Security: Introduce security= boot parameter

Add the security= boot parameter. This is done to avoid LSM
registration clashes in case of more than one bult-in module.

User can choose a security module to enable at boot. If no
security= boot parameter is specified, only the first LSM
asking for registration will be loaded. An invalid security
module name will be treated as if no module has been chosen.

LSM modules must check now if they are allowed to register
by calling security_module_enable(ops) first. Modify SELinux
and SMACK to do so.

Do not let SMACK register smackfs if it was not chosen on
boot. Smackfs assumes that smack hooks are registered and
the initial task security setup (swapper->security) is done.

Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
Acked-by: James Morris <jmorris@namei.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index a2f7e9c..f9927f02 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5295,6 +5295,8 @@ static int selinux_key_permission(key_ref_t key_ref,
 #endif
 
 static struct security_operations selinux_ops = {
+	.name =				"selinux",
+
 	.ptrace =			selinux_ptrace,
 	.capget =			selinux_capget,
 	.capset_check =			selinux_capset_check,
@@ -5492,6 +5494,11 @@ static __init int selinux_init(void)
 {
 	struct task_security_struct *tsec;
 
+	if (!security_module_enable(&selinux_ops)) {
+		selinux_enabled = 0;
+		return 0;
+	}
+
 	if (!selinux_enabled) {
 		printk(KERN_INFO "SELinux:  Disabled at boot.\n");
 		return 0;