Hardening OS kernels against memory errors is generally addressed by protecting security-critical data against corruption and disclosure. However, establishing a sound model for identifying sensitive memory objects in need of protection is hard, leading to emergent attack vectors that can be abused by attackers. In this paper, we propose rethinking how OS kernels are hardened by introducing IUBIK for compartmentalizing kernel memory. IUBIK prevents kernel exploitation by segregating attacker-controlled data-frequently used to manipulate security-critical data-in shadow memory, preventing it from interacting with sensitive kernel objects. To achieve this, IUBIK uses MTE: a recent hardware feature, available in ARM CPUs, which allows mitigating exploits based on both spatial and temporal memory-errors, efficiently. We ensure that segregated objects do not contain sensitive fields, such as pointers, by rewriting their struct definitions. Moreover, we develop a profiling framework that explores the kernel codebase in-depth and records code sites where attacker-controlled objects are allocated, allowing IUBIK to isolate them; our profiler recorded 292 privileged and 212 non-privileged allocation sites for a diverse set of workloads. Finally, we evaluate an implementation of IUBIK for the Linux kernel, across a suite of micro- and macro-benchmarks, demonstrating that our prototype incurs no runtime overhead in most tests and negligible additional memory consumption.

Historically, researchers have treated memory safety-based and speculative execution attacks as two separate domains. Recent work has introduced Speculative Memory-error Abuse (SMA) attacks, which combine memory corruption vulnerabilities with Spectre-like primitives. Using SMA, an attacker can leak sensitive program information and defeat a wide variety of memory-corruption mitigations, including (K)ASLR, software-based XOM, and even ARM PA, eventually carrying out an end-to-end (architecturally-visible) exploit. We present Eclipse: a novel protection scheme against SMA attacks. Eclipse works by propagating artificial data dependencies onto sensitive data, preventing the CPU from using attacker-controlled data during speculative execution. We demonstrate that Eclipse provides comprehensive protection against speculative-probing and Pacman-style attacks, two prominent examples of Speculative Memory-error Abuse attacks that target both the x86(-64) and ARM architectures. We evaluate the performance of Eclipse on x86-64 and demonstrate that it introduces minimal overhead, compared to alternative hardening approaches, incurring ≈0%--9.5% slowdown on SPEC CPU 2017, up to 8.6% slowdown in real-world applications, and negligible overhead in the Linux kernel.

We present the design, implementation, and evaluation of SysXCHG: a system call (syscall) filtering enforcement mechanism that enables programs to run in accordance with the principle of least privilege. In contrast to the current, hierarchical design of seccomp-BPF, which does not allow a program to run with a different set of allowed syscalls than its descendants, SysXCHG enables applications to run with "tight" syscall filters, uninfluenced by any future-executed (sub-)programs, by allowing filters to be dynamically exchanged at runtime during execve[at]. As a part of SysXCHG, we also present xfilter: a mechanism for fast filtering using a process-specific view of the kernel's syscall table where filtering is performed. In our evaluation of SysXCHG, we found that our filter exchanging design is performant, incurring ≤= 1.71% slowdown on real-world programs in the PaSH benchmark suite, as well as effective, blocking vast amounts of extraneous functionality, including security-critical syscalls, which the current design of seccomp-BPF is unable to.

We present the design, implementation, and evaluation of FineIBT: a CFI enforcement mechanism that improves the precision of hardware-assisted CFI solutions, like Intel IBT, by instrumenting program code to reduce the valid/allowed targets of indirect forward-edge transfers. We study the design of FineIBT on the x86-64 architecture, and implement and evaluate it on Linux and the LLVM toolchain. We designed FineIBT’s instrumentation to be compact, incurring low runtime and memory overheads, and generic, so as to support different CFI policies. Our prototype implementation incurs negligible runtime slowdowns (≈ 0%–1.94% in SPEC CPU2017 and ≈ 0%–1.92% in real-world applications) outperforming Clang-CFI. Lastly, we investigate the effectiveness/security and compatibility of FineIBT using the ConFIRM CFI benchmarking suite, demonstrating that our instrumentation provides complete coverage in the presence of modern software features, while supporting a wide range of CFI policies with the same, predictable performance.