CVE-2024-40997 in Linux
Summary
by MITRE • 07/12/2024
In the Linux kernel, the following vulnerability has been resolved:
cpufreq: amd-pstate: fix memory leak on CPU EPP exit
The cpudata memory from kzalloc() in amd_pstate_epp_cpu_init() is not freed in the analogous exit function, so fix that.
[ rjw: Subject and changelog edits ]
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Analysis
by VulDB Data Team • 09/29/2024
The vulnerability CVE-2024-40997 represents a memory leak in the Linux kernel's cpufreq subsystem specifically affecting the amd-pstate driver. This issue occurs within the AMD processor power management framework where the kernel fails to properly release allocated memory resources during driver cleanup operations. The flaw manifests in the amd_pstate_epp_cpu_init() function which allocates memory using kzalloc(), a kernel memory allocation function that initializes memory to zero. However, the corresponding cleanup function does not properly invoke the free function to release this allocated memory, creating a persistent memory leak that accumulates over time.
The technical implementation of this vulnerability stems from improper resource management within the AMD p-state CPU frequency driver. When the cpufreq subsystem initializes CPU EPP (Energy Performance Preference) support for AMD processors, it allocates memory structures using kzalloc() to store CPU data. This allocation occurs in the initialization function amd_pstate_epp_cpu_init() but the matching cleanup function fails to release the allocated memory through proper deallocation mechanisms. The memory leak is particularly concerning because it represents a classic resource management error that can lead to progressive memory consumption and potential system instability. This type of vulnerability falls under CWE-401: Improper Release of Memory and aligns with ATT&CK technique T1490: Inhibit System Recovery, as memory exhaustion can lead to system performance degradation and potential denial of service conditions.
The operational impact of this vulnerability extends beyond simple memory consumption issues to potentially affect system stability and performance over extended periods of operation. When the amd-pstate driver is actively managing CPU frequency scaling for AMD processors, the memory leak accumulates with each initialization and cleanup cycle, particularly in systems with frequent CPU frequency transitions or multiple CPU cores. The vulnerability is particularly concerning in server environments or long-running systems where the memory leak can compound over time, leading to reduced available system memory, increased garbage collection pressure, and potential system slowdowns. Additionally, the leak could contribute to memory fragmentation issues that further degrade system performance and may eventually lead to memory allocation failures that could cause system crashes or unexpected behavior.
Mitigation strategies for CVE-2024-40997 focus on applying the kernel patch that properly implements memory deallocation in the amd_pstate_epp_cpu_exit() function. System administrators should prioritize updating their Linux kernel installations to versions that contain the fix, typically kernel versions 6.10 or later where this vulnerability has been addressed. The patch ensures that memory allocated by kzalloc() in the initialization function is properly freed through kfree() calls in the corresponding exit function. Organizations should also implement monitoring systems to detect memory consumption patterns that might indicate memory leaks, particularly in systems running AMD processors with active cpufreq management. Regular kernel updates should be part of the security maintenance routine, and system administrators should verify that their systems are running patched kernel versions to prevent exploitation of this memory leak vulnerability. The fix represents a straightforward resource management correction that prevents the accumulation of memory resources that could otherwise lead to system instability and performance degradation over time.