Static Analysis of Context Leaks in Android Applications

Abstract

Android native applications, written in Java and distributed in APK format, are widely used in mobile devices. Their specific pattern of use lets the operating system control the creation and destruction of key resources, such as activities and services (contexts). Programmers are not supposed to interfere with such lifecycle events. Otherwise contexts might be leaked, i.e. they will never be deallocated from memory, or be deallocated too late, leading to memory exhaustion and frozen applications. In practice, it is easy to write incorrect code, which hinders garbage collection of contexts and subsequently leads to context leakage. In this work, we present a new static analysis method that finds context leaks in Android code. We apply this analysis to APKs translated into Java bytecode. We discuss the results of a large number of experiments with our analysis, which reveal context leaks in many widely used applications from the Android marketplace. This shows the practical usefulness of our technique and proves its superiority w.r.t. the well-known Lint static analysis tool. We then estimate the amount of memory saved by the collection of the leaks found and explain, experimentally, where programmers often go wrong and what the analysis is not yet able to find. Such lessons could be later leveraged for the definition of a sound or more powerful static analysis for Android leaks. This work can be considered as a practical application of software analysis techniques to solve practical problems.