CVE-2018-7740 in Linux
Summary
by MITRE
The resv_map_release function in mm/hugetlb.c in the Linux kernel through 4.15.7 allows local users to cause a denial of service (BUG) via a crafted application that makes mmap system calls and has a large pgoff argument to the remap_file_pages system call.
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Analysis
by VulDB Data Team • 09/14/2025
The vulnerability identified as CVE-2018-7740 resides within the Linux kernel's huge page memory management subsystem, specifically in the resv_map_release function located in mm/hugetlb.c. This flaw represents a classic case of improper input validation that can be exploited by local attackers to trigger kernel-level instability. The vulnerability affects Linux kernel versions through 4.15.7, making it a significant concern for systems running these kernel versions where local privilege escalation or denial of service conditions could occur. The issue stems from the kernel's handling of memory mapping operations when large page offset arguments are provided to the remap_file_pages system call, creating a condition where the kernel's internal data structures become corrupted or improperly managed.
The technical exploitation of this vulnerability occurs through a carefully crafted application that leverages the mmap system call in conjunction with the remap_file_pages system call. When an application passes a large pgoff argument to remap_file_pages, the kernel's resv_map_release function fails to properly validate or handle the extreme offset values, leading to memory corruption within the huge page mapping structures. This flaw manifests as a kernel BUG condition, which represents a critical failure in the kernel's memory management subsystem. The vulnerability specifically targets the reservation map management within the huge page implementation, where the kernel maintains tracking information for memory mappings that span large page boundaries. The improper handling of these large offset values causes the kernel to attempt operations on invalid memory locations or to manipulate internal data structures in ways that violate kernel assumptions, ultimately leading to system instability.
The operational impact of CVE-2018-7740 extends beyond simple denial of service to potentially compromise entire system stability and availability. Local users who can execute the malicious application can cause the kernel to crash or enter an unrecoverable state, effectively rendering the system unavailable to legitimate users. This vulnerability can be particularly dangerous in production environments where system uptime is critical, as it allows attackers to perform persistent denial of service attacks that could disrupt services, applications, or even entire infrastructure components. The attack requires local system access but does not require elevated privileges, making it accessible to any user with basic system login capabilities, which significantly broadens the attack surface. From an ATT&CK perspective, this vulnerability aligns with techniques involving privilege escalation and denial of service, potentially enabling adversaries to establish persistent access or disrupt system operations. The vulnerability also relates to CWE-121, which addresses stack-based buffer overflow conditions, though in this case the issue manifests as memory corruption within kernel data structures rather than traditional buffer overflow scenarios.
Mitigation strategies for CVE-2018-7740 primarily involve kernel version upgrades to patched releases where the vulnerability has been addressed through proper input validation and boundary checking within the resv_map_release function. System administrators should prioritize upgrading to kernel versions 4.15.8 or later, where the specific flaw has been corrected through enhanced parameter validation and improved handling of large offset values in memory mapping operations. Additionally, implementing proper system monitoring and intrusion detection mechanisms can help identify exploitation attempts by monitoring for unusual memory mapping patterns or system calls that might indicate malicious activity. Organizations should also consider implementing kernel lockdown mechanisms and restricting local user access where possible, though these measures are not foolproof given that the vulnerability can be exploited through legitimate system calls. The fix typically involves adding proper bounds checking to ensure that pgoff arguments to remap_file_pages do not exceed reasonable limits, preventing the kernel from attempting to process memory mappings that would cause internal data structure corruption. This vulnerability demonstrates the importance of thorough input validation in kernel space operations, where improper handling of edge cases can lead to catastrophic system failures.