linux-kernel - Re: [PATCH 2/2] iio: inkern: add error case in iio_channel

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Date:	Mon, 10 Sep 2012 11:24:08 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	"Kim, Milo" <Milo.Kim@...com>
CC:	Jonathan Cameron <jic23@...nel.org>,
	Jonathan Cameron <jic23@....ac.uk>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] iio: inkern: add error case in iio_channel_get()

On 09/10/2012 10:02 AM, Kim, Milo wrote:
>  The datasheet name is defined in the IIO driver.
>  On the other hand, the adc_channel_label is configured in
>  the platform machine side.
>  If the datasheet name is not matched with any adc_channel_label,
>  the iio_channel_get() should be returned as error for preventing
>  using invalid IIO channel data.
> 
>  Moreover, this patch detects NULL pointer dereference problem at early time.
>  In general, the IIO driver just accesses to any member of the iio_chan_spec
>  in own xxx_read_raw() function.
>  If the iio_chan_spec is invalid pointer, NULL dereference problem may occur
>  such like 'iio_chan_spec->channel' or 'iio_chan_spec->type'.
>  If the iio_channel_get() gets failed in the IIO consumer,
>  then no read_raw() operation proceeds.
> 
> Signed-off-by: Milo(Woogyom) Kim <milo.kim@...com>
> ---
>  drivers/iio/inkern.c |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index 1faa240..a5caf6b 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -136,11 +136,15 @@ struct iio_channel *iio_channel_get(const char *name, const char *channel_name)
>  
>  	channel->indio_dev = c->indio_dev;
>  
> -	if (c->map->adc_channel_label)
> +	if (c->map->adc_channel_label) {
>  		channel->channel =
>  			iio_chan_spec_from_name(channel->indio_dev,
>  						c->map->adc_channel_label);
>  
> +		if (channel->channel == NULL)
> +			return ERR_PTR(-ENODEV);

This introduces a memory leak. You need to free channel before returning.

> +	}
> +
>  	return channel;
>  }
>  EXPORT_SYMBOL_GPL(iio_channel_get);

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