CVE-2025-68778
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2026-01-13

Last updated on: 2026-01-14

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: btrfs: don't log conflicting inode if it's a dir moved in the current transaction We can't log a conflicting inode if it's a directory and it was moved from one parent directory to another parent directory in the current transaction, as this can result an attempt to have a directory with two hard links during log replay, one for the old parent directory and another for the new parent directory. The following scenario triggers that issue: 1) We have directories "dir1" and "dir2" created in a past transaction. Directory "dir1" has inode A as its parent directory; 2) We move "dir1" to some other directory; 3) We create a file with the name "dir1" in directory inode A; 4) We fsync the new file. This results in logging the inode of the new file and the inode for the directory "dir1" that was previously moved in the current transaction. So the log tree has the INODE_REF item for the new location of "dir1"; 5) We move the new file to some other directory. This results in updating the log tree to included the new INODE_REF for the new location of the file and removes the INODE_REF for the old location. This happens during the rename when we call btrfs_log_new_name(); 6) We fsync the file, and that persists the log tree changes done in the previous step (btrfs_log_new_name() only updates the log tree in memory); 7) We have a power failure; 8) Next time the fs is mounted, log replay happens and when processing the inode for directory "dir1" we find a new INODE_REF and add that link, but we don't remove the old link of the inode since we have not logged the old parent directory of the directory inode "dir1". As a result after log replay finishes when we trigger writeback of the subvolume tree's extent buffers, the tree check will detect that we have a directory a hard link count of 2 and we get a mount failure. The errors and stack traces reported in dmesg/syslog are like this: [ 3845.729764] BTRFS info (device dm-0): start tree-log replay [ 3845.730304] page: refcount:3 mapcount:0 mapping:000000005c8a3027 index:0x1d00 pfn:0x11510c [ 3845.731236] memcg:ffff9264c02f4e00 [ 3845.731751] aops:btree_aops [btrfs] ino:1 [ 3845.732300] flags: 0x17fffc00000400a(uptodate|private|writeback|node=0|zone=2|lastcpupid=0x1ffff) [ 3845.733346] raw: 017fffc00000400a 0000000000000000 dead000000000122 ffff9264d978aea8 [ 3845.734265] raw: 0000000000001d00 ffff92650e6d4738 00000003ffffffff ffff9264c02f4e00 [ 3845.735305] page dumped because: eb page dump [ 3845.735981] BTRFS critical (device dm-0): corrupt leaf: root=5 block=30408704 slot=6 ino=257, invalid nlink: has 2 expect no more than 1 for dir [ 3845.737786] BTRFS info (device dm-0): leaf 30408704 gen 10 total ptrs 17 free space 14881 owner 5 [ 3845.737789] BTRFS info (device dm-0): refs 4 lock_owner 0 current 30701 [ 3845.737792] item 0 key (256 INODE_ITEM 0) itemoff 16123 itemsize 160 [ 3845.737794] inode generation 3 transid 9 size 16 nbytes 16384 [ 3845.737795] block group 0 mode 40755 links 1 uid 0 gid 0 [ 3845.737797] rdev 0 sequence 2 flags 0x0 [ 3845.737798] atime 1764259517.0 [ 3845.737800] ctime 1764259517.572889464 [ 3845.737801] mtime 1764259517.572889464 [ 3845.737802] otime 1764259517.0 [ 3845.737803] item 1 key (256 INODE_REF 256) itemoff 16111 itemsize 12 [ 3845.737805] index 0 name_len 2 [ 3845.737807] item 2 key (256 DIR_ITEM 2363071922) itemoff 16077 itemsize 34 [ 3845.737808] location key (257 1 0) type 2 [ 3845.737810] transid 9 data_len 0 name_len 4 [ 3845.737811] item 3 key (256 DIR_ITEM 2676584006) itemoff 16043 itemsize 34 [ 3845.737813] location key (258 1 0) type 2 [ 3845.737814] transid 9 data_len 0 name_len 4 [ 3845.737815] item 4 key (256 DIR_INDEX 2) itemoff 16009 itemsize 34 [ 3845.737816] location key (257 1 0) type 2 [ ---truncated---
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Meta Information
Published
2026-01-13
Last Modified
2026-01-14
Generated
2026-05-07
AI Q&A
2026-01-14
EPSS Evaluated
2026-05-05
NVD
CVE-2025-68778
EUVD
EUVD-2026-2322
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 in the Linux kernel's btrfs filesystem occurs when a directory is moved from one parent directory to another within the same transaction, and the system attempts to log conflicting inode information. Specifically, the issue arises because the system logs the inode of the moved directory's new location but fails to log the old parent directory. During log replay after a power failure, this causes the directory to appear as if it has two hard links (one from the old parent and one from the new), which is invalid. This results in a mount failure due to the filesystem detecting an inode with an invalid hard link count of 2 for a directory, which should have only one.


How can this vulnerability impact me? :

This vulnerability can cause the btrfs filesystem to fail to mount after a power failure or crash because the filesystem's integrity checks detect an invalid hard link count on a directory inode. This mount failure can lead to system downtime, potential data inaccessibility, and disruption of services relying on the affected filesystem until the issue is resolved or repaired.


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

You can detect this vulnerability by checking the system logs (dmesg or syslog) for BTRFS errors related to directory inode hard link counts and mount failures. Specifically, look for messages like 'BTRFS critical: corrupt leaf' and 'invalid nlink: has 2 expect no more than 1 for dir'. Commands to check include: `dmesg | grep BTRFS`, `journalctl -k | grep BTRFS`, or `grep BTRFS /var/log/syslog`.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation steps include updating the Linux kernel to a version where this BTRFS vulnerability is fixed. Avoid performing operations that move directories and create files with the same name in the same transaction until the fix is applied. Also, ensure regular backups to prevent data loss in case of mount failures due to this issue.


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