Linux Kernel KVM Uninitialized Memory Pointer Vulnerability in User Memory Abort Function

A vulnerability in the Linux kernel's KVM (Kernel-based Virtual Machine) module for arm64 architecture has been addressed. The issue arose from a commit that made the initialization of a local memory cache variable in the 'user_mem_abort()' function conditional. This change inadvertently created a scenario where the variable could be used uninitialized, potentially leading to failures in functions that require a stage-2 allocation without proper permission handling or dirty logging. The vulnerability has been fixed by ensuring that the memory cache is always initialized correctly.

Impact

The vulnerability could lead to undefined behavior in the KVM module, particularly in memory management functions that require stage-2 allocations. This could cause failures in virtual machine operations that rely on these memory management features.