCH v4 3/8] iio: core: NULLify private pointer when there is no private data

On Wed, Feb 28, 2024 at 2:50 PM Andy Shevchenko
<[email protected]> wrote:
>
> In iio_device_alloc() when size of the private data is 0,
> the private pointer is calculated to behind the valid data.
> NULLify it for good.
>
> Fixes: 6d4ebd565d15 ("iio: core: wrap IIO device into an iio_dev_opaque object")
> Signed-off-by: Andy Shevchenko <[email protected]>
> ---
> drivers/iio/industrialio-core.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 4302093b92c7..bd305fa87093 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -1654,8 +1654,12 @@ struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv)
> return NULL;
>
> indio_dev = &iio_dev_opaque->indio_dev;
> - indio_dev->priv = (char *)iio_dev_opaque +
> - ALIGN(sizeof(struct iio_dev_opaque), IIO_DMA_MINALIGN);
> +
> + if (sizeof_priv)
> + indio_dev->priv = (char *)iio_dev_opaque +
> + ALIGN(sizeof(struct iio_dev_opaque), IIO_DMA_MINALIGN);
> + else
> + indio_dev->priv = NULL;

Do we actually need the else branch here since we use kzalloc() and
therefore indio_dev->priv should already be NULL?

>
> indio_dev->dev.parent = parent;
> indio_dev->dev.type = &iio_device_type;
> --
> 2.43.0.rc1.1.gbec44491f096
>
>

2024-02-28 21:55:41

by Andy Shevchenko

Subject: Re: [PATCH v4 3/8] iio: core: NULLify private pointer when there is no private data

On Wed, Feb 28, 2024 at 03:06:42PM -0600, David Lechner wrote:
> On Wed, Feb 28, 2024 at 2:50 PM Andy Shevchenko
> <[email protected]> wrote:

..

> > - indio_dev->priv = (char *)iio_dev_opaque +
> > - ALIGN(sizeof(struct iio_dev_opaque), IIO_DMA_MINALIGN);
> > +
> > + if (sizeof_priv)
> > + indio_dev->priv = (char *)iio_dev_opaque +
> > + ALIGN(sizeof(struct iio_dev_opaque), IIO_DMA_MINALIGN);
> > + else
> > + indio_dev->priv = NULL;
>
> Do we actually need the else branch here since we use kzalloc() and
> therefore indio_dev->priv should already be NULL?

This is more robust, but I'm okay to drop this. Up to Jonathan.

--
With Best Regards,
Andy Shevchenko

2024-03-03 12:56:50

by Jonathan Cameron

Subject: Re: [PATCH v4 3/8] iio: core: NULLify private pointer when there is no private data

On Wed, 28 Feb 2024 23:36:43 +0200
Andy Shevchenko <[email protected]> wrote:

> On Wed, Feb 28, 2024 at 03:06:42PM -0600, David Lechner wrote:
> > On Wed, Feb 28, 2024 at 2:50 PM Andy Shevchenko
> > <[email protected]> wrote:
>
> ...
>
> > > - indio_dev->priv = (char *)iio_dev_opaque +
> > > - ALIGN(sizeof(struct iio_dev_opaque), IIO_DMA_MINALIGN);
> > > +
> > > + if (sizeof_priv)
> > > + indio_dev->priv = (char *)iio_dev_opaque +
> > > + ALIGN(sizeof(struct iio_dev_opaque), IIO_DMA_MINALIGN);
> > > + else
> > > + indio_dev->priv = NULL;
> >
> > Do we actually need the else branch here since we use kzalloc() and
> > therefore indio_dev->priv should already be NULL?
>
> This is more robust, but I'm okay to drop this. Up to Jonathan.
>

Given the allocation is just above here fine to drop the else in this
I think.