CVE-2021-47053

What it actually does

Unfreed memory allocation for 'pad' on multiple error return paths in the sun8i-ss crypto driver, causing a resource leak.

Why it matters to the business

Systems using affected Allwinner hardware may gradually exhaust kernel memory during crypto operations, leading to degraded performance or crashes under sustained load.

How an attack unfolds

A local attacker triggers repeated failure conditions in sun8i-ss crypto functions to accumulate unfreed pad allocations until memory pressure causes denial of service.

How to fix it

Apply the upstream kernel patch that frees pad on all failure paths in sun8i-ss; rebuild and deploy the fixed kernel image.

How to confirm the fix worked

Inspect the sun8i-ss source for pad allocation paired with kfree on every return path; run static analysis tools such as Coverity on the driver after patching.

Typical attack path

1. Obtain local access or execute code on an affected Linux system
2. Invoke crypto operations that exercise the sun8i-ss driver error paths
3. Repeat to accumulate leaked memory allocations
4. Induce system instability or crash from kernel memory exhaustion

How to detect it

Review kernel logs for repeated sun8i-ss errors coinciding with rising slab memory usage; correlate with processes performing crypto operations on affected hardware.

What your security team should do

• Prioritize patching kernels on devices using sun8i-ss hardware crypto
• Monitor memory usage on affected systems for unexplained growth during crypto workloads
• Apply defense-in-depth by restricting untrusted local code execution