CVE-2026-23097 in Linux
Summary
by MITRE • 02/04/2026
In the Linux kernel, the following vulnerability has been resolved:
migrate: correct lock ordering for hugetlb file folios
Syzbot has found a deadlock (analyzed by Lance Yang):
1) Task (5749): Holds folio_lock, then tries to acquire i_mmap_rwsem(read lock). 2) Task (5754): Holds i_mmap_rwsem(write lock), then tries to acquire folio_lock.
migrate_pages() -> migrate_hugetlbs() -> unmap_and_move_huge_page() <- Takes folio_lock! -> remove_migration_ptes() -> __rmap_walk_file() -> i_mmap_lock_read() <- Waits for i_mmap_rwsem(read lock)!
hugetlbfs_fallocate() -> hugetlbfs_punch_hole() <- Takes i_mmap_rwsem(write lock)! -> hugetlbfs_zero_partial_page() -> filemap_lock_hugetlb_folio() -> filemap_lock_folio() -> __filemap_get_folio <- Waits for folio_lock!
The migration path is the one taking locks in the wrong order according to the documentation at the top of mm/rmap.c. So expand the scope of the existing i_mmap_lock to cover the calls to remove_migration_ptes() too.
This is (mostly) how it used to be after commit c0d0381ade79. That was removed by 336bf30eb765 for both file & anon hugetlb pages when it should only have been removed for anon hugetlb pages.
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Analysis
by VulDB Data Team • 05/03/2026
The vulnerability CVE-2026-23097 represents a critical deadlock condition within the Linux kernel's huge page memory management subsystem, specifically affecting hugetlb file folios. This issue manifests as a classic lock ordering violation that occurs during memory migration operations, creating a scenario where two distinct kernel threads become permanently blocked waiting for each other's locks. The problem stems from an improper sequence in which the kernel acquires locks during the migration process, violating fundamental concurrency control principles that are essential for maintaining system stability and preventing resource starvation.
The technical flaw arises from incorrect lock acquisition order in the memory migration code path for huge page file folios. When a process attempts to migrate huge pages, the kernel must traverse multiple lock acquisition points that are not properly ordered according to the established locking hierarchy defined in the mm/rmap.c file. The deadlock occurs when one thread holds the folio_lock and attempts to acquire the i_mmap_rwsem in read mode, while another thread holds the i_mmap_rwsem in write mode and attempts to acquire the folio_lock. This creates a circular wait condition that can only be resolved by system termination or manual intervention, making it particularly dangerous in production environments where system stability is paramount.
The operational impact of this vulnerability extends beyond simple system hangs, as it affects the core memory management functionality of the Linux kernel. When this deadlock occurs, it can cause entire system processes to freeze, leading to denial of service conditions that may require system rebooting to resolve. The vulnerability particularly affects systems utilizing hugetlbfs filesystems and applications that rely heavily on memory migration operations, including virtualization platforms, high-performance computing environments, and systems managing large memory allocations. This type of deadlock represents a direct violation of the kernel's memory management subsystem reliability requirements and can result in cascading failures across dependent services.
The root cause analysis reveals that this issue was introduced by a previous code change that incorrectly modified lock acquisition patterns for both anonymous and file hugetlb pages, when the modification should have only affected anonymous pages. The commit history shows that the problematic change occurred between c0d0381ade79 and 336bf30eb765, where the lock ordering was relaxed for both page types but should have remained strict for file pages. This modification violated the established locking protocol documented in the kernel's mm/rmap.c source file, which explicitly defines the correct order for acquiring these locks. The fix implemented addresses this by expanding the scope of the existing i_mmap_lock to encompass the remove_migration_ptes() function calls, restoring the proper lock ordering that was previously established.
This vulnerability aligns with CWE-362, which describes a race condition in lock ordering, and demonstrates characteristics consistent with ATT&CK technique T1490, which involves data destruction through system resource exhaustion or corruption. The fix implements a defensive programming approach that restores the original lock ordering behavior for file hugetlb pages while maintaining the intended optimization for anonymous pages. The solution ensures that all memory migration operations follow the documented locking hierarchy, preventing the circular wait condition that leads to system deadlocks. System administrators should prioritize applying this patch to prevent potential denial of service conditions and maintain the stability of memory-intensive applications that rely on hugetlbfs functionality.
The remediation approach taken addresses the fundamental design flaw in the kernel's memory management subsystem by restoring proper lock acquisition semantics. This fix specifically targets the migration path for file folios in the hugetlbfs implementation, ensuring that the i_mmap_rwsem lock is held for the entire duration of the migration operation, including the critical remove_migration_ptes() phase. The solution maintains backward compatibility while preventing the deadlock condition that could otherwise affect production systems. Organizations running Linux systems with hugetlbfs workloads should immediately apply this patch to mitigate the risk of system instability and ensure continued operation of memory-intensive applications.