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:
- 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.
- 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.