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As control-flow protection techniques are widely deployed, it is difficult for attackers to modify control data, like function pointers, to hijack program control flow. Instead, data-only attacks corrupt security-critical non-control data (critical data), and can bypass all control-flow protections to revive severe attacks. Previous works have explored various methods to help construct or prevent data-only attacks. However, no solution can automatically detect program-specific critical data. In this paper, we identify an important category of critical data, syscall-guard variables, and propose a set of solutions to automatically detect such variables in a scalable manner. Syscall-guard variables determine to invoke security-related system calls (syscalls), and altering them will allow attackers to request extra privileges from the operating system. We propose branch force, which intentionally flips every conditional branch during the execution and checks whether new security-related syscalls are invoked. If so, we conduct data-flow analysis to estimate the feasibility to flip such branches through common memory errors. We build a tool, VIPER, to implement our ideas. VIPER successfully detects 34 previously unknown syscall-guard variables from 13 programs. We build four new data-only attacks on sqlite and v8, which execute arbitrary command or delete arbitrary file. VIPER completes its analysis within five minutes for most programs, showing its practicality for spotting syscall-guard variables. 

Go is a young programming language invented to build safe and efficient concurrent programs. It provides goroutines as lightweight threads and channels for inter-goroutine communication. Programmers are encouraged to explicitly pass messages through channels to connect goroutines, with the purpose of reducing the chance of making programming mistakes and introducing concurrency bugs. Go is one of the most beloved programming languages and has already been used to build many critical infrastructure software systems in the data-center environment. However, a recent study shows that channel-related concurrency bugs are still common in Go programs, severely hurting the reliability of the programs. This paper presents GFuzz, a dynamic detector that can effectively pinpoint channel-related concurrency bugs by mutating the processing orders of concurrent messages. We build GFuzz in three steps. We first adopt an effective approach to identify concurrent messages and transform a program to process those messages in any given order. We then take a fuzzing approach to generate new processing orders by mutating exercised ones and rely on execution feedback to prioritize orders close to triggering bugs. Finally, we design a runtime sanitizer to capture triggered bugs that are missed by the Go runtime. We evaluate GFuzz on seven popular Go software systems, including Docker, Kubernetes, and gRPC. GFuzz finds 184 previously unknown bugs and reports a negligible number of false positives. Programmers have already confirmed 124 reports as real bugs and fixed 67 of them based on our reporting. A careful inspection of the detected concurrency bugs from gRPC shows the effectiveness of each component of GFuzz and confirms the components' rationality.