CVE-2007-4133 in Linux
Summary
by MITRE
The (1) hugetlb_vmtruncate_list and (2) hugetlb_vmtruncate functions in fs/hugetlbfs/inode.c in the Linux kernel before 2.6.19-rc4 perform certain prio_tree calculations using HPAGE_SIZE instead of PAGE_SIZE units, which allows local users to cause a denial of service (panic) via unspecified vectors.
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Analysis
by VulDB Data Team • 07/27/2019
The vulnerability identified as CVE-2007-4133 represents a critical flaw in the Linux kernel's huge page memory management subsystem that affects versions prior to 2.6.19-rc4. This issue resides within the hugetlbfs filesystem implementation where two specific functions hugetlb_vmtruncate_list and hugetlb_vmtruncate exhibit improper memory calculation behavior. The flaw stems from the incorrect application of memory size units during prio_tree operations, which are fundamental data structures used for managing memory mappings in the kernel's virtual memory subsystem. When these functions process huge page allocations, they utilize HPAGE_SIZE units instead of the standard PAGE_SIZE units that are expected by the underlying memory management algorithms. This discrepancy creates a fundamental mismatch in how memory regions are tracked and managed within the kernel's memory subsystem.
The technical execution of this vulnerability occurs when local users manipulate huge page memory mappings through the hugetlbfs filesystem interface. The improper calculation using HPAGE_SIZE instead of PAGE_SIZE causes the kernel's memory management routines to miscalculate the boundaries and relationships between memory regions stored in the prio_tree data structures. This miscalculation leads to memory corruption within the kernel's virtual memory management code, specifically in how it tracks and manages huge page mappings. The vulnerability manifests as a kernel panic, which represents a complete system crash that terminates all running processes and requires system reboot. The panic occurs because the kernel's memory management subsystem encounters inconsistent data structures that violate internal assumptions about memory region boundaries and relationships.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a fundamental flaw in the kernel's memory management architecture that could potentially be exploited to destabilize systems running vulnerable kernel versions. Local users with access to the system can trigger this condition through various means involving huge page operations, including file system operations on hugetlbfs mounts or direct memory mapping operations. The vulnerability affects systems that utilize huge page memory management features, which are commonly found in high-performance computing environments, database servers, and applications requiring large memory allocations. From a cybersecurity perspective, this vulnerability aligns with attack patterns described in the ATT&CK framework under privilege escalation and denial of service categories, as it allows local users to escalate their privileges to kernel level and cause system-wide outages.
The root cause of this vulnerability maps directly to CWE-129, which describes improper validation of array index values, and CWE-131, which covers improper handling of memory allocation sizes. The flaw represents a classic case of incorrect unit usage in kernel memory management code where the distinction between page sizes creates cascading failures in memory tracking mechanisms. The vulnerability demonstrates the critical importance of maintaining consistency in memory management operations across different kernel subsystems and highlights the potential for seemingly minor unit conversion errors to cause catastrophic system failures. Mitigation strategies include upgrading to kernel versions 2.6.19-rc4 or later where the issue has been resolved, implementing proper kernel patch management procedures, and monitoring for suspicious memory allocation patterns that might indicate exploitation attempts. Additionally, system administrators should consider disabling hugetlbfs functionality if it is not required for specific applications, thereby reducing the attack surface while maintaining overall system security posture.