linux-kernel - Re: [PATCH v6 3/5] KVM: selftests: Add atoi_paranoid() to catch errors missed by atoi()

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Message-ID: <Y1lN/YRc2B3KoR+n@google.com>
Date:   Wed, 26 Oct 2022 15:10:53 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     "Wang, Wei W" <wei.w.wang@...el.com>
Cc:     Vipin Sharma <vipinsh@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "andrew.jones@...ux.dev" <andrew.jones@...ux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 3/5] KVM: selftests: Add atoi_paranoid() to catch
 errors missed by atoi()

On Wed, Oct 26, 2022, Wang, Wei W wrote:
> On Saturday, October 22, 2022 5:18 AM, Vipin Sharma wrote:
> > +int atoi_paranoid(const char *num_str)
> > +{
> > +	char *end_ptr;
> > +	long num;
> > +
> > +	errno = 0;
> > +	num = strtol(num_str, &end_ptr, 10);
> 
> Why not use strtoull here?

This intended to be a drop in replacement for atoi(), which allows negative
numbers.

> Negative numbers will result in a huge "unsigned long long" number,
> and this will be captured by your TEST_ASSERT(num >= INT_MIN) below.

As above, we want to allow negative numbers, e.g. memslot_perf_test.c uses '-1'
to indicate "as many slots as possible".

It's unlikely a test will As unlikely as 

> Then we don't need patch 4, I think.

Even if this low level helper disallowed negative numbers, patch 4 still has value
in that the wrappers make the code self-documenting, i.e. makes it very obvious
what input values are allowed.