CVE-2012-2133 in Linux
Summary
by MITRE
Use-after-free vulnerability in the Linux kernel before 3.3.6, when huge pages are enabled, allows local users to cause a denial of service (system crash) or possibly gain privileges by interacting with a hugetlbfs filesystem, as demonstrated by a umount operation that triggers improper handling of quota data.
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Analysis
by VulDB Data Team • 03/24/2021
The vulnerability described in CVE-2012-2133 represents a critical use-after-free condition within the Linux kernel's handling of huge pages and hugetlbfs filesystem operations. This flaw exists in kernel versions prior to 3.3.6 and specifically manifests when huge pages are enabled in the system configuration. The vulnerability stems from improper memory management during umount operations on hugetlbfs filesystems, where the kernel fails to correctly handle quota data structures, leading to memory corruption scenarios that can be exploited by local attackers.
The technical implementation of this vulnerability involves the kernel's memory allocation and deallocation mechanisms within the huge page subsystem. When a hugetlbfs filesystem is mounted and subsequently unmounted, the kernel's quota management code attempts to free memory structures that have already been released or are in an inconsistent state. This use-after-free condition creates opportunities for memory corruption that can be leveraged to either crash the system through denial of service or potentially escalate privileges through controlled memory corruption. The flaw specifically affects the interaction between the hugetlbfs filesystem implementation and the quota subsystem, where memory pointers become invalid during the cleanup process.
From an operational impact perspective, this vulnerability presents significant risks to system stability and security integrity. Local attackers with minimal privileges can trigger system crashes that result in denial of service conditions, disrupting critical services and potentially enabling persistent attacks through repeated exploitation attempts. The privilege escalation aspect, while not fully confirmed in all scenarios, suggests that under certain conditions an attacker might be able to manipulate memory layout and execute arbitrary code with elevated privileges. This makes the vulnerability particularly dangerous in multi-tenant environments or systems where local access cannot be strictly controlled.
The exploitation of this vulnerability aligns with several attack patterns documented in the attack tactics and techniques framework, particularly those involving privilege escalation and denial of service. The use-after-free condition maps directly to common software security weaknesses categorized under CWE-416, which deals with use after free vulnerabilities. The specific context of huge page handling and filesystem operations places this vulnerability within the broader category of kernel memory management flaws that can be exploited through carefully crafted system calls. Organizations should implement immediate mitigations including kernel updates to version 3.3.6 or later, which contain the necessary patches to address the improper memory handling during hugetlbfs operations. Additionally, system administrators should consider disabling huge pages for systems where this vulnerability cannot be immediately patched, though this may impact performance in memory-intensive applications. The vulnerability demonstrates the critical importance of proper memory management in kernel space and highlights the need for comprehensive testing of filesystem operations, particularly those involving complex memory allocation patterns and resource cleanup procedures.