core: reload SELinux label cache on daemon-reload

Reloading the SELinux label cache here enables a light-wight follow-up of a SELinux policy change, e.g. adding a label for a RuntimeDirectory.

Closes: #13363

src/basic/selinux-util.c

@@ -107,6 +107,26 @@ void mac_selinux_finish(void) {
 #endif
 }
 
+void mac_selinux_reload(void) {
+
+#if HAVE_SELINUX
+        struct selabel_handle *backup_label_hnd;
+
+        if (!label_hnd)
+                return;
+
+        backup_label_hnd = TAKE_PTR(label_hnd);
+
+        /* try to initialize new handle
+         *    on success close backup
+         *    on failure restore backup */
+        if (mac_selinux_init() == 0)
+                selabel_close(backup_label_hnd);
+        else
+                label_hnd = backup_label_hnd;
+#endif
+}
+
 int mac_selinux_fix(const char *path, LabelFixFlags flags) {
 
 #if HAVE_SELINUX

src/basic/selinux-util.h

@@ -13,6 +13,7 @@ void mac_selinux_retest(void);
 
 int mac_selinux_init(void);
 void mac_selinux_finish(void);
+void mac_selinux_reload(void);
 
 int mac_selinux_fix(const char *path, LabelFixFlags flags);
 int mac_selinux_apply(const char *path, const char *label);