CVE-2012-1146 in Linux
Summary
by MITRE
The mem_cgroup_usage_unregister_event function in mm/memcontrol.c in the Linux kernel before 3.2.10 does not properly handle multiple events that are attached to the same eventfd, which allows local users to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact by registering memory threshold events.
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Analysis
by VulDB Data Team • 03/22/2021
The vulnerability identified as CVE-2012-1146 resides within the Linux kernel's memory control subsystem, specifically in the mem_cgroup_usage_unregister_event function located in mm/memcontrol.c. This flaw represents a critical security issue that affects Linux kernel versions prior to 3.2.10, where the kernel fails to properly manage eventfd references when multiple events are attached to the same eventfd descriptor. The root cause stems from inadequate handling of reference counting and event management within the memory cgroup subsystem, creating a scenario where improper event registration can lead to system instability.
The technical exploitation of this vulnerability occurs when local users register multiple memory threshold events against the same eventfd descriptor. The mem_cgroup_usage_unregister_event function does not correctly account for multiple event attachments to a single eventfd, resulting in improper reference counting behavior. When the system attempts to unregister these events, the function encounters a NULL pointer dereference condition due to the corrupted eventfd reference structure. This NULL pointer dereference ultimately leads to a kernel oops or system crash, effectively causing a denial of service condition that can bring the entire system to a halt.
From an operational perspective, this vulnerability presents significant risks to system availability and stability in environments where memory cgroup monitoring is actively used. The denial of service impact can be particularly severe in containerized environments or systems that rely heavily on memory resource management and monitoring. Attackers can exploit this vulnerability without requiring elevated privileges, making it a serious concern for any Linux system running vulnerable kernel versions. The potential for unspecified other impacts exists because the NULL pointer dereference could potentially be leveraged to execute arbitrary code under certain conditions, though this remains theoretical and dependent on additional system configurations.
This vulnerability maps to CWE-476, which describes NULL pointer dereference conditions in software systems. The flaw demonstrates poor resource management practices within the kernel's memory control group implementation and aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through kernel-level vulnerabilities. The issue highlights the importance of proper reference counting mechanisms and event management in kernel space, where improper handling can lead to system crashes and availability disruptions. Organizations should prioritize patching affected systems to address this vulnerability, as it represents a fundamental flaw in the kernel's memory management subsystem that can be exploited to cause system instability and potential service interruptions.
The remediation strategy involves upgrading to Linux kernel version 3.2.10 or later, where the mem_cgroup_usage_unregister_event function has been corrected to properly handle multiple events attached to the same eventfd. System administrators should also consider implementing monitoring solutions to detect unusual memory cgroup activity that might indicate exploitation attempts. Additionally, organizations should review their memory management configurations and ensure proper eventfd handling in applications that interact with memory cgroup interfaces to minimize the risk of triggering this vulnerability through legitimate system operations.