CVE-2015-6995

El componente Disk Images en Apple iOS en versiones anteriores a 9.1 y OS X en versiones anteriores a 10.11.1 no analiza correctamente imágenes, lo que permite a atacantes ejecutar código arbitrario o provocar una denegación de servicio (corrupción de memoria) a través de una aplicación manipulada.

Method 5 of the IOHDIXController user client is createDrive64. This takes a 0x10 0 byte structure input from which it reads a userspace pointer and a size which it passes to IOHDIXController::convertClientBuffer. This wraps the memory pointed to by the userspace pointer in an IOMemoryDescriptor then takes the user-provided size, casts it to a 32-bit type and adds one. It passes that value to IOMalloc. By passing a size of 0xffffffff we can cause an integer overflow and IOMalloc will be passed a size of 0. IOMalloc falls through to kalloc which will quite happily make a 0-sized allocation for us and return a valid, writable kernel heap pointer.