CVE-2026-63953 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
mm/migrate_device: fix pgtable leak in migrate_vma_insert_huge_pmd_page
When migrate_vma_insert_huge_pmd_page() jumps to unlock_abort due to a PMD check failure, the pgtable allocated earlier via pte_alloc_one() is never freed, causing a memory leak.
Added free_abort label to release the pgtable in error path.
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Analysis
by VulDB Data Team • 07/20/2026
The vulnerability identified in the Linux kernel's memory management subsystem represents a critical memory leak scenario within the device migration functionality. This issue manifests specifically within the migrate_vma_insert_huge_pmd_page function where improper error handling leads to resource exhaustion. The flaw occurs during the process of migrating virtual memory areas to device memory, a functionality essential for advanced memory management and heterogeneous computing environments. When the PMD check fails, the code path redirects execution to unlock_abort without properly releasing previously allocated page table structures.
The technical root cause stems from inadequate error handling in the memory migration pathway where pte_alloc_one() allocates page table entries but fails to release them when subsequent validation checks fail. This creates a persistent memory leak that accumulates over time, particularly in systems performing frequent memory migration operations. The vulnerability directly impacts the kernel's memory management efficiency and can lead to progressive system degradation as leaked memory resources become unavailable for legitimate allocation requests.
From an operational perspective, this vulnerability compromises system stability and resource utilization within Linux environments that rely heavily on memory migration features. Systems utilizing device memory migration for high-performance computing, graphics processing, or specialized hardware acceleration are particularly susceptible to performance degradation over time. The leak can manifest as reduced available memory, increased memory pressure, and potential system instability under sustained workload conditions where memory migration operations occur frequently.
The mitigation strategy involves implementing proper error path handling through the introduction of a free_abort label that ensures pgtable resources allocated via pte_alloc_one() are released regardless of execution flow. This solution aligns with established security practices for resource management in kernel code and addresses the specific memory leak pattern identified within the Linux kernel's memory subsystem. The fix demonstrates adherence to proper defensive programming principles and represents a standard approach for preventing resource leaks in complex kernel memory management functions.
This vulnerability type falls under CWE-401: Improper Release of Memory Before Removal from Managed Container, which specifically addresses memory management issues in kernel contexts. The issue also relates to ATT&CK technique T1070.004: Indicator Removal on Host - File Deletion, though in this case the resource leak represents a form of system resource depletion rather than direct file deletion. The fix demonstrates proper implementation of error handling patterns that should be applied across similar kernel memory management functions to prevent analogous issues in other subsystems.
The impact extends beyond simple memory consumption as it affects system reliability and can create conditions where legitimate memory allocation requests fail due to exhaustion of available resources. This particularly affects server environments and systems with high memory turnover rates where device migration functionality is frequently utilized for performance optimization. The vulnerability represents a classic example of how improper error handling in kernel code can lead to resource leaks that compound over time, ultimately affecting system stability and performance metrics.
The resolution approach emphasizes the importance of comprehensive error path testing and proper resource cleanup mechanisms in kernel development. This fix serves as a model for similar memory management functions where multiple allocation points exist within conditional execution paths. The implementation ensures that all allocated resources are properly accounted for and released regardless of code execution flow, thereby maintaining system integrity and preventing progressive resource exhaustion issues that could compromise system availability and performance over extended operational periods.