Linux Kernel ACR Mask Validation and Configuration Vulnerability

A vulnerability in the Linux kernel's handling of ACR (Architectural Performance Monitoring) masks has been addressed. The issue stemmed from incomplete validation of user space ACR masks, which could inadvertently include indices from other ACR event groups. Additionally, an early return on encountering an invalid ACR mask caused subsequent ACR groups to be skipped, and the stale hardware ACR mask was not cleared before applying a new one. The vulnerability affected the Linux kernel stable tree.

Impact

The vulnerability could lead to improper configuration of ACR event masks, potentially causing performance monitoring errors. Incomplete validation allowed for cross-contamination of event group indices, and failure to clear stale hardware masks could disrupt accurate event tracking.

Reproduction

The vulnerability can be reproduced by configuring ACR event masks in user space without proper validation. This can be done by including indices from different ACR event groups, which the current validation process does not adequately check. The resulting misconfiguration can be observed by monitoring the performance events, where the errors caused by the invalid mask will be reflected.

Remediation

Users can upgrade to the latest version of the Linux kernel, where this vulnerability has been fixed. Instructions for downloading the updated kernel can be found on the Linux kernel official website.