Linux Kernel Alpha Memory Compaction TLB Invalidation Vulnerability

A vulnerability in the Linux kernel on Alpha systems can lead to user-space crashes and heap corruption when memory compaction is enabled. This issue arises from insufficient translation lookaside buffer (TLB) shootdown during page migration, causing stale data or instruction translations to persist, which can disrupt memory management and cache coherency. The problem manifests as segmentation faults, glibc allocator errors, and internal compiler errors, but disappears when compaction is turned off or when global TLB invalidation is applied. The vulnerability affects several versions of the Linux kernel.

Impact

The vulnerability can cause sporadic user-space crashes and heap corruption, with symptoms including segmentation faults, glibc allocator failures, and internal compiler errors.

Reproduction

The vulnerability can be reproduced on an Alpha system by enabling memory compaction, which will lead to the observed user-space crashes and heap corruption. Disabling compaction or using global TLB invalidation will mitigate the issue.

Remediation

The vulnerability has been addressed in the Linux kernel by introducing a migration-specific helper that combines MM context invalidation, immediate per-CPU TLB invalidation, and synchronous cross-CPU shootdown when required. This update is available in the latest Linux kernel releases.