[PATCH v5 4/6] selftest/openat2: Add tests for O_MAYEXEC enforcing

[Kees Cook]

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 at digikod.net>
> Reviewed-by: Thibaut Sautereau <thibaut.sautereau at ssi.gouv.fr>
> Cc: Aleksa Sarai <cyphar at cyphar.com>
> Cc: Al Viro <viro at zeniv.linux.org.uk>
> Cc: Kees Cook <keescook at chromium.org>
> Cc: Shuah Khan <shuah at kernel.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