CVE-2021-47150

What it actually does

Failure to release previously allocated memory for network queues when the subsequent allocation for cbd_base fails inside fec_enet_init, resulting in a kernel memory leak on error paths.

Why it matters to the business

Progressive memory exhaustion on Linux systems using the FEC Ethernet driver, which can degrade performance, trigger out-of-memory conditions, or cause system instability during repeated interface initialization failures.

How an attack unfolds

An attacker triggers repeated allocation failures during fec_enet_init execution (for example by exhausting memory or inducing specific hardware states) so that queue memory is allocated but never freed, cumulatively depleting kernel memory resources.

How to fix it

Apply the upstream kernel commit that adds the missing kfree calls for the queues on cbd_base allocation failure and returns an error when queue allocation fails; upgrade to a patched mainline or distribution kernel containing the fix.

How to confirm the fix worked

Inspect the fec_enet_init function in the kernel source for proper error-path cleanup of queue structures; run kmemleak or similar kernel memory-leak detectors after exercising the allocation-failure paths.

Typical attack path

1. Identify systems exposing the FEC Ethernet driver
2. Induce memory pressure or allocation failures to reach the error path in fec_enet_init
3. Repeat the triggering condition to accumulate leaked memory
4. Monitor for system-wide memory exhaustion or OOM killer activation

How to detect it

Use kernel memory-leak detectors such as kmemleak to scan for unreleased allocations originating from fec_enet_init; review dmesg and kernel logs for repeated allocation failures around Ethernet controller initialization.

What your security team should do

• Prioritize kernel updates on all systems using the FEC driver
• Enable kernel memory debugging features such as CONFIG_DEBUG_KMEMLEAK in test and production environments
• Monitor overall kernel memory usage and OOM events on affected hosts