linux-kernel - Re: [PATCH] iio: hmc5843_spi: fix a NULL pointer dereference

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Date:   Sun, 10 Mar 2019 10:26:16 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Kangjie Lu <kjlu@....edu>
Cc:     pakki001@....edu, Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: hmc5843_spi: fix a NULL pointer dereference

On Sat,  9 Mar 2019 12:56:27 -0600
Kangjie Lu <kjlu@....edu> wrote:

> In case devm_regmap_init_spi fails and returns NULL, the fix
> returns an error to avoid NULL pointer dereference
> 
> Signed-off-by: Kangjie Lu <kjlu@....edu>

Hi.

The fix is good, but please do the same for the i2c element of
the driver. I'd like them both in a single patch as it's exactly
the same issue in the same driver.

Minor comment inline on how I think it could be a tiny bit
nicer.

Thanks,

Jonathan

> ---
>  drivers/iio/magnetometer/hmc5843_spi.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/magnetometer/hmc5843_spi.c b/drivers/iio/magnetometer/hmc5843_spi.c
> index 535f03a70d63..15e2f7cbb3b5 100644
> --- a/drivers/iio/magnetometer/hmc5843_spi.c
> +++ b/drivers/iio/magnetometer/hmc5843_spi.c
> @@ -59,6 +59,12 @@ static int hmc5843_spi_probe(struct spi_device *spi)
>  {
>  	int ret;
>  	const struct spi_device_id *id = spi_get_device_id(spi);
> +	struct regmap *devm_regmap = devm_regmap_init_spi(spi,
> +			&hmc5843_spi_regmap_config);
Split this into the variable instantiation and the assignment.
That will let you (I think) avoid the nasty alignement.
Also, no need to have the devm_ prefix on the variable name.

	struct regmap *regmap;

	regmap = devm_regmap_init(spi, &hmc5843_spi_regmap_config);

> +
> +	if (IS_ERR(devm_regmap))
> +		return PTR_ERR(devm_regmap);
> +
>  
>  	spi->mode = SPI_MODE_3;
>  	spi->max_speed_hz = 8000000;
> @@ -68,7 +74,7 @@ static int hmc5843_spi_probe(struct spi_device *spi)
>  		return ret;
>  
>  	return hmc5843_common_probe(&spi->dev,
> -			devm_regmap_init_spi(spi, &hmc5843_spi_regmap_config),
> +			devm_regmap,
>  			id->driver_data, id->name);
>  }
>