CVE-2020-36310: 
Linux Kernel vulnerability analysis and mitigation

A flaw was discovered in the Linux kernel before version 5.8, specifically in the KVM (Kernel Virtual Machine) implementation for AMD processors in the file arch/x86/kvm/svm/svm.c. The vulnerability allows a setmemoryregion_test infinite loop for certain nested page faults, identified as CVE-2020-36310. This vulnerability was later addressed in kernel version 5.8 through commit e72436bc3a52 (Kernel Commit).

The vulnerability occurs when a nested page fault is taken from an address that does not have a memslot associated with it. In such cases, kvmmmudopagefault returns RETPFEMULATE through mmusetspte, and kvmmmupagefault then invokes svmneedemulationonpagefault. The default behavior of returning false causes the page fault to be retried indefinitely, resulting in an infinite loop (Kernel Commit).

When exploited, this vulnerability could allow a malicious virtual machine guest to cause a denial of service condition in the host system by triggering an infinite loop in the KVM subsystem (Debian Security).

The vulnerability was fixed in Linux kernel version 5.8 by adding a kvmvcpugfntomemslot check in svmneedemulationonpage_fault to detect cases where the erratum is not occurring. Various distributions have backported this fix, including Debian which addressed it in version 5.10.103-1 (Debian Security).