CVE-2025-71069
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2026-01-13

Last updated on: 2026-01-19

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: f2fs: invalidate dentry cache on failed whiteout creation F2FS can mount filesystems with corrupted directory depth values that get runtime-clamped to MAX_DIR_HASH_DEPTH. When RENAME_WHITEOUT operations are performed on such directories, f2fs_rename performs directory modifications (updating target entry and deleting source entry) before attempting to add the whiteout entry via f2fs_add_link. If f2fs_add_link fails due to the corrupted directory structure, the function returns an error to VFS, but the partial directory modifications have already been committed to disk. VFS assumes the entire rename operation failed and does not update the dentry cache, leaving stale mappings. In the error path, VFS does not call d_move() to update the dentry cache. This results in new_dentry still pointing to the old inode (new_inode) which has already had its i_nlink decremented to zero. The stale cache causes subsequent operations to incorrectly reference the freed inode. This causes subsequent operations to use cached dentry information that no longer matches the on-disk state. When a second rename targets the same entry, VFS attempts to decrement i_nlink on the stale inode, which may already have i_nlink=0, triggering a WARNING in drop_nlink(). Example sequence: 1. First rename (RENAME_WHITEOUT): file2 → file1 - f2fs updates file1 entry on disk (points to inode 8) - f2fs deletes file2 entry on disk - f2fs_add_link(whiteout) fails (corrupted directory) - Returns error to VFS - VFS does not call d_move() due to error - VFS cache still has: file1 → inode 7 (stale!) - inode 7 has i_nlink=0 (already decremented) 2. Second rename: file3 → file1 - VFS uses stale cache: file1 → inode 7 - Tries to drop_nlink on inode 7 (i_nlink already 0) - WARNING in drop_nlink() Fix this by explicitly invalidating old_dentry and new_dentry when f2fs_add_link fails during whiteout creation. This forces VFS to refresh from disk on subsequent operations, ensuring cache consistency even when the rename partially succeeds. Reproducer: 1. Mount F2FS image with corrupted i_current_depth 2. renameat2(file2, file1, RENAME_WHITEOUT) 3. renameat2(file3, file1, 0) 4. System triggers WARNING in drop_nlink()
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Meta Information
Published
2026-01-13
Last Modified
2026-01-19
Generated
2026-05-06
AI Q&A
2026-01-14
EPSS Evaluated
2026-05-05
NVD
CVE-2025-71069
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability occurs in the Linux kernel's F2FS filesystem when it handles rename operations involving whiteouts on directories with corrupted directory depth values. During a RENAME_WHITEOUT operation, partial directory modifications are committed to disk before the system attempts to add a whiteout entry. If adding the whiteout entry fails due to corruption, the system returns an error but does not update the dentry cache, leaving stale cache entries that reference freed inodes. This stale cache causes subsequent operations to incorrectly reference invalid inodes, potentially triggering warnings or errors in the kernel.


How can this vulnerability impact me? :

This vulnerability can cause the filesystem's directory cache to become inconsistent with the on-disk state, leading to stale cache entries that reference freed inodes. This inconsistency can trigger kernel warnings (such as WARNING in drop_nlink()), potentially causing system instability or unexpected behavior during file rename operations on corrupted F2FS filesystems.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by monitoring system logs for WARNING messages related to drop_nlink(), which occur when the stale dentry cache causes inode link count inconsistencies. Specifically, look for WARNINGs triggered during rename operations on F2FS filesystems. A reproducer sequence involves mounting an F2FS image with corrupted directory depth and performing renameat2 operations that trigger the issue. Commands to check logs include: `dmesg | grep drop_nlink` or `journalctl -k | grep drop_nlink`. Additionally, monitoring for filesystem corruption or anomalies in rename operations on F2FS may help detect the issue.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation steps include updating the Linux kernel to a version that contains the fix for this vulnerability, which explicitly invalidates the dentry cache on failed whiteout creation to prevent stale cache usage. Until the update is applied, avoid performing RENAME_WHITEOUT operations on F2FS filesystems with corrupted directory depth values, as these trigger the issue. Also, monitor system logs for warnings related to drop_nlink() to detect potential exploitation or occurrence.


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