CHERI-D targets the gap in CHERI's architecture that forces software workarounds for temporal memory safety, specifically the overhead of revocation that limits Cornucopia Reloaded to weaker use-after-reallocation (UAR) protections instead of full use-after-free (UAF) mitigation.
Why CHERI's Temporal Safety Gap Matters
CHERI gives hardware-enforced spatial safety through capabilities, but temporal safety - preventing use-after-free exploits - remains a software patch. Cornucopia Reloaded, the state-of-the-art, delays reallocation and uses revocation to catch dangling pointers. That approach costs performance and only blocks reuse of the same allocation, not reuse of the freed memory itself. CHERI-D closes that gap by adding architectural support for object IDs directly tied to capabilities.
How CHERI-D Packs Object IDs Into Capability Slack
CHERI-D associates an object identification (ID) metadata with each capability pointer. Because CHERI already enforces spatial safety, the object ID can be stored inline with the allocation data - specifically in unused fragmentation within the capability's bounds. No separate protection mechanism needed. The capability itself becomes the carrier of temporal integrity, tying every access to the original allocation's identity.
Simulation and Hardware Results Show Real Gains
The paper evaluates CHERI-D in simulation and actual hardware. Compared to Cornucopia Reloaded, CHERI-D significantly reduces revocation overhead while upgrading from use-after-reallocation to strict use-after-free protection. Exact numbers are paper-only, but the architectural change eliminates the delayed-reallocation overhead that made Cornucopia choose the weaker guarantee.
CHERI-D makes temporal memory safety a first-class hardware feature, not a software tax. Expect this design to influence future capability-based architectures aiming for full memory safety without the performance penalty of software revocation sweeps.
Source: CHERI-D: Secure and efficient inline object ID for CHERI temporal memory safety
Domain: arxiv.org
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