CVE-2008-4302 in Linux
Summary
by MITRE
fs/splice.c in the splice subsystem in the Linux kernel before 2.6.22.2 does not properly handle a failure of the add_to_page_cache_lru function, and subsequently attempts to unlock a page that was not locked, which allows local users to cause a denial of service (kernel BUG and system crash), as demonstrated by the fio I/O tool.
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Analysis
by VulDB Data Team • 12/22/2024
The vulnerability identified as CVE-2008-4302 resides within the Linux kernel's splice subsystem, specifically in the fs/splice.c file, affecting kernel versions prior to 2.6.22.2. This flaw represents a critical issue in kernel memory management and resource handling that can be exploited by local attackers to induce system crashes and denial of service conditions. The vulnerability manifests when the kernel's splice operation fails to properly manage page cache operations, creating a scenario where kernel resources become inconsistent and lead to system instability.
The technical root cause of this vulnerability stems from improper error handling within the add_to_page_cache_lru function, which is responsible for managing page cache entries in the kernel's memory management system. When this function fails during a splice operation, the kernel code path does not adequately account for the failure condition, leading to a subsequent attempt to unlock a memory page that was never actually locked. This creates a kernel BUG condition where the kernel's internal consistency checks detect an invalid state and trigger a system crash. The flaw operates at the kernel level where memory management and page cache operations intersect, making it particularly dangerous as it can cause complete system instability.
The operational impact of CVE-2008-4302 is significant for local attackers who can leverage this vulnerability to perform denial of service attacks against Linux systems. The demonstration using the fio I/O tool shows how readily exploitable this vulnerability is in real-world scenarios, as it requires only local access to trigger the problematic code path. When exploited, the vulnerability results in kernel BUG messages being logged to system logs and ultimately causes the system to crash and reboot, effectively denying service to legitimate users and applications. This type of vulnerability is particularly concerning in production environments where system availability is critical, as it can be used to disrupt services without requiring external network access.
From a cybersecurity perspective, this vulnerability aligns with CWE-248, which addresses "Uncaught Exception" in software systems, and relates to ATT&CK technique T1499.004 for "Endpoint Denial of Service" where adversaries can cause system instability through kernel-level flaws. The vulnerability demonstrates the importance of proper error handling in kernel code, particularly when dealing with memory management operations that must maintain strict consistency. Mitigation strategies include updating to kernel versions 2.6.22.2 or later where the fix has been implemented, which properly handles the error condition in add_to_page_cache_lru and prevents the invalid page unlock operation. System administrators should also consider implementing monitoring for kernel BUG messages and ensure regular kernel updates are applied to protect against similar vulnerabilities in the kernel's memory management subsystem. The vulnerability serves as a reminder of the critical nature of kernel-level security and the potential for seemingly minor error handling issues to result in catastrophic system failures.