CVE-2026-72211: ntfs: grow index root value before reparent header update

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

ntfs: grow index root value before reparent header update

ntfsirreparent() moves the resident index root entries into an index block and leaves a small root stub containing the child VCN. That root stub can be larger than the existing resident value. For example, an empty root with valuelength 48 has an index area of 32 bytes, while the large-index root stub needs indexlength and allocatedsize of 40 bytes.

The current code publishes the larger index.indexlength and index.allocatedsize before resizing the resident value. If the resize returns -ENOSPC, the recovery path can call ntfsinodeaddattrlist(), which looks attributes up again while the root header says allocatedsize 40 but the resident value still only provides 32 bytes of index area. Lookup-time $INDEXROOT validation then correctly rejects that transient layout as corrupt.

This reproduces as a generic/013 failure under qemu. In the failing run, the transient root had valuelen=48, indexsize=32, indexlength=40, and allocatedsize=40, and ntfsprogs-plus ntfsck reported "Corrupt index root in MFT record 1177".

When the root stub grows, resize the resident value before publishing the larger root header. If the resize fails, the old root remains valid for recovery lookups. Keep the existing header-before-resize ordering for shrink or same-size cases so the resident value never temporarily exposes an allocatedsize beyond its bounds.