Linux Kernel Page Table Synchronization Vulnerability in 4-Level Paging Systems

A vulnerability in the Linux kernel's handling of page table synchronization can lead to intermittent boot failures on systems using 4-level paging and a large amount of persistent memory. This issue arises because, in 4-level paging, the default page directory population function does not perform any action, leaving certain kernel mappings unsynchronized. As a result, missing page table entries can cause kernel crashes. The vulnerability has been addressed by defining a specific synchronization function that ensures kernel mappings are properly propagated through the page tables, preventing the boot failures and crashes that were previously experienced.

Impact

The vulnerability could cause intermittent boot failures and kernel crashes due to missing page table entries for certain kernel mappings.

Reproduction

The vulnerability can be reproduced on systems using 4-level paging with a large amount of persistent memory. During the boot process, the lack of proper synchronization for kernel mappings can lead to page faults, causing the kernel to crash. This can be observed in the kernel logs, where the 'unable to handle page fault' messages indicate that the kernel is trying to access a page that is not present, due to the missing synchronization.

Remediation

Users can upgrade to the latest version of the Linux kernel, where this vulnerability has been addressed. Instructions for downloading the patched version can be found in the Linux kernel documentation.