CVE-2026-80879 in Linux
Summary
by MITRE • 09/04/2026
In the Linux kernel, the following vulnerability has been resolved:
ocfs2: fix circular locking dependency in ocfs2_dio_end_io_write
A circular locking dependency involves INODE_ALLOC_SYSTEM_INODE, EXTENT_ALLOC_SYSTEM_INODE, and ORPHAN_DIR_SYSTEM_INODE.
1. ocfs2_mknod() acquires INODE_ALLOC then EXTENT_ALLOC.
2. ocfs2_dio_end_io_write() acquires EXTENT_ALLOC for unwritten extents, then ORPHAN_DIR via ocfs2_del_inode_from_orphan() while still holding EXTENT_ALLOC.
3. ocfs2_wipe_inode() acquires ORPHAN_DIR then INODE_ALLOC via ocfs2_remove_inode.
Break the cycle in ocfs2_dio_end_io_write() by freeing the allocation contexts (releasing EXTENT_ALLOC) before acquiring ORPHAN_DIR.
WARNING: possible circular locking dependency detected ------------------------------------------------------ is trying to acquire lock: ffff8881e78b33a0 (&ocfs2_sysfile_lock_key[INODE_ALLOC_SYSTEM_INODE]){+.+.}-{4:4}, at:
ocfs2_evict_inode+0x1539/0x43b0 fs/ocfs2/inode.c:1299
but task is already holding lock: ffff8881e78b4fa0 (&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]){+.+.}-{4:4}, at:
ocfs2_evict_inode+0xe97/0x43b0 fs/ocfs2/inode.c:1299
the existing dependency chain (in reverse order) is:
-> #2 (&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]){+.+.}-{4:4}:
inode_lock include/linux/fs.h:1029 [inline]
ocfs2_del_inode_from_orphan+0x12e/0x7a0 fs/ocfs2/namei.c:2728 ocfs2_dio_end_io+0xf9c/0x1370 fs/ocfs2/aops.c:2418 dio_complete+0x25b/0x790 fs/direct-io.c:281
-> #1 (&ocfs2_sysfile_lock_key[EXTENT_ALLOC_SYSTEM_INODE]){+.+.}-{4:4}:
inode_lock include/linux/fs.h:1029 [inline]
ocfs2_reserve_suballoc_bits+0x16d/0x4840 fs/ocfs2/suballoc.c:882 ocfs2_reserve_new_metadata_blocks+0x415/0x9a0 fs/ocfs2/suballoc.c:1078 ocfs2_mknod+0x10f3/0x2260 fs/ocfs2/namei.c:351
-> #0 (&ocfs2_sysfile_lock_key[INODE_ALLOC_SYSTEM_INODE]){+.+.}-{4:4}:
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 down_write+0x96/0x200 kernel/locking/rwsem.c:1625 inode_lock include/linux/fs.h:1029 [inline]
ocfs2_remove_inode fs/ocfs2/inode.c:733 [inline]
ocfs2_wipe_inode fs/ocfs2/inode.c:896 [inline]
ocfs2_delete_inode fs/ocfs2/inode.c:1157 [inline]
ocfs2_evict_inode+0x1539/0x43b0 fs/ocfs2/inode.c:1299
Chain exists of: &ocfs2_sysfile_lock_key[INODE_ALLOC_SYSTEM_INODE] -->
&ocfs2_sysfile_lock_key[EXTENT_ALLOC_SYSTEM_INODE] -->
&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]);
lock(&ocfs2_sysfile_lock_key[EXTENT_ALLOC_SYSTEM_INODE]);
lock(&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]);
lock(&ocfs2_sysfile_lock_key[INODE_ALLOC_SYSTEM_INODE]);
*** DEADLOCK ***
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Analysis
by VulDB Data Team • 09/04/2026
The Linux kernel's OCFS2 filesystem driver contained a critical concurrency flaw manifesting as a circular locking dependency among three internal system inodes: INODE_ALLOC_SYSTEM_INODE, EXTENT_ALLOC_SYSTEM_INODE, and ORPHAN_DIR_SYSTEM_INODE. This vulnerability was identified through lockdep warnings indicating that the kernel detected an unsafe locking scenario where tasks could deadlock due to inconsistent ordering of semaphore acquisitions across different execution paths within the filesystem codebase. The issue specifically resided in how direct I/O write completion operations interacted with inode eviction and deletion routines, creating a cycle that violated the strict hierarchical locking rules required for stable concurrent access to shared kernel resources.
