CVE-2026-89841

Summary

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

f2fs: only redirty pinned folios in redirty_blocks

redirty_blocks() pins folios with read_cache_folio() and then walks the same range again with filemap_lock_folio() to redirty them and drop the references it took.

Commit 5951fee46bef ("f2fs: Use a folio in redirty_blocks()") changed the second pass to a do/while loop. If read_cache_folio() fails before anything is pinned, page_idx does not advance but the cleanup loop still runs once.

If readahead has already populated the failed folio in page cache, that extra iteration finds it and folio_put_refs(folio, 2) drops one reference too many. Later drop_caches or reclaim can then report "BUG: Bad page state".

Only redirty the range that was pinned successfully.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/445e4a1e6025ecd5312e9a95c1b234192c976ca1
• https://git.kernel.org/stable/c/89c65ec3c18903de763cf567c96ab3ef60e5f3b0
• https://git.kernel.org/stable/c/85171332742e741ccd6f401c69b6e0d698119e72

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