Medium [CVE-2026-74442] avoid destroy_workqueue(NULL) on vkms init failure

In the Linux kernel, the following vulnerability has been resolved: drm/vmwgfx: avoid destroy_workqueue(NULL) on vkms init failure Two paths through vmw_vkms_init() can leave vmw->crc_workq NULL while still leaving the rest of the driver in a state that calls vmw_vkms_cleanup() at module unload: 1. vmw_host_get_guestinfo(GUESTINFO_VBLANK,...) failing or returning an oversized buffer -- the common case on hosts without a VBLANK guestinfo entry -- early-returned before the workqueue allocation.

2. alloc_ordered_workqueue() returning NULL on memory pressure. vmw_vkms_cleanup() then calls destroy_workqueue(NULL), which dereferences wq->name and panics.

Fix the first case by removing the early return: vmw->vkms_enabled is already false on the rpci-failure path so no work will ever be queued, and allocating the workqueue unconditionally keeps the control flow simple. Fix the second case by guarding the cleanup with a NULL check, since alloc_ordered_workqueue() can still fail under low memory.

This vulnerability occurs when the `vmw_vkms_init()` function fails to initialize a workqueue, leaving a pointer as NULL. During module unload, the `vmw_vkms_cleanup()` function attempts to destroy this NULL workqueue, leading to a kernel panic.

A local attacker could potentially trigger this condition, resulting in a system crash and a Denial of Service (DoS).