Kernel extension verification is untenable.

Jinghao Jia,Raj Sahu, Adam Oswald,Dan Williams, Michael V. Le,Tianyin Xu


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The emergence of verified eBPF bytecode is ushering in a new era of safe kernel extensions. In this paper, we argue that eBPF's verifier---the source of its safety guarantees---has become a liability. In addition to the well-known bugs and vulnerabilities stemming from the complexity and ad hoc nature of the in-kernel verifier, we highlight a concerning trend in which escape hatches to unsafe kernel functions (in the form of helper functions ) are being introduced to bypass verifier-imposed limitations on expressiveness, unfortunately also bypassing its safety guarantees. We propose safe kernel extension frameworks using a balance of not just static but also lightweight runtime techniques. We describe a design centered around kernel extensions in safe Rust that will eliminate the need of the in-kernel verifier, improve expressiveness, allow for reduced escape hatches, and ultimately improve the safety of kernel extensions.
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