linux-kernel - Re: [PATCH] iio: adc: MCP3564: fix calib_bias and calib

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Date:   Mon, 4 Dec 2023 09:28:02 +0000
From:   <Marius.Cristea@...rochip.com>
To:     <jic23@...nel.org>, <javier.carrasco.cruz@...il.com>,
        <lars@...afoo.de>
CC:     <linux-kernel@...r.kernel.org>, <linux-iio@...r.kernel.org>
Subject: Re: [PATCH] iio: adc: MCP3564: fix calib_bias and calib_scale range
 checks

Hi Javier Carrasco,

   Thank you for looking over the driver, for spotting and reporting
the bug. Your fix is OK.

Reviewed-by: Marius Cristea <marius.cristea@...rochip.com>

Thanks,
Marius

On Fri, 2023-12-01 at 10:48 +0100, Javier Carrasco wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
> 
> The current implementation uses the AND (&&) operator to check if the
> value to write for IIO_CHAN_INFO_CALIBBIAS and
> IIO_CHAN_INFO_CALIBSCALE
> is within the valid ranges.
> The evaluated values are the lower and upper limits of the ranges,
> so this operation always evaluates to false.
> 
> The OR (||) operator must be used instead.
> 
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.com>
> ---
> This bug has been found when looking for use cases of IIO_AVAIL_RANGE
> and the fix could not be tested with real hardware. The issue and its
> soulution are rather simple, but still some testing and confirmation
> would be welcome.
> ---
>  drivers/iio/adc/mcp3564.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/adc/mcp3564.c b/drivers/iio/adc/mcp3564.c
> index e3f1de5fcc5a..d5fb1cae8aeb 100644
> --- a/drivers/iio/adc/mcp3564.c
> +++ b/drivers/iio/adc/mcp3564.c
> @@ -918,7 +918,7 @@ static int mcp3564_write_raw(struct iio_dev
> *indio_dev,
>                 mutex_unlock(&adc->lock);
>                 return ret;
>         case IIO_CHAN_INFO_CALIBBIAS:
> -               if (val < mcp3564_calib_bias[0] && val >
> mcp3564_calib_bias[2])
> +               if (val < mcp3564_calib_bias[0] || val >
> mcp3564_calib_bias[2])
>                         return -EINVAL;
> 
>                 mutex_lock(&adc->lock);
> @@ -928,7 +928,7 @@ static int mcp3564_write_raw(struct iio_dev
> *indio_dev,
>                 mutex_unlock(&adc->lock);
>                 return ret;
>         case IIO_CHAN_INFO_CALIBSCALE:
> -               if (val < mcp3564_calib_scale[0] && val >
> mcp3564_calib_scale[2])
> +               if (val < mcp3564_calib_scale[0] || val >
> mcp3564_calib_scale[2])
>                         return -EINVAL;
> 
>                 if (adc->calib_scale == val)
> 
> ---
> base-commit: 994d5c58e50e91bb02c7be4a91d5186292a895c8
> change-id: 20231201-mcp3564_range_checks-221708838130
> 
> Best regards,
> --
> Javier Carrasco <javier.carrasco.cruz@...il.com>
>