CVE-2011-2918 in Linux
Summary
by MITRE
The Performance Events subsystem in the Linux kernel before 3.1 does not properly handle event overflows associated with PERF_COUNT_SW_CPU_CLOCK events, which allows local users to cause a denial of service (system hang) via a crafted application.
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Analysis
by VulDB Data Team • 08/18/2024
The vulnerability identified as CVE-2011-2918 resides within the Linux kernel's Performance Events subsystem, specifically affecting versions prior to 3.1. This flaw manifests in the improper handling of event overflows related to PERF_COUNT_SW_CPU_CLOCK events, which are part of the kernel's performance monitoring capabilities. The Performance Events subsystem provides a unified interface for accessing hardware and software performance counters, enabling applications and system tools to monitor various aspects of system behavior including CPU cycles, cache misses, and other performance metrics. The vulnerability represents a critical design flaw in the kernel's event handling mechanisms that can be exploited by local attackers to disrupt system operations.
The technical implementation of this vulnerability stems from inadequate overflow handling within the kernel's performance monitoring framework. When PERF_COUNT_SW_CPU_CLOCK events reach their maximum count and overflow, the kernel fails to properly manage the overflow condition, leading to a system hang or complete denial of service. This occurs because the kernel's event processing logic does not correctly reset or reinitialize the performance counter state upon overflow, causing the system to become unresponsive. The flaw is particularly concerning because it operates at the kernel level, meaning that a local user with minimal privileges can exploit this vulnerability to cause system-wide disruption without requiring administrative access or elevated privileges.
The operational impact of CVE-2011-2918 extends beyond simple system hangs, potentially affecting system availability and reliability in production environments. Local attackers can craft malicious applications that repeatedly trigger performance events until the overflow condition occurs, effectively bringing the system to a halt. This type of vulnerability is particularly dangerous in server environments where system uptime is critical, as it can be used to perform denial of service attacks against running services. The vulnerability also represents a weakness in the kernel's resource management and error handling procedures, highlighting the importance of proper state management in kernel-level subsystems.
This vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and demonstrates the broader category of improper handling of overflow conditions in kernel space. From an ATT&CK perspective, this vulnerability maps to T1499.004, which covers "Network Denial of Service," although in this case the attack vector is local rather than network-based. The flaw also corresponds to T1059.001, representing command and scripting interpreter usage, as attackers may need to craft specific applications or scripts to trigger the vulnerability. The mitigation strategy involves upgrading to kernel versions 3.1 or later where the vulnerability has been addressed through proper overflow handling mechanisms. Additionally, system administrators should implement monitoring for unusual performance counter activity and consider restricting access to performance monitoring interfaces when possible, though this may impact legitimate diagnostic and profiling activities. The fix implemented in kernel 3.1 ensures proper state management during overflow conditions, preventing the system hang that occurred previously and maintaining system stability under normal operating conditions.