Re: [PATCH 04/25] iio:light:st_uvis25 Fix timestamp alignment and prevent data leak.

[Lorenzo Bianconi <lorenzo@kernel.org>]

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> From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> One of a class of bugs pointed out by Lars in a recent review.
> iio_push_to_buffers_with_timestamp assumes the buffer used is aligned
> to the size of the timestamp (8 bytes).  This is not guaranteed in
> this driver which uses an array of smaller elements on the stack.
> As Lars also noted this anti pattern can involve a leak of data to
> userspace and that indeed can happen here.  We close both issues by
> moving to a suitable structure in the iio_priv()
> 
> This data is allocated with kzalloc so no data can leak apart
> from previous readings.
> 
> Fixes: 3025c8688c1e ("iio: light: add support for UVIS25 sensor")
> Reported-by: Lars-Peter Clausen <lars@metafoo.de>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>

Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>

> ---
>  drivers/iio/light/st_uvis25.h      | 5 +++++
>  drivers/iio/light/st_uvis25_core.c | 6 +++---
>  2 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/light/st_uvis25.h b/drivers/iio/light/st_uvis25.h
> index 78bc56aad129..f7027e4c4493 100644
> --- a/drivers/iio/light/st_uvis25.h
> +++ b/drivers/iio/light/st_uvis25.h
> @@ -27,6 +27,11 @@ struct st_uvis25_hw {
>  	struct iio_trigger *trig;
>  	bool enabled;
>  	int irq;
> +	/* Ensure timestamp is naturally aligned */
> +	struct {
> +		u8 chan;
> +		s64 ts;
> +	} scan;
>  };
>  
>  extern const struct dev_pm_ops st_uvis25_pm_ops;
> diff --git a/drivers/iio/light/st_uvis25_core.c b/drivers/iio/light/st_uvis25_core.c
> index d262c254b895..fe1f2dc970c7 100644
> --- a/drivers/iio/light/st_uvis25_core.c
> +++ b/drivers/iio/light/st_uvis25_core.c
> @@ -234,17 +234,17 @@ static const struct iio_buffer_setup_ops st_uvis25_buffer_ops = {
>  
>  static irqreturn_t st_uvis25_buffer_handler_thread(int irq, void *p)
>  {
> -	u8 buffer[ALIGN(sizeof(u8), sizeof(s64)) + sizeof(s64)];
>  	struct iio_poll_func *pf = p;
>  	struct iio_dev *iio_dev = pf->indio_dev;
>  	struct st_uvis25_hw *hw = iio_priv(iio_dev);
>  	int err;
>  
> -	err = regmap_read(hw->regmap, ST_UVIS25_REG_OUT_ADDR, (int *)buffer);
> +	err = regmap_read(hw->regmap, ST_UVIS25_REG_OUT_ADDR,
> +			  (unsigned int *)&hw->scan.chan);
>  	if (err < 0)
>  		goto out;
>  
> -	iio_push_to_buffers_with_timestamp(iio_dev, buffer,
> +	iio_push_to_buffers_with_timestamp(iio_dev, &hw->scan,
>  					   iio_get_time_ns(iio_dev));
>  
>  out:
> -- 
> 2.26.2
> 

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