linux-kernel - Re: [PATCH v7 3/5] KVM: selftests: Add atoi_paranoid() to catch errors missed by atoi()

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Date:   Mon, 31 Oct 2022 12:44:04 -0700
From:   Vipin Sharma <vipinsh@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     pbonzini@...hat.com, dmatlack@...gle.com, andrew.jones@...ux.dev,
        wei.w.wang@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 3/5] KVM: selftests: Add atoi_paranoid() to catch
 errors missed by atoi()

On Mon, Oct 31, 2022 at 12:17 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Mon, Oct 31, 2022, Vipin Sharma wrote:
> > atoi() doesn't detect errors. There is no way to know that a 0 return
> > is correct conversion or due to an error.
> >
> > Introduce atoi_paranoid() to detect errors and provide correct
> > conversion. Replace all atoi() calls with atoi_paranoid().
> > diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> > index 6d23878bbfe1..ec0f070a6f21 100644
> > --- a/tools/testing/selftests/kvm/lib/test_util.c
> > +++ b/tools/testing/selftests/kvm/lib/test_util.c
> > @@ -334,3 +334,22 @@ long get_run_delay(void)
> >
> >       return val[1];
> >  }
> > +
> > +int atoi_paranoid(const char *num_str)
> > +{
> > +     char *end_ptr;
> > +     long num;
> > +
> > +     errno = 0;
> > +     num = strtol(num_str, &end_ptr, 10);
>
> I take back my review.  This forces specifying params in decimal, e.g. a large
> hex number yields:
>
>   strtol("0xffffffffff") failed to parse trailing characters "xffffffffff".
>
> Obviously I'm intentionally being a bad user in this particular case, but there
> will inevitably be tests that want to take hex input, e.g. an x86 test that takes
> an MSR index would definitely want hex input.
>
> Looking through all selftests, I don't think there are existing cases that would
> likely want hex, but it's trivial to support since strtol() will autodetect the
> format if the base is '0', i.e.

atoi_paranoid() replaced atoi() which only works for base 10. I was
keeping it similar.

I'll wait a couple of days for any other feedback and send v8.

>
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index 210e98a49a83..8c37cfa12edc 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -341,7 +341,7 @@ int atoi_paranoid(const char *num_str)
>         long num;
>
>         errno = 0;
> -       num = strtol(num_str, &end_ptr, 10);
> +       num = strtol(num_str, &end_ptr, 0);
>         TEST_ASSERT(!errno, "strtol(\"%s\") failed", num_str);
>         TEST_ASSERT(num_str != end_ptr,
>                     "strtol(\"%s\") didn't find a valid integer.\n", num_str);