CVE-2025-71295

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

fs/buffer: add alert in try_to_free_buffers() for folios without buffers

try_to_free_buffers() can be called on folios with no buffers attached

when filemap_release_folio() is invoked on a folio belonging to a mapping

with AS_RELEASE_ALWAYS set but no release_folio operation defined.

In such cases, folio_needs_release() returns true because of the

AS_RELEASE_ALWAYS flag, but the folio has no private buffer data. This

causes try_to_free_buffers() to call drop_buffers() on a folio with no

buffers, leading to a null pointer dereference.

Adding a check in try_to_free_buffers() to return early if the folio has no

buffers attached, with WARN_ON_ONCE() to alert about the misconfiguration.

This provides defensive hardening.