Linux Kernel BCM2835 Power Domain ASB Control Timeout Vulnerability

A vulnerability in the Linux kernel's handling of power domains for the BCM2835 chip can lead to issues with the ASB (AXI Stream Bus) control for the V3D graphics processor. During heavy workloads, the ASB bridge may not acknowledge requests in a timely manner, causing errors that leave the V3D processor in a malfunctioning state. This can result in bus faults or system hangs during later operations. The issue arises because the polling loop used to wait for ASB acknowledgments has an inadequate timeout, which has now been increased from 1 microsecond to 5 microseconds. The vulnerability affects the Linux kernel stable tree, specifically in the drivers for the BCM2835 power management.

Impact

The vulnerability can cause the V3D graphics processor to enter a faulty state, leading to bus faults or system freezes during subsequent operations.

Reproduction

The vulnerability can be reproduced by placing the V3D graphics processor under heavy workload, which can be done through graphics-intensive applications or benchmarks. During this time, the ASB control function will fail to properly acknowledge requests, causing the power management system to leave the V3D processor in a broken state.

Remediation

The vulnerability has been addressed in the Linux kernel by increasing the ASB control timeout and modifying the polling mechanism to be more reliable. Users can upgrade to the latest version of the Linux kernel stable tree to apply this fix.