linux-kernel - Re: [PATCH v5 4/6] selftest/openat2: Add tests for O

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Message-ID: <202005121452.4DED41A@keescook>
Date:   Tue, 12 May 2020 14:57:27 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     linux-kernel@...r.kernel.org, Aleksa Sarai <cyphar@...har.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Christian Heimes <christian@...hon.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Deven Bowers <deven.desai@...ux.microsoft.com>,
        Eric Chiang <ericchiang@...gle.com>,
        Florian Weimer <fweimer@...hat.com>,
        James Morris <jmorris@...ei.org>, Jan Kara <jack@...e.cz>,
        Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>,
        Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Mickaël Salaün <mickael.salaun@....gouv.fr>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Philippe Trébuchet 
        <philippe.trebuchet@....gouv.fr>,
        Scott Shell <scottsh@...rosoft.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Shuah Khan <shuah@...nel.org>,
        Steve Dower <steve.dower@...hon.org>,
        Steve Grubb <sgrubb@...hat.com>,
        Thibaut Sautereau <thibaut.sautereau@....gouv.fr>,
        Vincent Strubel <vincent.strubel@....gouv.fr>,
        kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v5 4/6] selftest/openat2: Add tests for O_MAYEXEC
 enforcing

On Tue, May 05, 2020 at 05:31:54PM +0200, Mickaël Salaün wrote:
> Test propagation of noexec mount points or file executability through
> files open with or without O_MAYEXEC, thanks to the
> fs.open_mayexec_enforce sysctl.
> 
> Signed-off-by: Mickaël Salaün <mic@...ikod.net>
> Reviewed-by: Thibaut Sautereau <thibaut.sautereau@....gouv.fr>
> Cc: Aleksa Sarai <cyphar@...har.com>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Shuah Khan <shuah@...nel.org>

Yay tests! :) Notes below...

> diff --git a/tools/testing/selftests/openat2/Makefile b/tools/testing/selftests/openat2/Makefile
> index 4b93b1417b86..cb98bdb4d5b1 100644
> --- a/tools/testing/selftests/openat2/Makefile
> +++ b/tools/testing/selftests/openat2/Makefile
> @@ -1,7 +1,8 @@
>  # SPDX-License-Identifier: GPL-2.0-or-later
>  
>  CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined
> -TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test
> +LDLIBS += -lcap
> +TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test omayexec_test

I realize the others have _test in their name, but that feels intensely
redundant to me. :)

> [...]
> diff --git a/tools/testing/selftests/openat2/omayexec_test.c b/tools/testing/selftests/openat2/omayexec_test.c
> new file mode 100644
> index 000000000000..7052c852daf8
> --- /dev/null
> +++ b/tools/testing/selftests/openat2/omayexec_test.c
> [...]
> +FIXTURE_DATA(mount_exec_file_exec) { };

For each of these, Please use "FIXTURE" not "FIXTURE_DATA". See:
1ae81d78a8b2 ("selftests/seccomp: Adjust test fixture counts")

> +FIXTURE_SETUP(mount_exec_file_exec)
> +{
> +	create_workspace(_metadata, 1, 1);

Maybe save the system's original sysctl in create_workspace() instead
of always restoring it to 0 in delete_workspace()?

Otherwise, looks good!

-- 
Kees Cook