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From:   Joel Fernandes <joel@joelfernandes.org>
Date:   Thu, 18 Oct 2018 00:08:58 -0700
Message-ID: <CAEXW_YTDWgY3JAeiY0Ti0BBL=iJMcSkR5V7USJYv6UxHiCpN-g@mail.gmail.com>
Subject: Re: [PATCH v3 2/2] selftests/memfd: Add tests for F_SEAL_FS_WRITE seal
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     kernel-team <kernel-team@android.com>,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        Daniel Colascione <dancol@google.com>,
        Minchan Kim <minchan@kernel.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "J. Bruce Fields" <bfields@fieldses.org>,
        Jeff Layton <jlayton@kernel.org>,
        John Stultz <john.stultz@linaro.org>,
        John Reck <jreck@google.com>, linux-fsdevel@vger.kernel.org,
        linux-kselftest <linux-kselftest@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>, marcandre.lureau@redhat.com,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Shuah Khan <shuah@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Todd Kjos <tkjos@google.com>
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On Wed, Oct 17, 2018 at 11:59 PM, Joel Fernandes (Google)
<joel@joelfernandes.org> wrote:
> Add tests to verify sealing memfds with the F_SEAL_FS_WRITE works as
> expected.

I messed the commit message it should be "F_SEAL_FUTURE_WRITE", but
otherwise this
patch itself is good and I'll resend it with the corrected commit
message after further review.

thanks,

 - Joel


> Cc: dancol@google.com
> Cc: minchan@kernel.org
> Reviewed-by: John Stultz <john.stultz@linaro.org>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> ---
>  tools/testing/selftests/memfd/memfd_test.c | 74 ++++++++++++++++++++++
>  1 file changed, 74 insertions(+)
>
> diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
> index 10baa1652fc2..32b207ca7372 100644
> --- a/tools/testing/selftests/memfd/memfd_test.c
> +++ b/tools/testing/selftests/memfd/memfd_test.c
> @@ -692,6 +692,79 @@ static void test_seal_write(void)
>         close(fd);
>  }
>
> +/*
> + * Test SEAL_FUTURE_WRITE
> + * Test whether SEAL_FUTURE_WRITE actually prevents modifications.
> + */
> +static void test_seal_future_write(void)
> +{
> +       int fd;
> +       void *p;
> +
> +       printf("%s SEAL-FUTURE-WRITE\n", memfd_str);
> +
> +       fd = mfd_assert_new("kern_memfd_seal_future_write",
> +                           mfd_def_size,
> +                           MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +
> +       p = mfd_assert_mmap_shared(fd);
> +
> +       mfd_assert_has_seals(fd, 0);
> +       /* Not adding grow/shrink seals makes the future write
> +        * seal fail to get added
> +        */
> +       mfd_fail_add_seals(fd, F_SEAL_FUTURE_WRITE);
> +
> +       mfd_assert_add_seals(fd, F_SEAL_GROW);
> +       mfd_assert_has_seals(fd, F_SEAL_GROW);
> +
> +       /* Should still fail since shrink seal has
> +        * not yet been added
> +        */
> +       mfd_fail_add_seals(fd, F_SEAL_FUTURE_WRITE);
> +
> +       mfd_assert_add_seals(fd, F_SEAL_SHRINK);
> +       mfd_assert_has_seals(fd, F_SEAL_GROW |
> +                                F_SEAL_SHRINK);
> +
> +       /* Now should succeed, also verifies that the seal
> +        * could be added with an existing writable mmap
> +        */
> +       mfd_assert_add_seals(fd, F_SEAL_FUTURE_WRITE);
> +       mfd_assert_has_seals(fd, F_SEAL_SHRINK |
> +                                F_SEAL_GROW |
> +                                F_SEAL_FUTURE_WRITE);
> +
> +       /* read should pass, writes should fail */
> +       mfd_assert_read(fd);
> +       mfd_fail_write(fd);
> +
> +       munmap(p, mfd_def_size);
> +       close(fd);
> +
> +       /* Test adding all seals (grow, shrink, future write) at once */
> +       fd = mfd_assert_new("kern_memfd_seal_future_write2",
> +                           mfd_def_size,
> +                           MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +
> +       p = mfd_assert_mmap_shared(fd);
> +
> +       mfd_assert_has_seals(fd, 0);
> +       mfd_assert_add_seals(fd, F_SEAL_SHRINK |
> +                                F_SEAL_GROW |
> +                                F_SEAL_FUTURE_WRITE);
> +       mfd_assert_has_seals(fd, F_SEAL_SHRINK |
> +                                F_SEAL_GROW |
> +                                F_SEAL_FUTURE_WRITE);
> +
> +       /* read should pass, writes should fail */
> +       mfd_assert_read(fd);
> +       mfd_fail_write(fd);
> +
> +       munmap(p, mfd_def_size);
> +       close(fd);
> +}
> +
>  /*
>   * Test SEAL_SHRINK
>   * Test whether SEAL_SHRINK actually prevents shrinking
> @@ -945,6 +1018,7 @@ int main(int argc, char **argv)
>         test_basic();
>
>         test_seal_write();
> +       test_seal_future_write();
>         test_seal_shrink();
>         test_seal_grow();
>         test_seal_resize();
> --
> 2.19.1.331.ge82ca0e54c-goog
>