drm/vmwgfx: avoid destroy_workqueue(NULL) on vkms init failure

Overview

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.

Affected

• Linux >= 7b0062036c3b71b4a69e244ecf0502c06c4cf5f0 < 7c701778c6a369769992614dac8dc00c8ac72afc
• Linux >= 7b0062036c3b71b4a69e244ecf0502c06c4cf5f0 < 96efee36453b697ccbaf75091b7a1807c11809dd
• Linux >= 7b0062036c3b71b4a69e244ecf0502c06c4cf5f0 < 0ee0532f1d405d37f38c44cbba87342e63d3bbd4
• Linux >= 7b0062036c3b71b4a69e244ecf0502c06c4cf5f0 < 05eaa887e7b4f40fba425f8a1d7a5a8a043092a6
• Linux 6.10

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.