wrong of info-flow-shm, it is a inductive(transitive) notion, not a simple relation just between 2 nodes, more information, see 5.7 of ideas_of_selinux.txt
info_flow_shm is wrongly defined: p -flow-> p'; p' -flow-> p'' ==> p -flow-> p'', this property cannot be infered by current definition. we should use inductive