Linux Kernel BTRFS: Missing new dentries log on parent fsync
CVE-2026-23465 Published on April 3, 2026
btrfs: log new dentries when logging parent dir of a conflicting inode
In the Linux kernel, the following vulnerability has been resolved:
btrfs: log new dentries when logging parent dir of a conflicting inode
If we log the parent directory of a conflicting inode, we are not logging
the new dentries of the directory, so when we finish we have the parent
directory's inode marked as logged but we did not log its new dentries.
As a consequence if the parent directory is explicitly fsynced later and
it does not have any new changes since we logged it, the fsync is a no-op
and after a power failure the new dentries are missing.
Example scenario:
$ mkdir foo
$ sync
$rmdir foo
$ mkdir dir1
$ mkdir dir2
# A file with the same name and parent as the directory we just deleted
# and was persisted in a past transaction. So the deleted directory's
# inode is a conflicting inode of this new file's inode.
$ touch foo
$ ln foo dir2/link
# The fsync on dir2 will log the parent directory (".") because the
# conflicting inode (deleted directory) does not exists anymore, but it
# it does not log its new dentries (dir1).
$ xfs_io -c "fsync" dir2
# This fsync on the parent directory is no-op, since the previous fsync
# logged it (but without logging its new dentries).
$ xfs_io -c "fsync" .
<power failure>
# After log replay dir1 is missing.
Fix this by ensuring we log new dir dentries whenever we log the parent
directory of a no longer existing conflicting inode.
A test case for fstests will follow soon.
Products Associated with CVE-2026-23465
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Affected Versions
Linux:- Version a3baaf0d786e22fc86295fda9c58ba0dee07599f and below 56e72c8b02d982be775d9df025357c152383ee84 is affected.
- Version a3baaf0d786e22fc86295fda9c58ba0dee07599f and below f556b1e09d054e31f464c0fd37280c2b5a393fee is affected.
- Version a3baaf0d786e22fc86295fda9c58ba0dee07599f and below 1cf30c73602c69d750c9345c47f2c0e9d0cfb578 is affected.
- Version a3baaf0d786e22fc86295fda9c58ba0dee07599f and below 6f5a51969b1deb79aefd2194b48fe7e78e72ff7e is affected.
- Version a3baaf0d786e22fc86295fda9c58ba0dee07599f and below 9573a365ff9ff45da9222d3fe63695ce562beb24 is affected.
- Version 5.1 is affected.
- Before 5.1 is unaffected.
- Version 6.6.130, <= 6.6.* is unaffected.
- Version 6.12.78, <= 6.12.* is unaffected.
- Version 6.18.20, <= 6.18.* is unaffected.
- Version 6.19.10, <= 6.19.* is unaffected.
- Version 7.0-rc5, <= * is unaffected.