Security: add static to security_ops and default_security_ops variable

Enhance the security framework to support resetting the active security
module. This eliminates the need for direct use of the security_ops and
default_security_ops variables outside of security.c, so make security_ops
and default_security_ops static. Also remove the secondary_ops variable as
a cleanup since there is no use for that. secondary_ops was originally used by
SELinux to call the "secondary" security module (capability or dummy),
but that was replaced by direct calls to capability and the only
remaining use is to save and restore the original security ops pointer
value if SELinux is disabled by early userspace based on /etc/selinux/config.
Further, if we support this directly in the security framework, then we can
just use &default_security_ops for this purpose since that is now available.

Signed-off-by: Zhitong Wang <zhitong.wangzt@alibaba-inc.com>
Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 9 insertions, 2 deletions

diff --git a/security/security.c b/security/security.c
index 971092c06f31..edae56b78771 100644
--- a/security/security.c
+++ b/security/security.c
@@ -23,10 +23,12 @@ static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
         CONFIG_DEFAULT_SECURITY;
 
 /* things that live in capability.c */
-extern struct security_operations default_security_ops;
 extern void security_fixup_ops(struct security_operations *ops);
 
-struct security_operations *security_ops;       /* Initialized to NULL */
+static struct security_operations *security_ops;
+static struct security_operations default_security_ops = {
+        .name   = "default",
+};
 
 static inline int verify(struct security_operations *ops)
 {
@@ -63,6 +65,11 @@ int __init security_init(void)
         return 0;
 }
 
+void reset_security_ops(void)
+{
+        security_ops = &default_security_ops;
+}
+
 /* Save user chosen LSM */
 static int __init choose_lsm(char *str)
 {