Developer Details Apple Filesystem Bug

A bug in Apple's fsck_hfs tool could cause data loss when repairing older HFS+ file systems, a developer has found.

A developer has documented a bug in fsck_hfs, Apple's command-line utility for checking and repairing the HFS+ file system. HFS+ is an older file system, largely superseded by APFS on modern Apple devices. The bug relates to how the tool handles the catalog B-tree, a core data structure that organizes files and folders. Under certain conditions, fsck_hfs can misinterpret the tree's structure, causing it to incorrectly identify parts of the file system as corrupted. When attempting a repair, this misinterpretation can lead the tool to overwrite valid data, resulting in permanent data loss.

While HFS+ is a legacy file system, it is still used in various scenarios, including on older Macs, external drives formatted for compatibility, and within disk images. This bug poses a risk for any user or IT administrator relying on fsck_hfs to recover data from a damaged HFS+ volume. The discovery serves as a reminder that even long-standing, mature system utilities can contain critical flaws. It underscores the importance of understanding the potential risks of data recovery tools, especially when dealing with older technologies that may receive less frequent scrutiny.