CVE-2011-2484 in Linux
Summary
by MITRE
The add_del_listener function in kernel/taskstats.c in the Linux kernel 2.6.39.1 and earlier does not prevent multiple registrations of exit handlers, which allows local users to cause a denial of service (memory and CPU consumption), and bypass the OOM Killer, via a crafted application.
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Analysis
by VulDB Data Team • 11/13/2021
The vulnerability identified as CVE-2011-2484 resides within the Linux kernel's taskstats subsystem, specifically in the add_del_listener function located in kernel/taskstats.c. This flaw represents a classic case of improper resource management where the kernel fails to adequately validate or prevent duplicate registrations of exit handlers. The issue affects Linux kernel versions up to and including 2.6.39.1, making it a significant concern for systems running older kernel versions. The root cause stems from the kernel's insufficient input validation mechanisms that allow malicious or crafted applications to register the same exit handler multiple times without proper enforcement of uniqueness constraints.
The technical exploitation of this vulnerability occurs through the deliberate creation of multiple duplicate registrations within the taskstats subsystem. When a local user executes a crafted application that repeatedly registers the same exit handler, the kernel maintains all these duplicate entries in memory without proper cleanup or deduplication. This leads to a progressive accumulation of handler references that consume both memory resources and CPU cycles during the kernel's processing of exit events. The vulnerability's impact extends beyond simple resource exhaustion as it fundamentally undermines the kernel's ability to properly manage system resources through the taskstats interface.
The operational consequences of CVE-2011-2484 are particularly severe as they enable local users to achieve both denial of service conditions and privilege escalation through bypass of critical kernel mechanisms. The memory consumption caused by duplicate handler registrations can quickly exhaust available system resources, leading to system instability and potential crashes. More critically, the vulnerability allows attackers to circumvent the Out-of-Memory Killer mechanism, which is designed to terminate processes that consume excessive memory resources. This bypass capability means that malicious applications can continue consuming system resources indefinitely without being terminated by the kernel's automatic resource management systems, effectively creating a persistent resource drain that can degrade system performance or cause complete system failure.
From a cybersecurity perspective, this vulnerability aligns with CWE-129, which addresses improper validation of array indices, and can be categorized under ATT&CK technique T1499.001 for network denial of service. The flaw demonstrates the importance of proper resource management in kernel space operations and highlights the potential for local privilege escalation through resource exhaustion attacks. Organizations should prioritize kernel updates to address this vulnerability, as the exploitation requires only local access and can be performed by any user with system access. The mitigation strategy involves applying the appropriate kernel security patches that implement proper duplicate detection and prevention mechanisms within the add_del_listener function, ensuring that each exit handler registration is unique and properly tracked to prevent the accumulation of redundant entries that lead to system instability and bypass of critical resource management features.