The technical root cause lies in the divergent lock acquisition sequences employed by different OCFS2 functions during file system operations. The function ocfs2_mknod acquires locks in one order, specifically securing INODE_ALLOC followed by EXTENT_ALLOC when creating new nodes and allocating extents. Conversely, the direct I/O write completion handler, ocfs2_dio_end_io_write, operates under a different constraint where it must first acquire the EXTENT_ALLOC lock to handle unwritten extent conversions for performance optimization. However, during this process, if an inode needs to be removed from the orphan list, the code subsequently attempts to acquire the ORPHAN_DIR lock while still holding the EXTENT_ALLOC lock. This creates a partial ordering that conflicts with other paths in the kernel.
The deadlock cycle is completed by the ocfs2_wipe_inode function and its associated helpers like ocfs2_remove_inode. When an inode is being evicted or deleted, this routine attempts to acquire the ORPHAN_DIR lock first before proceeding to remove the inode from allocation structures which requires the INODE_ALLOC lock. This establishes a reverse dependency chain where one thread holds EXTENT_ALLOC and waits for ORPHAN_DIR, while another thread holds ORPHAN_DIR and waits for INODE_ALLOC, and potentially a third context or subsequent step in the same flow expects INODE_ALLOC to be held before re-acquiring other locks. The kernel's lock validator explicitly flagged this as a potential deadlock scenario where CPU0 might hold one lock and wait for another while CPU1 holds that second lock and waits for the first, resulting in an indefinite suspension of both processes.
From an operational impact perspective, this vulnerability allows for local denial-of-service conditions triggered by specific file system workloads involving direct I/O writes followed immediately by inode deletion or eviction events. An attacker with access to create files and perform high-volume direct write operations on OCFS2 mounted volumes could induce the deadlock state, effectively freezing kernel threads responsible for filesystem management until a manual reboot is performed. This impacts availability guarantees in enterprise environments relying on OCFS2 for clustered storage solutions where continuous uptime is critical. The vulnerability does not appear to allow privilege escalation or arbitrary code execution but severely degrades system stability under load.
The resolution involves restructuring the lock acquisition logic within ocfs2_dio_end_io_write to break the circular dependency chain. Specifically, the fix ensures that allocation contexts are freed and associated locks released before attempting to acquire the orphan directory lock during inode removal operations. By enforcing a consistent global ordering of these internal system file locks across all code paths, the kernel prevents the interleaving scenarios that lead to deadlock. This patch aligns with best practices for concurrent programming in operating systems by ensuring that resource acquisition follows a strict hierarchy or uses alternative synchronization mechanisms like trylock patterns where appropriate to avoid holding multiple heavy-weight locks simultaneously during complex state transitions.
This issue is categorized under CWE-833, Deadlock, which describes the condition resulting from two or more processes being blocked forever, waiting for each other. In terms of attack vector classification within MITRE ATT&CK, this falls under T1499 Endpoint Denial of Service, as it involves exhausting system resources to disrupt service availability rather than compromising confidentiality or integrity directly. Mitigation strategies include applying the upstream kernel patch that reorders lock acquisitions in the OCFS2 direct I/O path. System administrators should ensure their Linux kernels are updated to versions containing this fix and monitor for any signs of hung tasks related to filesystem operations on OCFS2 volumes, particularly during periods of high file creation and deletion activity combined with large direct write transfers.