Cling: A Memory Allocator to Mitigate Dangling Pointers

Use-after-free vulnerabilities exploiting so-called dangling pointers to deallocated objects are just as dangerous as buffer overflows: they may enable arbitrary code execution. Unfortunately, state-of-the-art defenses against use-after-free vulnerabilities require compiler support, pervasive source code modifications, or incur high performance overheads. This paper presents and evaluates Cling, a memory allocator designed to thwart these attacks at runtime. Cling utilizes more address space, a plentiful resource on modern machines, to prevent typeunsafe address space reuse among objects of different types. It infers type information about allocated objects at runtime by inspecting the call stack of memory allocation routines. Cling disrupts a large class of attacks against use-after-free vulnerabilities, notably including those hijacking the C++ virtual function dispatch mechanism, with low CPU and physical memory overhead even for allocation intensive applications.