CVE-2021-47057

What it actually does

Memory leak of an allocated object in the sun8i-ss crypto driver error path when dma_iv DMA mapping fails, leaving the object unfreed on that return.

Why it matters to the business

On systems using the affected Allwinner hardware crypto accelerator, repeated triggering of the error condition can slowly exhaust kernel memory, degrading performance or causing instability over time; low EPSS and absence from KEV indicate limited real-world urgency.

How an attack unfolds

An attacker with local access or the ability to induce DMA mapping failures in the sun8i-ss driver repeatedly triggers the buggy error path, leaking kernel memory each time until the system becomes unstable or crashes.

How to fix it

Update the Linux kernel to a version containing the upstream fix for the sun8i-ss memory leak; rebuild and deploy the updated kernel on affected Allwinner-based systems.

How to confirm the fix worked

Confirm the presence of the error-label fix in the sun8i-ss driver source; monitor kernel memory usage statistics under load that previously triggered the leak path.

Typical attack path

1. Obtain local execution or control over crypto operations that reach the sun8i-ss driver.
2. Force conditions where dma_iv mapping fails (e.g., resource exhaustion or malformed requests).
3. Repeat the operation to accumulate leaked kernel memory objects.
4. Monitor for gradual memory pressure leading to denial of service.

How to detect it

Examine kernel logs for repeated sun8i-ss DMA mapping failures; correlate with gradual increases in kernel memory usage or slab allocator statistics on affected hardware.

What your security team should do

• Prioritize kernel updates on any systems exposing the sun8i-ss driver.
• Review crypto hardware usage and consider software fallback if updates cannot be applied promptly.
• Monitor memory consumption metrics on affected devices for unexpected growth.