linux-kernel - Re: [PATCH linux-kselftest/test v1] apparmor: add AppArmor KUnit tests for policy unpack

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Date:   Tue, 5 Nov 2019 16:37:16 -0800
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Iurii Zaikin <yzaikin@...gle.com>, shuah <shuah@...nel.org>,
        John Johansen <john.johansen@...onical.com>, jmorris@...ei.org,
        serge@...lyn.com, Alan Maguire <alan.maguire@...cle.com>,
        David Gow <davidgow@...gle.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        "Theodore Ts'o" <tytso@....edu>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-security-module@...r.kernel.org,
        KUnit Development <kunit-dev@...glegroups.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Mike Salvatore <mike.salvatore@...onical.com>
Subject: Re: [PATCH linux-kselftest/test v1] apparmor: add AppArmor KUnit
 tests for policy unpack

On Tue, Nov 5, 2019 at 4:35 PM Brendan Higgins
<brendanhiggins@...gle.com> wrote:
>
> On Wed, Oct 30, 2019 at 11:59 AM Kees Cook <keescook@...omium.org> wrote:
> >
> > On Thu, Oct 17, 2019 at 05:33:56PM -0700, Iurii Zaikin wrote:
> > > On Thu, Oct 17, 2019 at 5:19 PM Brendan Higgins
> > > <brendanhiggins@...gle.com> wrote:
> > >
> > > > +config SECURITY_APPARMOR_TEST
> > > > +       bool "Build KUnit tests for policy_unpack.c"
> > > > +       default n
> >
> > New options already already default n, this can be left off.
> >
> > > > +       depends on KUNIT && SECURITY_APPARMOR
> > > > +       help
> > > >
> > > select SECURITY_APPARMOR ?
> >
> > "select" doesn't enforce dependencies, so just a "depends ..." is
> > correct.
> >
> > > > +       KUNIT_EXPECT_EQ(test, size, TEST_BLOB_DATA_SIZE);
> > > > +       KUNIT_EXPECT_TRUE(test,
> > > > +               memcmp(blob, TEST_BLOB_DATA, TEST_BLOB_DATA_SIZE) == 0);
> > > I think this must be  KUNIT_ASSERT_EQ(test, size, TEST_BLOB_DATA_SIZE);,
> > > otherwise there could be a buffer overflow in memcmp. All tests that
> > > follow such pattern
> >
> > Agreed.
> >
> > > are suspect. Also, not sure about your stylistic preference for
> > > KUNIT_EXPECT_TRUE(test,
> > >                memcmp(blob, TEST_BLOB_DATA, TEST_BLOB_DATA_SIZE) == 0);
> > > vs
> > > KUNIT_EXPECT_EQ(test,
> > >                0,
> > >                memcmp(blob, TEST_BLOB_DATA, TEST_BLOB_DATA_SIZE));
> >
> > I like == 0.
>
> Oh, I almost missed this. I think the *_EQ(...) is better than the
> *_TRUE(...) because the EQ is able to provide more debug information
> if the test fails (otherwise there would really be no point in
> providing all these variants).
>
> Any objections?
>
> Thanks for the catch Iurii!

Wait, nevermind.

Either way is fine because memcmp probably won't show terribly
interesting information in the non-zero case. I'll just leave it the
way Mike wrote it.

Sorry!