CVE-2011-1747 in Linux
Summary
by MITRE
The agp subsystem in the Linux kernel 2.6.38.5 and earlier does not properly restrict memory allocation by the (1) AGPIOC_RESERVE and (2) AGPIOC_ALLOCATE ioctls, which allows local users to cause a denial of service (memory consumption) by making many calls to these ioctls.
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Analysis
by VulDB Data Team • 11/06/2021
The vulnerability identified as CVE-2011-1747 resides within the Accelerated Graphics Port AGP subsystem of the Linux kernel version 2.6.38.5 and earlier. This flaw represents a critical memory management issue that affects the kernel's graphics hardware abstraction layer, specifically targeting the AGPIOC_RESERVE and AGPIOC_ALLOCATE ioctls. These ioctls are designed to manage memory allocation for graphics hardware acceleration, but they fail to implement proper validation mechanisms to restrict the amount of memory that can be allocated through these interfaces.
The technical flaw manifests in the improper handling of memory allocation requests through the AGP subsystem's ioctl interface. When local users execute multiple calls to the AGPIOC_RESERVE and AGPIOC_ALLOCATE ioctls, the kernel fails to enforce adequate limits on memory consumption, allowing attackers to continuously request memory resources without proper bounds checking. This design deficiency stems from a lack of input validation and resource management controls within the kernel's graphics hardware management code, creating a condition where memory allocation requests can be made without proper authorization or resource limitation enforcement.
The operational impact of this vulnerability is significant, as it enables local users to perform a denial of service attack by consuming excessive system memory resources. This memory exhaustion can lead to system instability, application crashes, and potentially complete system hangs or reboots, particularly in environments where graphics hardware acceleration is actively used. The vulnerability is particularly dangerous because it requires no special privileges beyond local access, making it an attractive target for malicious users who wish to disrupt system operations without elevated permissions. The attack vector is straightforward and can be executed repeatedly, making it difficult to defend against through simple monitoring or detection mechanisms.
From a cybersecurity perspective, this vulnerability aligns with CWE-772, which addresses the weakness of missing resource exhaustion protection, and represents a classic example of insufficient resource management in kernel space operations. The attack pattern follows the principles outlined in the MITRE ATT&CK framework under the technique of privilege escalation and denial of service, where local users can leverage kernel-level weaknesses to compromise system availability. The vulnerability demonstrates the critical importance of proper input validation and resource limitation in kernel modules, particularly those dealing with hardware-specific interfaces that require direct memory management. Organizations should implement immediate patching strategies to address this vulnerability, as the risk of exploitation increases with the complexity of graphics workloads and the number of concurrent users on affected systems. System administrators should also monitor for unusual memory consumption patterns and consider implementing resource limits on graphics-related processes to mitigate potential exploitation scenarios.