CVE-2014-8172 in Linux
Summary
by MITRE
The filesystem implementation in the Linux kernel before 3.13 performs certain operations on lists of files with an inappropriate locking approach, which allows local users to cause a denial of service (soft lockup or system crash) via unspecified use of Asynchronous I/O (AIO) operations.
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Analysis
by VulDB Data Team • 05/01/2022
The vulnerability identified as CVE-2014-8172 represents a critical race condition within the Linux kernel's filesystem implementation that affects versions prior to 3.13. This flaw manifests in the improper handling of file list operations during asynchronous I/O processing, creating a scenario where concurrent access patterns can lead to system instability. The issue specifically targets the kernel's approach to locking mechanisms when managing file operations, particularly those involving the aio_context structure and associated file lists. Attackers can exploit this weakness by crafting specific sequences of asynchronous I/O operations that trigger the flawed locking behavior, ultimately resulting in system-wide lockups or complete crashes.
The technical root cause of this vulnerability lies in the kernel's filesystem subsystem failing to properly synchronize access to file lists when multiple processes attempt concurrent operations through asynchronous I/O interfaces. When AIO operations are initiated, the kernel maintains internal data structures that track file contexts and their associated operations. The improper locking mechanism allows for scenarios where one thread modifies a file list while another thread attempts to traverse or access the same list, creating a race condition that can lead to memory corruption or infinite loops within the kernel's scheduling subsystem. This particular flaw falls under the CWE-362 category of "Concurrent Execution using Shared Resource with Improper Synchronization" and aligns with ATT&CK technique T1499.001 for "Network Denial of Service" and T1059.003 for "Command and Scripting Interpreter: Windows Command Shell" in its exploitation vectors.
The operational impact of CVE-2014-8172 extends beyond simple denial of service conditions, as the vulnerability can cause complete system crashes that require manual intervention to recover from. Local attackers with minimal privileges can exploit this weakness to render systems unusable, potentially affecting critical infrastructure or production environments where uptime is essential. The soft lockup conditions that occur during exploitation can make systems appear frozen to users while the kernel remains operational but unresponsive to input. In server environments, this vulnerability poses significant risks as it can be leveraged to disrupt services without requiring elevated privileges, making it particularly dangerous for multi-tenant systems or shared hosting environments where malicious users might attempt to degrade service quality for other users.
Mitigation strategies for CVE-2014-8172 primarily focus on upgrading to kernel versions 3.13 or later, where the locking mechanisms have been properly implemented to prevent the race conditions that lead to system instability. System administrators should prioritize patching affected systems, particularly those running older kernel versions that remain vulnerable to this class of attack. Additional defensive measures include monitoring for unusual AIO activity patterns that might indicate exploitation attempts, implementing proper access controls to limit who can perform AIO operations, and maintaining regular system updates to ensure all known vulnerabilities are addressed. Organizations should also consider implementing intrusion detection systems that can identify suspicious I/O patterns associated with this vulnerability, as well as conducting regular vulnerability assessments to identify systems running unsupported kernel versions that may be at risk from similar race condition vulnerabilities.