CVE-2025-22000: Missing Release of Memory after Effective Lifetime

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

mm/huge_memory: drop beyond-EOF folios with the right number of refs

When an after-split folio is large and needs to be dropped due to EOF, folio_put_refs(folio, folio_nr_pages(folio)) should be used to drop all page cache refs. Otherwise, the folio will not be freed, causing memory leak.

This leak would happen on a filesystem with blocksize > page_size and a truncate is performed, where the blocksize makes folios split to >0 order ones, causing truncated folios not being freed.