CVE-2026-72199: ntfs: validate resident index root values on lookup

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

ntfs: validate resident index root values on lookup

Resident $INDEXROOT values carry index header fields that callers consume after lookup. Some callers already validate parts of the layout before walking entries, but those checks are scattered and do not cover all root header invariants, such as entriesoffset alignment and lower bound, indexlength, and allocatedsize consistency.

The resident root resize paths now keep these header fields consistent while the value size changes: ntfsirtruncate() lowers index.allocatedsize before shrinking the resident value, and ntfsirreparent() grows the resident value before publishing a larger root header. Lookup-time validation can therefore cover these invariants without tripping over the driver's own resize paths.

Add $INDEXROOT to the minimum resident value size table and validate the resident index header fields before returning the attribute from lookup. Require 8-byte aligned index header fields, a sane entriesoffset, an indexlength within allocatedsize, allocatedsize within the resident value, and enough entry space for at least an index entry header.

The shared validator already rejects non-resident records for resident-only attribute types, including $INDEXROOT.