CVE-2024-41083 netfs: Fix netfs_page_mkwrite() to check folio->mapping is valid

In the Linux kernel, the following vulnerability has been resolved: netfs: Fix netfspagemkwrite to check folio-mapping is valid Fix netfspagemkwrite to check that folio-mapping is valid once it has taken the folio lock as filemappagemkwrite does. Without this, generic/247 occasionally oopses with...