The Linux kernel contained a vulnerability where ACPI PRM calls, delegated to a workqueue running in a kernel thread, could trigger NULL pointer dereferences if such calls occurred before the runtime workqueue was allocated in efisubsys_init(). Because acpi_init() runs as a subsys_initcall() and cannot be deferred, the solution was to allocate the runtime workqueue earlier in the boot process as a postcore initcall. This change ensures EFI runtime calls, including PRM handlers, are available to all code running at the subsys_initcall() level, preventing potential faults caused by premature PRM accesses.

The vulnerability could cause NULL pointer dereferences in the kernel due to premature ACPI PRM calls before the runtime workqueue allocation. This may lead to kernel faults or crashes. No known exploits in the wild have been reported. The impact is limited to kernel stability and reliability during early initialization phases involving EFI runtime calls.

A fix has been implemented in the Linux kernel by allocating the EFI runtime workqueue earlier during the boot process (postcore initcall). Users should update to a Linux kernel version that includes commit 5894cf571e14 or later to remediate this issue. Patch status is confirmed by the vendor commit; no additional mitigation is required.