CVE-2021-47330

What it actually does

Memory leak occurs in the serial_cs probe function when serial_config() fails after allocation of the 'info' structure, leaving the memory unfreed in the error path.

Why it matters to the business

Repeated probe failures on systems using PCMCIA serial cards can gradually exhaust kernel memory, leading to degraded performance or instability over extended operation; the issue has been public for over two years with negligible exploit activity and no mandated remediation deadlines.

How an attack unfolds

An attacker would need local access or the ability to trigger repeated device probe failures in the 8250 serial_cs driver; the flaw is not known to be used by any threat actors and carries no observed exploitation path beyond resource exhaustion in controlled error scenarios.

How to fix it

Apply the upstream kernel commit that adds proper resource cleanup in the probe error path; upgrade to a kernel version containing the fix for CVE-2021-47330.

How to confirm the fix worked

Inspect kernel source for the added error-handling free of the 'info' structure in serial_cs.c or verify the running kernel includes the 2021-era serial_cs probe fix.

Typical attack path

1. Obtain ability to trigger serial_cs device attachment or probe operations
2. Force serial_config() to fail after 'info' allocation
3. Repeat to accumulate leaked kernel memory

How to detect it

Search kernel logs and dmesg for repeated serial_cs probe error paths; no public indicators of active exploitation exist.

What your security team should do

• Prioritize kernel updates on systems using legacy PCMCIA serial hardware
• Monitor memory usage patterns during device probe events
• Review logs for repeated serial_cs probe failures