Re: [PATCH v6 13/14] platform/x86: wmi: create character devices when requested by drivers

[Alan Cox]

On Tue, 10 Oct 2017 19:24:11 +0000
<Mario.Limonciello@xxxxxxxx> wrote:

> > -----Original Message-----
> > From: Pali RohÃr [mailto:pali.rohar@xxxxxxxxx]
> > Sent: Tuesday, October 10, 2017 2:12 PM
> > To: Limonciello, Mario <Mario_Limonciello@xxxxxxxx>
> > Cc: dvhart@xxxxxxxxxxxxx; Andy Shevchenko <andy.shevchenko@xxxxxxxxx>;
> > LKML <linux-kernel@xxxxxxxxxxxxxxx>; platform-driver-x86@xxxxxxxxxxxxxxx;
> > Andy Lutomirski <luto@xxxxxxxxxx>; quasisec@xxxxxxxxxx; rjw@xxxxxxxxxxxxx;
> > mjg59@xxxxxxxxxx; hch@xxxxxx; Greg KH <greg@xxxxxxxxx>
> > Subject: Re: [PATCH v6 13/14] platform/x86: wmi: create character devices when
> > requested by drivers
> > 
> > On Monday 09 October 2017 17:51:51 Mario Limonciello wrote:  
> > > +	/* make sure we're not calling a higher instance than exists*/
> > > +	if (_IOC_NR(cmd) > wblock->gblock.instance_count - 1)
> > > +		return -EINVAL;  
> > 
> > Is this condition really working? instance_count is unsigned, cmd is
> > also unsigned... and when instance_count is zero, then IIRC error would
> > not be thrown.
> >   
> 
> But instance count can't be zero.  MOF would fall apart with a zero instance count.
> If a broken BIOS was shipped with an instance count of zero bigger problems would
> have happened.

Maybe but you can still write the test correctly using >= instead.

Alan