linux-kernel - Re: [PATCH 1/3] s390/cpufeature: rework to allow more than only hwcap bits

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Date:   Tue, 12 Jul 2022 21:27:53 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc:     Steffen Eiden <seiden@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, nrb@...ux.ibm.com
Subject: Re: [PATCH 1/3] s390/cpufeature: rework to allow more than only
 hwcap bits

On Tue, Jul 12, 2022 at 06:46:19PM +0200, Claudio Imbrenda wrote:
> > +int cpu_have_feature(unsigned int num)
> > +{
> > +	struct s390_cpu_feature *feature;
> > +
> > +	feature = &s390_cpu_features[num];
> 
> I would put some check to make sure you are going past the end of the
> array. 
> 
> Maybe something like
> 
> if (num >= MAX_CPU_FEATURES) {
> 	WARN(1, "Invalid feature %d", num);
> 	return 0;

That makes sense. I would go for a simple

	if (WARN_ON_ONCE(num >= MAX_CPU_FEATURES))
		return 0;