Dear all, This series aims to provide an entrypoint for, and fuzz KVM's x86 instruction emulator from userspace. It mirrors Xen's application of the AFL fuzzer to it's instruction emulator in the hopes of discovering vulnerabilities. Since this entrypoint also allows arbitrary execution of the emulators code from userspace, it may also be useful for testing. The current 3 patches build the emulator and 2 harnesses: simple-harness is an example of unit testing; afl-harness is a frontend for the AFL fuzzer. They are early POC and include some issues outlined under "Issues." Patches ======= - 01: Builds and links afl-harness with the required kernel objects. - 02: Introduces the minimal set of emulator operations and supporting code to emulate simple instructions. - 03: Demonstrates simple-harness as a unit test. Issues ======= 1. Currently, building requires manually running the `make_deps` script since I was unable to make the kernel objects a dependency of the tool. 2. The code will segfault if `CONFIG_STACKPROTECTOR=y` in config. 3. The code requires stderr to be buffered or it otherwise segfaults. The latter two issues seem related and all of them are likely fixable by someone more familiar with the linux than me. Concerns ======= I was able to carve the `arch/x86/kvm/emulate.c` code, but the emulator is constructed in such a way that a lot of the code which enforces expected behavior lives in the x86_emulate_ops supplied in `arch/x86/kvm/x86.c`. Testing the emulator is still valuable, but a reproducible way to use the kvm ops would be useful. Any comments/suggestions are greatly appreciated. Best, Sam Caccavale Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrer: Christian Schlaeger, Ralf Herbrich Ust-ID: DE 289 237 879 Eingetragen am Amtsgericht Charlottenburg HRB 149173 B
