CVE-2011-3982 in AIX
Summary
by MITRE
The Fibre Channel driver for QLogic adapters in IBM AIX 6.1 and 7.1 does not properly handle DMA resource limitations, which allows local users to cause a denial of service (system hang) via vectors that generate a large amount of DMA I/O, related to a deadlock in timer processing across CPUs.
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Analysis
by VulDB Data Team • 04/13/2019
The vulnerability identified as CVE-2011-3982 represents a critical flaw in the Fibre Channel driver implementation for QLogic adapters within IBM AIX operating systems version 6.1 and 7.1. This issue stems from inadequate handling of Direct Memory Access resource limitations, creating a scenario where local malicious users can exploit the system's DMA I/O processing capabilities to trigger system-level denial of service conditions. The flaw manifests specifically during high-volume DMA I/O operations when the system encounters resource exhaustion and subsequent deadlock conditions in timer processing across multiple Central Processing Units.
The technical root cause of this vulnerability lies in the improper resource management within the Fibre Channel driver's DMA handling mechanisms. When large volumes of DMA I/O operations are initiated through specific vectors, the driver fails to adequately manage the limited DMA resources available on the system. This resource mismanagement creates a condition where timer processing functions become deadlocked across multiple CPU cores, effectively freezing the system's ability to process further I/O operations. The vulnerability operates at the kernel level within the storage subsystem, making it particularly dangerous as it can bring entire system operations to a halt without requiring external network access or elevated privileges beyond local user access.
The operational impact of this vulnerability extends beyond simple system unresponsiveness, as it creates a persistent denial of service condition that can severely disrupt mission-critical applications relying on Fibre Channel storage connectivity. Local users with minimal privileges can exploit this weakness to cause system hangs that may require manual intervention or system reboot to resolve. The distributed nature of the deadlock across multiple CPUs makes the system recovery process more complex and time-consuming, potentially leading to extended downtime for enterprise environments where storage availability is paramount. This vulnerability particularly affects environments using QLogic Fibre Channel adapters in IBM AIX systems where high-volume I/O operations are common.
From a cybersecurity perspective, this vulnerability aligns with CWE-362, which describes concurrent execution using shared resource vulnerabilities, and represents a classic example of resource exhaustion leading to system instability. The ATT&CK framework categorizes this as a system denial of service technique, where adversaries leverage system resource limitations to compromise availability. Organizations should implement immediate mitigations including applying the relevant IBM AIX patches and updates that address the DMA resource handling in the Fibre Channel driver. System administrators should also consider monitoring for unusual DMA I/O patterns and implementing proper resource limits for I/O operations to prevent exploitation. Additionally, maintaining updated system configurations and regularly reviewing system logs for potential exploitation attempts can help detect and prevent successful attacks against this vulnerability.