Make the mac_policy_rm lock recursable, which allows reentrance into

the mac framework.  It is needed when priv_check_cred(9) is called from
the mac callback, e.g. in the mac_portacl(4).

Reported by:	az
Reviewed by:	rwatson
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Approved by:	re (gjb)

sys/security/mac/mac_framework.c

@@ -292,7 +292,8 @@ mac_init(void)
 	mac_labelzone_init();
 
 #ifndef MAC_STATIC
-	rm_init_flags(&mac_policy_rm, "mac_policy_rm", RM_NOWITNESS);
+	rm_init_flags(&mac_policy_rm, "mac_policy_rm", RM_NOWITNESS |
+	    RM_RECURSE);
 	sx_init_flags(&mac_policy_sx, "mac_policy_sx", SX_NOWITNESS);
 #endif
 }