CVE-2014-8559 in Linux
Summary
by MITRE
The d_walk function in fs/dcache.c in the Linux kernel through 3.17.2 does not properly maintain the semantics of rename_lock, which allows local users to cause a denial of service (deadlock and system hang) via a crafted application.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 02/24/2022
The vulnerability identified as CVE-2014-8559 resides within the Linux kernel's filesystem subsystem, specifically in the d_walk function located in fs/dcache.c. This flaw represents a critical race condition and improper locking mechanism that affects kernel versions through 3.17.2, creating a pathway for local attackers to execute denial of service attacks that can result in complete system hangs. The vulnerability stems from the kernel's inability to properly maintain the semantics of the rename_lock, a crucial synchronization primitive designed to prevent concurrent access to filesystem directory entries during rename operations.
The technical implementation of this vulnerability involves the improper handling of the rename_lock within the d_walk function, which is responsible for walking directory trees and maintaining directory entry consistency. When a malicious application triggers specific conditions through crafted system calls, the function fails to correctly acquire or release the rename_lock, leading to a deadlock scenario where multiple kernel threads become indefinitely blocked waiting for each other to release locks. This improper lock management creates a cascading effect that can propagate throughout the filesystem subsystem, ultimately causing the entire system to become unresponsive and requiring manual intervention or reboot to restore functionality.
From an operational perspective, this vulnerability presents a significant risk to system availability as local users with minimal privileges can exploit it to cause complete system hangs. The attack vector requires only local access to the system, making it particularly dangerous in multi-user environments where privilege escalation might not be necessary. The impact extends beyond simple denial of service as the deadlock conditions can affect critical system services, rendering the system unusable until the affected kernel threads are terminated or the system is rebooted. This vulnerability directly relates to CWE-362, which addresses race conditions in concurrent programming, and aligns with ATT&CK technique T1499.001, which involves network denial of service attacks through resource exhaustion.
The exploitation of this vulnerability demonstrates the critical importance of proper lock management in kernel space operations and highlights the potential for seemingly minor concurrency issues to result in catastrophic system failures. The flaw affects the core filesystem operations that underpin virtually all system functionality, making it particularly dangerous as it can impact any process attempting to perform directory operations. Mitigation strategies include applying the relevant kernel security patches that address the improper lock handling in the d_walk function, implementing kernel lockdown mechanisms to restrict local access, and monitoring for unusual lock contention patterns in system logs. Additionally, system administrators should consider deploying intrusion detection systems that can identify suspicious patterns of filesystem access that might indicate exploitation attempts, while also ensuring that kernel updates are applied promptly to prevent exploitation of this and similar vulnerabilities.