CVE-2024-27022 in Linux
Summary
by MITRE • 05/01/2024
In the Linux kernel, the following vulnerability has been resolved:
fork: defer linking file vma until vma is fully initialized
Thorvald reported a WARNING [1]. And the root cause is below race:
CPU 1 CPU 2 fork hugetlbfs_fallocate dup_mmap hugetlbfs_punch_hole i_mmap_lock_write(mapping); vma_interval_tree_insert_after -- Child vma is visible through i_mmap tree. i_mmap_unlock_write(mapping); hugetlb_dup_vma_private -- Clear vma_lock outside i_mmap_rwsem! i_mmap_lock_write(mapping); hugetlb_vmdelete_list vma_interval_tree_foreach hugetlb_vma_trylock_write -- Vma_lock is cleared. tmp->vm_ops->open -- Alloc new vma_lock outside i_mmap_rwsem! hugetlb_vma_unlock_write -- Vma_lock is assigned!!! i_mmap_unlock_write(mapping);
hugetlb_dup_vma_private() and hugetlb_vm_op_open() are called outside i_mmap_rwsem lock while vma lock can be used in the same time. Fix this by deferring linking file vma until vma is fully initialized. Those vmas should be initialized first before they can be used.
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Analysis
by VulDB Data Team • 02/07/2026
The vulnerability described in CVE-2024-27022 represents a critical race condition within the Linux kernel's memory management subsystem, specifically affecting the handling of huge page filesystem (hugetlbfs) virtual memory areas during process forking operations. This flaw manifests when a parent process forks a child process while simultaneously performing operations on hugetlbfs files, creating a complex temporal conflict that can lead to memory corruption and system instability. The issue stems from improper locking mechanisms during the duplication of virtual memory areas, where critical operations occur outside the expected synchronization context, creating opportunities for concurrent access violations.
The technical implementation of this vulnerability occurs through a specific race condition between two CPU threads executing different kernel functions. When a process calls fork(), the kernel initiates the dup_mmap operation which acquires the i_mmap_lock_write lock and inserts the child's virtual memory area into the interval tree structure. However, this insertion occurs before the virtual memory area is fully initialized, creating a window where other threads can access the partially constructed vma. Meanwhile, a second thread executing hugetlbfs_fallocate or hugetlbfs_punch_hole operations attempts to manipulate the same memory structures while holding different locking mechanisms, leading to inconsistent state management. The core flaw lies in the fact that hugetlb_dup_vma_private() and hugetlb_vm_op_open() functions are executed outside the i_mmap_rwsem lock context, while vma_lock operations can occur simultaneously, causing the vma_lock to be cleared and reassigned during critical operations.
This vulnerability has significant operational impact on systems running Linux kernels, particularly those utilizing hugetlbfs for high-performance applications, database systems, and memory-intensive workloads. The race condition can result in memory corruption, kernel panics, and system crashes that may be difficult to reproduce consistently, making it particularly dangerous for production environments. The flaw affects the integrity of virtual memory management structures, potentially allowing for privilege escalation attacks or denial of service conditions. Systems with heavy concurrent access to huge page filesystems are most vulnerable, as the timing requirements for the race condition to manifest are more easily met under high load conditions.
The fix implemented for CVE-2024-27022 addresses the fundamental synchronization issue by deferring the linking of file virtual memory areas until the vma is fully initialized. This approach ensures that all necessary initialization steps occur within the proper locking context before the virtual memory area becomes visible to other threads. The solution follows established kernel development practices for managing concurrent access to shared data structures and aligns with the principles of proper lock ordering and resource management. This remediation prevents the race condition by ensuring that the i_mmap_rwsem lock is held throughout the complete vma initialization and linking process, preventing concurrent access to partially constructed memory management structures. The fix also relates to CWE-362, which describes a race condition in concurrent execution, and maps to ATT&CK technique T1068, which covers privilege escalation through kernel vulnerabilities, though the specific impact is more focused on system stability and memory corruption rather than direct privilege escalation.