CVE-2026-89841

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.