CVE-2021-47489

What it actually does

Out-of-bounds writes in multiple amdgpu debugfs handlers due to missing length validation after an earlier partial fix.

Why it matters to the business

Local memory corruption on AMD GPU systems that could lead to crashes or privilege escalation; low immediate risk given age and limited exposure but still requires patching on affected kernels.

How an attack unfolds

An attacker with local access writes crafted values to exposed debugfs files such as those in amdgpu_dm_debugfs.c, exceeding allocated buffers and corrupting adjacent kernel memory.

How to fix it

Upgrade affected Linux kernels to versions containing the referenced fixes for amdgpu_dm_debugfs.c; restrict debugfs permissions where possible.

How to confirm the fix worked

Verify kernel source contains the bounds checks added to dp_max_bpc_write and related functions; confirm no vulnerable amdgpu debugfs write paths remain.

Typical attack path

1. Obtain local shell on target system
2. Locate amdgpu debugfs entries
3. Send oversized data to vulnerable write handlers
4. Trigger kernel memory corruption

How to detect it

Review kernel logs for amdgpu debugfs write anomalies or oops reports referencing buffer overruns; no public exploitation artifacts known.

What your security team should do

• Apply kernel updates containing the amdgpu debugfs fixes
• Limit debugfs exposure on production systems
• Monitor for new EPSS increases or exploit code