vKernel: Enhancing Container Isolation via Private Code and Data

Container technology is increasingly adopted in cloud environments. However, the lack of isolation in the shared kernel becomes a significant barrier to the wide adoption of containers. The challenges lie in how to simultaneously attain high performance and isolation. On the one hand, kernel-level isolation mechanisms, such as
seccomp
,
capabilities
, and
apparmor
, achieve good performance without much overhead, but lack the support for per-container customization. On the other hand, user-level and VM-based isolation offer superior security guarantees and allow for customization, since a container is assigned a dedicated kernel, but at the cost of high overhead. We present vKernel, a kernel isolation framework. It maintains a minimal set of code and data that are either sensitive or prone to interference in a
vKernel Instance
(vKI). vKernel relies on inline hooks to intercept and redirect requests sent to the host kernel to a vKI, where container-specific security rules, functions, and data are implemented. Through case studies, we demonstrate that under vKernel user-defined data isolation and kernel customization can be supported with a reasonable engineering effort. An evaluation of vKernel with micro-benchmarks, cloud services, real-world applications show that vKernel achieves good security guarantees, but with much less overhead.