CVE-2025-21722

Summary

CVE-2025-21722 is a vulnerability in the Linux kernel's nilfs2 filesystem that can lead to inconsistencies in buffer states when the filesystem is corrupted and falls back to read-only. This issue arises due to callbacks that handle page/folio write requests forcibly clearing the working state of buffers at unexpected times. Two specific instances of this issue have been identified: mark_buffer_dirty() sets a dirty buffer as read-only, and nilfs_btree_propagate() fails to propagate the dirty state to ancestor nodes. These vulnerabilities can result in buffer head use-after-free, leading to potential system instability or crashes. The patch series "nilfs2: protect busy buffer heads from being force-cleared" has been implemented to address these inconsistencies, ensuring that buffers are only cleared if they are not referenced.

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