security: allow Yama to be unconditionally stacked

Unconditionally call Yama when CONFIG_SECURITY_YAMA_STACKED is selected,
no matter what LSM module is primary.

Ubuntu and Chrome OS already carry patches to do this, and Fedora
has voiced interest in doing this as well. Instead of having multiple
distributions (or LSM authors) carrying these patches, just allow Yama
to be called unconditionally when selected by the new CONFIG.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: Eric Paris <eparis@redhat.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/security/yama/Kconfig b/security/yama/Kconfig
index 51d6709d8bbd..20ef5143c0c0 100644
--- a/security/yama/Kconfig
+++ b/security/yama/Kconfig
@@ -11,3 +11,11 @@ config SECURITY_YAMA
           Further information can be found in Documentation/security/Yama.txt.
 
           If you are unsure how to answer this question, answer N.
+
+config SECURITY_YAMA_STACKED
+        bool "Yama stacked with other LSMs"
+        depends on SECURITY_YAMA
+        default n
+        help
+          When Yama is built into the kernel, force it to stack with the
+          selected primary LSM.