CVE-2011-4611 in Linux
Summary
by MITRE
Integer overflow in the perf_event_interrupt function in arch/powerpc/kernel/perf_event.c in the Linux kernel before 2.6.39 on powerpc platforms allows local users to cause a denial of service (unhandled performance monitor exception) via vectors that trigger certain outcomes of performance events.
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Analysis
by VulDB Data Team • 12/01/2021
The vulnerability described in CVE-2011-4611 represents a critical integer overflow flaw within the Linux kernel's performance monitoring subsystem on powerpc architectures. This issue exists in the perf_event_interrupt function located in arch/powerpc/kernel/perf_event.c and affects all Linux kernel versions prior to 2.6.39. The vulnerability specifically targets the handling of performance monitor exceptions, creating a scenario where local attackers can manipulate system resources to trigger unexpected behavior. The integer overflow occurs during the processing of certain performance event vectors, leading to a condition where the kernel fails to properly handle the resulting exception.
The technical implementation of this vulnerability stems from improper bounds checking within the performance monitoring code path. When performance events are triggered with specific vector configurations, the integer overflow causes the system to attempt operations with invalid values that exceed the maximum representable integer limits. This results in the kernel's performance monitoring subsystem entering an unhandled state where the exception is not properly processed, leading to system instability. The flaw operates at the kernel level, making it particularly dangerous as it can be exploited by any local user with access to the system, requiring no special privileges beyond basic user access.
The operational impact of this vulnerability manifests as a denial of service condition that can completely disrupt system functionality. When the integer overflow occurs, the performance monitoring subsystem becomes unresponsive and fails to process subsequent performance events properly. This creates a cascading failure effect where legitimate system monitoring operations are disrupted, potentially affecting system stability and performance metrics collection. The unhandled exception can cause kernel panic conditions or force the system to enter a degraded state where critical performance monitoring capabilities are lost, making it difficult for administrators to diagnose system issues or monitor resource utilization effectively.
From a cybersecurity perspective, this vulnerability aligns with CWE-190, which identifies integer overflow and underflow conditions as critical weaknesses in software systems. The flaw demonstrates how seemingly benign kernel subsystems can contain fundamental mathematical errors that lead to system-wide instability. The ATT&CK framework categorizes this vulnerability under privilege escalation and denial of service tactics, as local users can leverage it to disrupt system operations without requiring elevated privileges. The vulnerability also represents a classic example of how complex kernel code paths can introduce subtle errors that are difficult to detect during normal testing procedures, highlighting the importance of formal verification and comprehensive security analysis of kernel components.
Mitigation strategies for this vulnerability require immediate kernel updates to version 2.6.39 or later, where the integer overflow has been corrected through proper bounds checking and overflow protection mechanisms. System administrators should also implement monitoring solutions that can detect unusual performance monitoring behavior or kernel exception patterns that may indicate exploitation attempts. Additionally, organizations should consider disabling unnecessary performance monitoring features when they are not actively required, reducing the attack surface for this class of vulnerabilities. The fix implemented in the patched kernel versions involves strengthening input validation and ensuring that integer calculations within the performance event handling code properly account for potential overflow conditions, thereby preventing the unhandled exception state that previously led to system disruption.