linux-kernel - Re: [RFC PATCH] iio: ak8975: Make sure chipset is always initialized

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Date:	Fri, 19 Dec 2014 23:16:54 +0100
From:	Hartmut Knaack <knaack.h@....de>
To:	Daniel Baluta <daniel.baluta@...el.com>, jic23@...nel.org
CC:	lars@...afoo.de, pmeerw@...erw.net, gwendal@...omium.org,
	srinivas.pandruvada@...ux.intel.com, beomho.seo@...sung.com,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	octavian.purdila@...el.com
Subject: Re: [RFC PATCH] iio: ak8975: Make sure chipset is always initialized

Daniel Baluta schrieb am 18.12.2014 um 18:16:
> When using ACPI, if acpi_match_device fails then chipset enum will be
> uninitialized and &ak_def_array[chipset] will point to some bad address.
> 
> This fixes the following compilation warning:
> 
> drivers/iio/magnetometer/ak8975.c: In function ‘ak8975_probe’:
> drivers/iio/magnetometer/ak8975.c:788:14: warning: ‘chipset’ may be used
> uninitialized in this function [-Wmaybe-uninitialized]
>   data->def =ak_def_array[chipset];
> 
> Reported-by: Octavian Purdila <octavian.purdila@...el.com>
> Signed-off-by: Daniel Baluta <daniel.baluta@...el.com>
> ---
> This is a RFC because while I'm pretty sure that chipset should be initialized
> with AK_MAX_TYPE in ak8975_match_acpi_device, I am not sure if we can live with
> a NULL return value of ak8975_match_acpi_device. Current implementation ignores
> return value of ak8975_match_acpi_device.
This seems to be the actual problem: these _match_acpi_device functions return
NULL on failure, and this should be checked for.

> 
> The same situation is for kxcjk-1013, bmc150-accel, bmg160 and possible other
> drivers.
> 
>  drivers/iio/magnetometer/ak8975.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
> index 0d10a4b..cdf9e77 100644
> --- a/drivers/iio/magnetometer/ak8975.c
> +++ b/drivers/iio/magnetometer/ak8975.c
> @@ -716,6 +716,7 @@ static const char *ak8975_match_acpi_device(struct device *dev,
>  {
>  	const struct acpi_device_id *id;
>  
> +	*chipset =K_MAX_TYPE;
>  	id =cpi_match_device(dev->driver->acpi_match_table, dev);
>  	if (!id)
>  		return NULL;
> 

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