Local information disclosure via partial VDUSE configuration copy

Information disclosure in the Linux Kernel's VDUSE backend allows local users to expose uninitialized stack data through a config read. When a userspace VDUSE device advertises features needing more configuration bytes than it supplies, vduse_vdpa_get_config copies only the available bytes without initializing the remainder. Reaching the flaw requires local low-privilege access and a mismatched VDUSE device; the known consequence is indirect disclosure through kernel logs, with no direct userspace return established.