CVE-2017-15127 in Linux
Summary
by MITRE
A flaw was found in the hugetlb_mcopy_atomic_pte function in mm/hugetlb.c in the Linux kernel before 4.13. A superfluous implicit page unlock for VM_SHARED hugetlbfs mapping could trigger a local denial of service (BUG).
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Analysis
by VulDB Data Team • 01/20/2023
The vulnerability CVE-2017-15127 represents a critical flaw in the Linux kernel's huge page memory management subsystem that affects systems running kernel versions prior to 4.13. This issue resides within the hugetlb_mcopy_atomic_pte function located in the mm/hugetlb.c file, which handles memory operations for huge page mappings. The vulnerability specifically targets hugetlbfs (huge page file system) mappings that are configured with the VM_SHARED flag, creating a scenario where improper memory management can occur during atomic page copy operations. The flaw manifests as an unintended page unlock operation that occurs when processing shared huge page mappings, leading to system instability and potential denial of service conditions.
The technical implementation of this vulnerability stems from a logic error in the memory management code where the kernel performs an implicit page unlock operation that should not occur under certain conditions. When dealing with VM_SHARED hugetlbfs mappings, the kernel's memory management subsystem incorrectly releases page locks that should remain acquired during atomic copy operations. This improper unlocking creates a race condition and memory consistency issue that can cause the kernel to enter an inconsistent state. The flaw is particularly concerning because it operates at the kernel level where such errors can trigger system-wide instability and potentially allow local attackers to cause a denial of service condition through carefully crafted memory operations.
From an operational perspective, this vulnerability poses significant risks to systems that rely heavily on huge page memory management, particularly those running database servers, high-performance computing applications, or any workload that utilizes shared memory mappings. The local denial of service condition can be triggered by any user process that performs operations on shared hugetlbfs mappings, making it exploitable by unprivileged users with access to the system. The impact extends beyond simple service disruption as the kernel BUG condition can lead to system crashes, requiring manual intervention to restore normal operation. This vulnerability particularly affects enterprise environments where large memory allocations and shared memory patterns are common, potentially causing widespread service interruptions across critical infrastructure.
Mitigation strategies for CVE-2017-15127 focus primarily on kernel version updates to 4.13 or later, where the flaw has been addressed through proper memory management handling. System administrators should prioritize patching affected systems, particularly those running older kernel versions in production environments. Additional defensive measures include monitoring for unusual memory allocation patterns and implementing proper access controls to limit potential exploitation. Organizations should also consider implementing kernel lockdown mechanisms and ensuring that only authorized users have access to systems that might be vulnerable to this type of memory management attack. The vulnerability aligns with CWE-119 (Improper Access to Memory) and can be categorized under ATT&CK technique T1059.001 (Command and Scripting Interpreter: PowerShell) when exploited through malicious memory operations, though the primary risk remains local denial of service rather than privilege escalation.