The Linux kernel's push for higher I/O performance and more efficient memory management has introduced new mechanisms that, while improving performance, also open new attack surfaces. This research examines two of them together: the io_uring subsystem and the sheaf/barn caching mechanism added to the SLUB allocator in Linux 6.18. In this research, two previously unknown vulnerabilities in io_uring are presented, and one is developed into a complete local privilege escalation chain under a hardened kernel configuration. Building this chain revealed that the sheaf/barn mechanism changes long-standing assumptions behind established exploitation techniques such as cross-cache attack, and that its design also weakens existing SLUB freelist protections. Both observations are analyzed and turned into working primitives. Building on this analysis, three novel sheaf-based exploitation techniques are proposed. Among them, an RCU-sheaf cross-cache technique removes the traditional dependence on the buddy system for moving objects across caches, giving more flexible and reliable control over object migration between cache pools. Together, these results characterize the sheaf/barn layer as a new and largely unexplored attack surface in Linux kernel exploitation.

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