CVE-2023-52485

What it actually does

Failure to wake the DMCUB before issuing display micro-controller commands can cause the kernel to hang indefinitely while waiting for command submission in the AMD display driver due to missing enter/exit idle power sequencing around dm_execute_dmub_cmd calls.

Why it matters to the business

Systems using AMD graphics hardware may experience unexpected freezes or hangs during graphics operations, leading to loss of productivity, service disruption, and potential data loss on unrecovered systems; the issue affects a wide range of Linux kernel deployments with high ecosystem prevalence.

How an attack unfolds

An attacker with local access triggers idle power optimizations on the DMCUB then performs display command submissions that bypass the required wake sequencing, resulting in a hang within DC context or DM direct submission paths.

How to fix it

Update the Linux kernel to include commit 303197775a97416b62d4da69280d0c120a20e009 or later; for DM direct submissions, implement manual enter/exit idle sequencing around command submission.

How to confirm the fix worked

Confirm the presence of wake-before-command logic wrapping dm_execute_dmub_cmd/list calls in the AMD display driver source, then exercise display operations after power state transitions to verify absence of hangs.

Typical attack path

1. Obtain local code execution or shell access on a Linux system with AMD display hardware
2. Force DMCUB into idle power state
3. Invoke graphics or display operations that submit commands without proper wake handling
4. Trigger indefinite hang in the driver

How to detect it

Review kernel logs for entries related to DMCUB command submission failures or display driver hangs, and correlate with system unresponsiveness during graphics activity on AMD hardware.

What your security team should do

• Prioritize kernel updates containing the referenced commit on all AMD-based Linux systems
• Apply updates before the next scheduled maintenance window given the 960-day exposure window
• Temporarily restrict untrusted local user access to graphics subsystems until patched