CVE-2011-4098 in Linux
Summary
by MITRE
The fallocate implementation in the GFS2 filesystem in the Linux kernel before 3.2 relies on the page cache, which might allow local users to cause a denial of service by preallocating blocks in certain situations involving insufficient memory.
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Analysis
by VulDB Data Team • 01/03/2022
The vulnerability identified as CVE-2011-4098 represents a critical flaw in the GFS2 (Global File System 2) implementation within the Linux kernel ecosystem. This issue specifically targets the fallocate system call functionality that governs how file systems manage block allocation for files. The GFS2 filesystem, designed for cluster environments where multiple nodes access shared storage, employs a sophisticated approach to file allocation that relies heavily on the kernel's page cache mechanism. When a process attempts to preallocate disk space for a file using fallocate, the system must ensure sufficient memory is available to handle the operation. The vulnerability emerges from the kernel's handling of memory allocation during these preallocation operations, particularly in scenarios where memory resources become constrained.
The technical implementation of this flaw stems from the kernel's reliance on page cache management for GFS2's fallocate operations. When the system attempts to preallocate blocks for a file, it must first ensure adequate memory is available to accommodate the page cache entries required for the operation. In versions of the Linux kernel prior to 3.2, the implementation did not properly handle memory exhaustion conditions during block preallocation. This oversight creates a scenario where local users can exploit the system by initiating fallocate operations that consume excessive memory resources, leading to memory allocation failures that ultimately result in system instability. The vulnerability specifically manifests when the kernel cannot properly manage the memory requirements for page cache entries during concurrent preallocation operations, causing the system to enter a state where it cannot allocate new pages for file operations.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially compromise entire cluster environments that depend on GFS2 for shared storage management. Local users with access to systems running affected kernel versions can exploit this weakness to cause system-wide memory exhaustion, resulting in kernel panics or complete system lockups. The implications are particularly severe in clustered environments where multiple nodes share the same GFS2 filesystem, as a single compromised node could potentially affect the stability of the entire cluster. This vulnerability allows for indirect privilege escalation through resource exhaustion attacks, where attackers can systematically consume memory resources until the system becomes unresponsive to legitimate operations. The attack vector is particularly insidious because it requires only local user access, making it accessible to any user with basic system privileges, and can be executed programmatically to maximize impact.
Mitigation strategies for CVE-2011-4098 primarily focus on kernel version upgrades to Linux kernel 3.2 or later, which contain the necessary patches to address the memory management issues in GFS2's fallocate implementation. System administrators should prioritize updating their kernel versions to ensure protection against this vulnerability, particularly in production environments running GFS2 filesystems. Additional protective measures include implementing memory limits and resource controls to prevent any single process from consuming excessive memory during fallocate operations. The vulnerability aligns with CWE-400, which catalogs weaknesses related to resource exhaustion, and can be mapped to ATT&CK technique T1499.001, which covers network denial of service attacks through resource exhaustion. Organizations should also consider implementing monitoring systems to detect unusual memory consumption patterns that might indicate exploitation attempts, as well as establishing robust patch management procedures to ensure timely deployment of security updates across all systems running affected kernel versions.