Liang Zhang

**Name of the Vulnerable Software and Affected Versions** Linux kernel version 5.10.0 **Description** The vulnerability is related to the KVM (Kernel-based Virtual Machine) component of the Linux kernel, specifically in the x86/mmu (Memory Management Unit) module. The issue arises from the async pagefault logic, where the KVM relies on the `kvm arch can dequeue async page present()` function to determine whether to deliver a READY event to the Guest. This function checks the token value of the `struct kvm vcpu pv apf data`, which must be reset to zero by the Guest kernel when a READY event is finished. However, the `kvm arch setup async pf()` function may produce a valid token with a zero value, leading to confusion and potentially causing the loss of the READY event. This bug can cause tasks to be blocked forever in the Guest, as indicated by the error message "INFO: task stress:7532 blocked for more than 1254 seconds." **Recommendations** To resolve this issue, update the Linux kernel to a version that includes the fix for this vulnerability. Specifically, ensure that the KVM component is updated to use a non-zero token value to avoid confusion with previous mentions. As a temporary workaround, consider disabling the `kvm arch setup async pf()` function until a patch is available. Additionally, restrict access to the vulnerable module to minimize the risk of exploitation.