CVE-2024-40997

What it actually does

Memory leak in amd-pstate EPP driver where kzalloc-allocated cpudata in amd_pstate_epp_cpu_init is never released by the exit path.

Why it matters to the business

Gradual memory exhaustion on AMD-based Linux systems can degrade performance and eventually cause instability or outages if the driver is repeatedly initialized and torn down.

How an attack unfolds

An attacker with local access triggers repeated CPU EPP governor attach/detach cycles through power-management or CPU hotplug interfaces to accumulate unreleased kernel memory until the system is impaired.

How to fix it

Apply a kernel containing commit 448efb7ea0bfa2c4e27c5a2eb5684fd225cd12cd (or equivalent stable backport) and rebuild or install the updated package; for packaged distributions, upgrade to the corresponding fixed release.

How to confirm the fix worked

Confirm the fix is present by inspecting the amd_pstate_epp.c source for the matching free call after amd_pstate_epp_cpu_exit or by booting the patched kernel and verifying no leak under repeated EPP init/exit cycles.

Typical attack path

1. Obtain local access on an affected AMD Linux system
2. Repeatedly load/unload or reconfigure the amd_pstate_epp cpufreq driver
3. Observe progressive kernel memory growth until resource pressure occurs

How to detect it

Watch kernel logs and memory accounting for repeated amd_pstate_epp_cpu_init allocations without corresponding frees; profile slab usage for cpudata objects tied to the EPP driver under load.

What your security team should do

• Prioritize kernel updates on all AMD systems running the EPP governor
• Add memory-usage alerting for cpufreq-related allocations
• Review and restrict unprivileged access to CPU frequency and hotplug interfaces