CVE-2001-0062 in FreeBSD
Summary
by MITRE
procfs in FreeBSD and possibly other operating systems allows local users to cause a denial of service by calling mmap on the process own mem file, which causes the kernel to hang.
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Analysis
by VulDB Data Team • 05/29/2018
The vulnerability identified as CVE-2001-0062 represents a critical denial of service flaw within the FreeBSD operating system's procfs implementation and potentially affects other Unix-like systems. This vulnerability resides in the kernel's handling of memory mapping operations on process memory files, specifically targeting the interaction between user-space applications and the virtual file system that exposes process information. The flaw manifests when a local user process attempts to invoke the mmap system call on its own memory file within the procfs, leading to a kernel hang that effectively renders the system unresponsive to further operations. This type of vulnerability falls under the category of kernel-level flaws that can severely impact system availability and stability.
The technical root cause of this vulnerability stems from improper validation and handling of memory mapping requests within the procfs subsystem. When a process attempts to map its own memory file using mmap, the kernel's memory management subsystem fails to properly handle this specific edge case, resulting in an infinite loop or deadlock condition within kernel space. The vulnerability exploits the interaction between the virtual file system implementation and the memory management subsystem, where the kernel's internal data structures become corrupted or locked in an inconsistent state. This flaw demonstrates a classic case of insufficient input validation and error handling in kernel code, where the expected behavior for normal memory mapping operations conflicts with the special case of mapping one's own memory file, leading to a complete system hang.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a fundamental weakness in the kernel's memory management capabilities that could potentially be exploited by malicious users to disrupt system operations. Local users with access to the system can leverage this vulnerability to cause system-wide hangs, requiring manual intervention or system reboot to restore normal operation. The implications are particularly severe in multi-user environments where a single compromised account could potentially affect the entire system's availability. This vulnerability also highlights the importance of proper kernel resource management and the potential for seemingly benign operations to trigger catastrophic failures in operating system internals.
Mitigation strategies for this vulnerability should focus on kernel-level patches that properly validate memory mapping requests and prevent the specific scenario that leads to the kernel hang. System administrators should implement immediate updates to their FreeBSD systems to address this vulnerability, as the flaw affects the core kernel functionality and cannot be adequately protected through user-space measures alone. The recommended approach includes applying the official FreeBSD security patches that modify the procfs implementation to properly handle mmap requests on process memory files. Additionally, organizations should consider implementing monitoring solutions that can detect abnormal kernel behavior patterns and provide early warning of potential exploitation attempts. This vulnerability serves as a reminder of the critical importance of kernel security testing and validation, particularly for virtual file system implementations that provide access to sensitive system information. The flaw aligns with CWE-121, which addresses buffer overflow conditions in kernel space, and represents a specific instance where improper resource handling leads to system instability. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation and denial of service tactics, as it allows local users to disrupt system operations without requiring elevated privileges, demonstrating how kernel-level flaws can be leveraged to achieve system-wide impact through seemingly simple operations.