selinux: clean up avc node cache when disabling selinux

Added a call to free the avc_node_cache when inside selinux_disable because
it should not waste resources allocated during avc_init if SELinux is disabled
and the cache will never be used.

Signed-off-by: Thomas Liu <tliu@redhat.com>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

security/selinux/avc.c

@@ -970,3 +970,9 @@ u32 avc_policy_seqno(void)
 {
 	return avc_cache.latest_notif;
 }
+
+void avc_disable(void)
+{
+	if (avc_node_cachep)
+		kmem_cache_destroy(avc_node_cachep);
+}

security/selinux/hooks.c

@@ -5683,6 +5683,9 @@ int selinux_disable(void)
 	selinux_disabled = 1;
 	selinux_enabled = 0;
 
+	/* Try to destroy the avc node cache */
+	avc_disable();
+
 	/* Reset security_ops to the secondary module, dummy or capability. */
 	security_ops = secondary_ops;
 

security/selinux/include/avc.h

@@ -131,6 +131,9 @@ int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
 int avc_get_hash_stats(char *page);
 extern unsigned int avc_cache_threshold;
 
+/* Attempt to free avc node cache */
+void avc_disable(void);
+
 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
 DECLARE_PER_CPU(struct avc_cache_stats, avc_cache_stats);
 #endif