Re: [PATCH v3 03/10] iio: bmc150-accel-core: Fix unsafe buffer attributes

[Jonathan Cameron]

On Mon, 3 Oct 2022 11:11:12 +0300
Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote:

> The iio_triggered_buffer_setup_ext() was changed by
> commit 15097c7a1adc ("iio: buffer: wrap all buffer attributes into iio_dev_attr")
> to silently expect that all attributes given in buffer_attrs array are
> device-attributes. This expectation was not forced by the API - and some
> drivers did register attributes created by IIO_CONST_ATTR().
> 
> The added attribute "wrapping" does not copy the pointer to stored
> string constant and when the sysfs file is read the kernel will access
> to invalid location.
> 
> Change the IIO_CONST_ATTRs from the driver to IIO_DEVICE_ATTR in order
> to prevent the invalid memory access.
> 
> Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
> Fixes: 15097c7a1adc ("iio: buffer: wrap all buffer attributes into iio_dev_attr")
Applied to the fixes-togreg branch of iio.git and marked for stable.

Thanks,

Jonathan

> 
> ---
> 
> v2 => v3:
> Split change to own patch for simpler fix backporting.
> ---
>  drivers/iio/accel/bmc150-accel-core.c | 23 ++++++++++++++++++-----
>  1 file changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
> index 57e8a8350cd1..92f8b139acce 100644
> --- a/drivers/iio/accel/bmc150-accel-core.c
> +++ b/drivers/iio/accel/bmc150-accel-core.c
> @@ -925,17 +925,30 @@ static const struct iio_chan_spec_ext_info bmc150_accel_ext_info[] = {
>  	{ }
>  };
>  
> -static IIO_CONST_ATTR(hwfifo_watermark_min, "1");
> -static IIO_CONST_ATTR(hwfifo_watermark_max,
> -		      __stringify(BMC150_ACCEL_FIFO_LENGTH));
> +static ssize_t hwfifo_watermark_min_show(struct device *dev,
> +					 struct device_attribute *attr,
> +					 char *buf)
> +{
> +	return sysfs_emit(buf, "%s\n", "1");
> +}
> +
> +static ssize_t hwfifo_watermark_max_show(struct device *dev,
> +					 struct device_attribute *attr,
> +					 char *buf)
> +{
> +	return sysfs_emit(buf, "%s\n", __stringify(BMC150_ACCEL_FIFO_LENGTH));
> +}
> +
> +static IIO_DEVICE_ATTR_RO(hwfifo_watermark_min, 0);
> +static IIO_DEVICE_ATTR_RO(hwfifo_watermark_max, 0);
>  static IIO_DEVICE_ATTR(hwfifo_enabled, S_IRUGO,
>  		       bmc150_accel_get_fifo_state, NULL, 0);
>  static IIO_DEVICE_ATTR(hwfifo_watermark, S_IRUGO,
>  		       bmc150_accel_get_fifo_watermark, NULL, 0);
>  
>  static const struct attribute *bmc150_accel_fifo_attributes[] = {
> -	&iio_const_attr_hwfifo_watermark_min.dev_attr.attr,
> -	&iio_const_attr_hwfifo_watermark_max.dev_attr.attr,
> +	&iio_dev_attr_hwfifo_watermark_min.dev_attr.attr,
> +	&iio_dev_attr_hwfifo_watermark_max.dev_attr.attr,
>  	&iio_dev_attr_hwfifo_watermark.dev_attr.attr,
>  	&iio_dev_attr_hwfifo_enabled.dev_attr.attr,
>  	NULL,