CVE-2021-47020

What it actually does

Unconditional release of slave runtime objects without prior allocation in error path leads to unfreed memory allocations in the soundwire stream configuration handling.

Why it matters to the business

Potential gradual depletion of system memory on affected Linux systems using SoundWire audio interfaces, leading to performance degradation or system instability if left unpatched; low exploitability reduces immediate urgency despite the CVE's age.

How an attack unfolds

An attacker with local access triggers a stream configuration failure in the soundwire subsystem, causing repeated allocations without corresponding frees, resulting in memory exhaustion; no known threat actors or ransomware campaigns have leveraged this issue.

How to fix it

Apply the upstream Linux kernel patch that adds explicit freeing of slave runtime objects in the stream config error path; rebuild and deploy updated kernels to affected systems.

How to confirm the fix worked

Review kernel source or changelog for the commit addressing slave runtime free in config error path; test stream config failure scenarios under memory profiling to confirm absence of leaks.

Typical attack path

1. Obtain local access to a Linux system with SoundWire enabled
2. Trigger stream configuration error conditions in the soundwire driver
3. Induce repeated failures to accumulate unfreed slave runtime allocations
4. Monitor for gradual kernel memory exhaustion

How to detect it

Examine kernel logs for soundwire stream configuration failures and employ memory leak detection tools focused on the soundwire module; no active exploitation indicators reported given zero KEV status and stable low EPSS.

What your security team should do

• Patch Linux kernels supporting SoundWire audio as part of routine updates
• Monitor system memory usage for anomalies in audio driver paths
• Limit local unprivileged access where feasible on systems with SoundWire hardware