linux-kernel - Re: [PATCH] eeepc-laptop: remove possible use of uninitialized value

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Date:	Wed, 3 Sep 2014 17:49:47 -0700
From:	Darren Hart <dvhart@...radead.org>
To:	Frans Klaver <fransklaver@...il.com>
Cc:	Corentin Chary <corentin.chary@...il.com>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	acpi4asus-user@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] eeepc-laptop: remove possible use of uninitialized value

On Thu, Sep 04, 2014 at 12:53:25AM +0200, Frans Klaver wrote:
> In store_sys_acpi, if count equals zero, or parse_arg()s sscanf call
> fails, 'value' remains possibly uninitialized. In that case 'value'
> shouldn't be used to produce the store_sys_acpi()s return value.
> 
> Only test the return value of set_acpi() if we can actually call it.
> Return rv otherwise.
> 
> Signed-off-by: Frans Klaver <fransklaver@...il.com>
> ---
>  drivers/platform/x86/eeepc-laptop.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/platform/x86/eeepc-laptop.c b/drivers/platform/x86/eeepc-laptop.c
> index bd533c2..41f12ba 100644
> --- a/drivers/platform/x86/eeepc-laptop.c
> +++ b/drivers/platform/x86/eeepc-laptop.c
> @@ -279,10 +279,10 @@ static ssize_t store_sys_acpi(struct device *dev, int cm,
>  	int rv, value;
>  
>  	rv = parse_arg(buf, count, &value);
> -	if (rv > 0)
> -		value = set_acpi(eeepc, cm, value);

That was rather horrible wasn't it? :-)

> -	if (value < 0)
> -		return -EIO;
> +	if (rv > 0) {
> +		if (set_acpi(eeepc, cm, value) < 0)
> +			return -EIO;

Is there a compelling reason not to propogate the return code of set_acpi?
(ENODEV specifically). I see -EIO in Documentation/filesystems/sysfs.txt, but
it's used by default if the show() pointer is NULL (for example), but otherwise
propogates the error.

Specifically it states:

- show() or store() can always return errors. If a bad value comes
  through, be sure to return an error.

Greg, does this need to be -EIO? or is returning someting like ENODEV preferable
if it more accurately reflects the error?

-- 
Darren Hart
Intel Open Source Technology Center
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