With the latest Linux kernel, the fuzzing process will be easier not only for our team. Thanks to Denis Valeev, who discovered, prepared, and contributed the patch to kernel v.5.16.5.

The discovered bug breaks nyx-fuzz (also included in AFL++ code base) that uses VMware backdoor as an alternative way for hypercall from guest user-mode. With this bug, a hypercall is interpreted as a GP and leads to process termination. Bug occurs on GP triggered by VMware backdoor when eax value is unaligned. eax alignment check should not be applied to non-SVM instructions because it leads to incorrect omission of the instructions emulation. The solution is to apply alignment check only to SVM instructions.