CVE-2025-40233

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

ocfs2: clear extent cache after moving/defragmenting extents

The extent map cache can become stale when extents are moved or

defragmented, causing subsequent operations to see outdated extent flags.

This triggers a BUG_ON in ocfs2_refcount_cal_cow_clusters().

The problem occurs when:

1. copy_file_range() creates a reflinked extent with OCFS2_EXT_REFCOUNTED

2. ioctl(FITRIM) triggers ocfs2_move_extents()

3. __ocfs2_move_extents_range() reads and caches the extent (flags=0x2)

4. ocfs2_move_extent()/ocfs2_defrag_extent() calls __ocfs2_move_extent()

which clears OCFS2_EXT_REFCOUNTED flag on disk (flags=0x0)

5. The extent map cache is not invalidated after the move

6. Later write() operations read stale cached flags (0x2) but disk has

updated flags (0x0), causing a mismatch

7. BUG_ON(!(rec->e_flags & OCFS2_EXT_REFCOUNTED)) triggers

Fix by clearing the extent map cache after each extent move/defrag

operation in __o

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References