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

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Date:	Wed, 3 Sep 2014 18:14:20 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Darren Hart <dvhart@...radead.org>
Cc:	Frans Klaver <fransklaver@...il.com>,
	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
Subject: Re: [PATCH] eeepc-laptop: remove possible use of uninitialized value

On Wed, Sep 03, 2014 at 05:49:47PM -0700, Darren Hart wrote:
> 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?

Just return the value of set_acpi() and you should be fine.

thanks,

greg k-h
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