Fast Intra-Kernel Isolation and Security with Iskios Spyridoula Gravani John Criswell Mohammad Hedayati Michael L
Fast Intra-kernel Isolation and Security with IskiOS Spyridoula Gravani John Criswell Mohammad Hedayati Michael L. Scott {sgravani,hedayati}@cs.rochester.edu {criswell,scott}@cs.rochester.edu University of Rochester University of Rochester ABSTRACT jeopardize the security of the entire system. To safeguard system The kernels of operating systems such as Windows, Linux, and integrity, control-flow integrity (CFI) enforcement [22, 31, 56, 66] MacOS are vulnerable to control-flow hijacking. Defenses exist, but ensures that only paths in an authorized control-flow graph are many require efficient intra-address-space isolation. Execute-only followed during execution [1]. At the same time, leakage-resilient memory, for example, requires read protection on code segments, diversification [4, 6, 21, 32, 33, 71] undermines the attacker’s knowl- and shadow stacks require protection from buffer overwrites. Intel’s edge of the code layout in memory, making successful exploitation Protection Keys for Userspace (PKU) could, in principle, provide more difficult. Both techniques must efficiently isolate memory the intra-kernel isolation needed by such defenses, but, when used within the OS kernel. CFI must protect the integrity of return ad- as designed, it applies only to user-mode application code. dresses on the stack [8, 10, 10, 17, 30, 34]; diversification must This paper presents an unconventional approach to memory pro- prevent attackers from learning the layout of kernel code—e.g., by tection, allowing PKU to be used within the operating system kernel leveraging buffer overreads [78, 79]. on existing Intel hardware, replacing the traditional user/supervisor Existing intra-kernel isolation mechanisms generally rely on isolation mechanism and, simultaneously, enabling efficient intra- software fault isolation (SFI) [76, 86], adding bounds checks to mem- kernel isolation.
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