Vulnerability Advisory : ACPI: PRM: Find EFI_MEMORY_RUNTIME block for PRM handler and context with LOW Attack Complexity

In the Linux kernel, the following vulnerability has been resolved: ACPI: PRM: Find EFI_MEMORY_RUNTIME block for PRM handler and context PRMT needs to find the correct type of block to translate the PA-VA mapping for EFI runtime services. The issue arises because the PRMT is finding a block of type EFI_CONVENTIONAL_MEMORY, which is not appropriate for runtime services as described in Section 2.2.2 (Runtime Services) of the UEFI Specification [1]. Since the PRM handler is a type of runtime service, this causes an exception when the PRM handler is called. [Firmware Bug]: Unable to handle paging request in EFI runtime service WARNING: CPU: 22 PID: 4330 at drivers/firmware/efi/runtime-wrappers.c:341 __efi_queue_work+0x11c/0x170 Call trace: Let PRMT find a block with EFI_MEMORY_RUNTIME for PRM handler and PRM context. If no suitable block is found, a warning message will be printed, but the procedure continues to manage the next PRM handler. However, if the PRM handler is actually called without proper allocation, it would result in a failure during error handling. By using the correct memory types for runtime services, ensure that the PRM handler and the context are properly mapped in the virtual address space during runtime, preventing the paging request error. The issue is really that only memory that has been remapped for runtime by the firmware can be used by the PRM handler, and so the region needs to have the EFI_MEMORY_RUNTIME attribute. [ rjw: Subject and changelog edits ]