Linux Kernel EUVD-2026-27663

HFS+ (Hierarchical File System Plus) is Apple's legacy filesystem format, supported in the Linux kernel via the hfsplus driver. Internally, hfsplus maintains a set of 'special inodes' - fixed-purpose metadata files such as the catalog B-tree, extents overflow file, allocation bitmap, and attributes file - that are represented as VFS inodes but were not assigned any of the standard POSIX mode type bits (S_IFDIR, S_IFLNK, S_IFREG, etc.). Kernel commit af153bb63a33 ('vfs: catch invalid modes in may_open()') added an enforcement gate in the VFS may_open() path that rejects any inode whose mode does not carry one of those canonical type flags. Once that VFS hardening landed, accessing a mounted HFS+ volume would cause these untyped special inodes to fail the check, triggering a kernel-level error path (BUG/WARN/OOPS or panic). The fix reassigns these special inodes the S_IFREG type flag to satisfy the VFS constraint without changing their actual behaviour. CPE data identifies the affected platform as cpe:2.3:a:linux:linux and patched stable branches span 5.10.x through 7.0. No CWE is assigned, but the root cause class is improper inode type initialisation - a variant of incorrect resource characterisation.