Executive brief
This is not a security vulnerability but a feature removal. The Linux kernel's EROFS filesystem removed its fscache backend after it was deprecated for two years. The fscache feature was used for lazy loading of filesystem images but introduced unwanted hard dependencies and complexity. Removal of this deprecated code reduces kernel maintenance burden and eliminates concerns about underlying implementation issues.
Technical details
This is a code cleanup patch removing the fscache backend from EROFS (Enhanced Read-Only File System). The fscache subsystem was originally introduced to enable lazy pulling of filesystem images but created an unexpected hard dependency on the netfs kernel subsystem for a local filesystem. The removal eliminates approximately 847 lines of code and related configuration options. The commit removes fscache-specific functions, mount options (fsid, domain_id-related fscache features), and dependencies while preserving file-backed mounts and fanotify pre-content hooks as alternative mechanisms. Existing applications like Nydus plan to migrate to fanotify pre-content hooks.
Affected products
- Linux Linux kernel 7.2 and later
Timeline
- 2026-06-22: disclosed
- 2026-09-04: patched: Merged into Linux 7.2