CVE-2025-40233

Summary

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The extent map cache can become stale when extents are moved or defragmented, causing subsequent operations to see outdated extent flags.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 __ocfs2_move_extents_range(). This ensures subsequent operations read fresh extent data from disk.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/93166bc53c0e3587058327a4121daea34b4fecd5
• https://git.kernel.org/stable/c/a7ee72286efba1d407c6f15a0528e43593fb7007
• https://git.kernel.org/stable/c/93b1ab422f1966b71561158e1aedce4ec100f357
• https://git.kernel.org/stable/c/e92af7737a94a729225d2a5d180eaaa77fe0bbc1
• https://git.kernel.org/stable/c/aa6a21409dd6221bb268b56bb410e031c632ff9a
• https://git.kernel.org/stable/c/bb69928ed578f881e68d26aaf1a8f6e7faab3b44
• https://git.kernel.org/stable/c/a21750df2f6169af6e039a3bb4893d6c9564e48d
• https://git.kernel.org/stable/c/78a63493f8e352296dbc7cb7b3f4973105e8679e

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