- if (gmem_flags & GUEST_MEMFD_FLAG_NO_DIRECT_MAP) {+ if (!ops->accessible && (gmem_flags & GUEST_MEMFD_FLAG_NO_DIRECT_MAP)) { r = guest_memfd_folio_private(folio); if (r) goto out_err; @@ -107,6 +109,82 @@ struct folio *guest_memfd_grab_folio(struct file *file, pgoff_t index, u32 flags } EXPORT_SYMBOL_GPL(guest_memfd_grab_folio);+int guest_memfd_make_inaccessible(struct file *file, struct folio *folio)+{ + unsigned long gmem_flags = (unsigned long)file->private_data; + unsigned long i; + int r; + + unmap_mapping_folio(folio); + + /** + * We can't use the refcount. It might be elevated due to + * guest/vcpu trying to access same folio as another vcpu + * or because userspace is trying to access folio for same reason
As discussed, that's insufficient. We really have to drive the refcount to 1 -- the single reference we expect.
What is the exact problem you are running into here? Who can just grab a reference and maybe do nasty things with it?
-- Cheers, David / dhildenb
