CVE-2011-2689 in Linux
Summary
by MITRE
The gfs2_fallocate function in fs/gfs2/file.c in the Linux kernel before 3.0-rc1 does not ensure that the size of a chunk allocation is a multiple of the block size, which allows local users to cause a denial of service (BUG and system crash) by arranging for all resource groups to have too little free space.
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Analysis
by VulDB Data Team • 12/02/2024
The vulnerability described in CVE-2011-2689 represents a critical flaw in the Linux kernel's gfs2 file system implementation that affects systems using the Global File System 2. This issue stems from improper handling of chunk allocation sizes within the gfs2_fallocate function located in fs/gfs2/file.c. The flaw manifests when the kernel fails to validate that allocated chunk sizes align with the underlying block size requirements, creating a scenario where memory management operations can lead to system instability. The vulnerability specifically impacts Linux kernel versions prior to 3.0-rc1, indicating that this was a known issue that required kernel-level patching to resolve.
The technical execution of this vulnerability involves a local attacker who can manipulate file allocation operations to force the kernel into a state where resource groups become critically under-resourced. When the gfs2_fallocate function processes allocation requests without proper block size alignment, it can cause cascading failures within the file system's resource management subsystem. This misalignment leads to situations where the system's free space accounting becomes corrupted, ultimately resulting in kernel BUG messages and complete system crashes. The flaw operates at the kernel level, making it particularly dangerous as it can be exploited without requiring elevated privileges beyond normal user access.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromising entire system stability. When exploited, the vulnerability can cause unpredictable system behavior including kernel panics, system lockups, and complete system crashes that require manual rebooting. This makes it particularly dangerous in production environments where system uptime is critical, as local users could intentionally trigger these conditions to disrupt services. The vulnerability's nature suggests it could be leveraged in combination with other exploits to create more sophisticated attack vectors targeting system availability.
Mitigation strategies for CVE-2011-2689 primarily focus on kernel version updates and system hardening measures. Organizations should immediately upgrade to Linux kernel versions 3.0-rc1 or later where this vulnerability has been addressed through proper validation of chunk allocation sizes against block boundaries. System administrators should also implement monitoring solutions to detect unusual allocation patterns that might indicate exploitation attempts. From a cybersecurity perspective, this vulnerability aligns with CWE-129, which addresses improper validation of array index values, and could be categorized under ATT&CK technique T1499 for network denial of service attacks. The flaw demonstrates the importance of proper input validation in kernel space operations and highlights the critical need for thorough testing of file system allocation routines. Additionally, implementing proper resource group management policies and monitoring free space utilization patterns can help detect and prevent exploitation attempts before they cause system crashes.