linux-kernel - Re: [PATCH] bpf: Fix IMA test

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Message-ID: <CAEf4BzaQTcDgvH5a9E3crkJENxQnOOjR=TdTmFwUGk4g3=oF_w@mail.gmail.com>
Date:   Wed, 8 Mar 2023 11:17:07 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Roberto Sassu <roberto.sassu@...weicloud.com>
Cc:     andrii@...nel.org, mykolal@...com, ast@...nel.org,
        daniel@...earbox.net, martin.lau@...ux.dev, song@...nel.org,
        yhs@...com, john.fastabend@...il.com, kpsingh@...nel.org,
        sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org,
        shuah@...nel.org, bpf@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org, mattbobrowski@...gle.com,
        zohar@...ux.ibm.com, Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH] bpf: Fix IMA test

On Wed, Mar 8, 2023 at 2:41 AM Roberto Sassu
<roberto.sassu@...weicloud.com> wrote:
>
> On Wed, 2023-03-08 at 11:37 +0100, Roberto Sassu wrote:
> > From: Roberto Sassu <roberto.sassu@...wei.com>
>
> The title should have been selftests/bpf: ...
>
> Will send a new version once I get the test result.

I fixed up prefix and Reported-by tag, pushed to bpf-next. Thanks for the fix!

>
> Roberto
>
> > Commit 62622dab0a28 ("ima: return IMA digest value only when IMA_COLLECTED
> > flag is set") caused bpf_ima_inode_hash() to refuse to give non-fresh
> > digests. IMA test #3 assumed the old behavior, that bpf_ima_inode_hash()
> > still returned also non-fresh digests.
> >
> > Correct the test by accepting both cases. If the samples returned are 1,
> > assume that the commit above is applied and that the returned digest is
> > fresh. If the samples returned are 2, assume that the commit above is not
> > applied, and check both the non-fresh and fresh digest.
> >
> > Fixes: 62622dab0a28 ("ima: return IMA digest value only when IMA_COLLECTED flag is set")
> > Reported by: David Vernet <void@...ifault.com>
> > Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> > ---
> >  .../selftests/bpf/prog_tests/test_ima.c       | 29 ++++++++++++++-----
> >  1 file changed, 21 insertions(+), 8 deletions(-)
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/test_ima.c b/tools/testing/selftests/bpf/prog_tests/test_ima.c
> > index b13feceb38f..810b14981c2 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/test_ima.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/test_ima.c
> > @@ -70,7 +70,7 @@ void test_test_ima(void)
> >       u64 bin_true_sample;
> >       char cmd[256];
> >
> > -     int err, duration = 0;
> > +     int err, duration = 0, fresh_digest_idx = 0;
> >       struct ima *skel = NULL;
> >
> >       skel = ima__open_and_load();
> > @@ -129,7 +129,15 @@ void test_test_ima(void)
> >       /*
> >        * Test #3
> >        * - Goal: confirm that bpf_ima_inode_hash() returns a non-fresh digest
> > -      * - Expected result: 2 samples (/bin/true: non-fresh, fresh)
> > +      * - Expected result:
> > +      *   1 sample (/bin/true: fresh) if commit 62622dab0a28 applied
> > +      *   2 samples (/bin/true: non-fresh, fresh) if commit 62622dab0a28 is
> > +      *     not applied
> > +      *
> > +      * If commit 62622dab0a28 ("ima: return IMA digest value only when
> > +      * IMA_COLLECTED flag is set") is applied, bpf_ima_inode_hash() refuses
> > +      * to give a non-fresh digest, hence the correct result is 1 instead of
> > +      * 2.
> >        */
> >       test_init(skel->bss);
> >
> > @@ -144,13 +152,18 @@ void test_test_ima(void)
> >               goto close_clean;
> >
> >       err = ring_buffer__consume(ringbuf);
> > -     ASSERT_EQ(err, 2, "num_samples_or_err");
> > -     ASSERT_NEQ(ima_hash_from_bpf[0], 0, "ima_hash");
> > -     ASSERT_NEQ(ima_hash_from_bpf[1], 0, "ima_hash");
> > -     ASSERT_EQ(ima_hash_from_bpf[0], bin_true_sample, "sample_equal_or_err");
> > +     ASSERT_GE(err, 1, "num_samples_or_err");
> > +     if (err == 2) {
> > +             ASSERT_NEQ(ima_hash_from_bpf[0], 0, "ima_hash");
> > +             ASSERT_EQ(ima_hash_from_bpf[0], bin_true_sample,
> > +                       "sample_equal_or_err");
> > +             fresh_digest_idx = 1;
> > +     }
> > +
> > +     ASSERT_NEQ(ima_hash_from_bpf[fresh_digest_idx], 0, "ima_hash");
> >       /* IMA refreshed the digest. */
> > -     ASSERT_NEQ(ima_hash_from_bpf[1], bin_true_sample,
> > -                "sample_different_or_err");
> > +     ASSERT_NEQ(ima_hash_from_bpf[fresh_digest_idx], bin_true_sample,
> > +                "sample_equal_or_err");
> >
> >       /*
> >        * Test #4
>