When the unreadable directory has an ATTRIBUTE_LIST attribute and an
INDEX_ALLOCATION attribute occupying split over several extents, the first
of which defines a single cluster, the first INDEX_ALLOCATION extent has
lowest_vcn=0 and highest_vcn=0, and the second one has lowest_vcn=1.
This unusual case, which can be created by the combination of a small
volume and near-full MFT records, triggers some special-case behavior in
ntfs_mapping_pairs_decompress_i(). That behavior is incorrect if the
attribute's first extent only contains a single cluster, since in that case
highest_vcn=0 as well.
This configuration has been tested on Windows and it *is* able to
successfully read the directory. This supports the hypothesis that the
volume is valid and NTFS-3g has a bug on the read side.
This bug could, in theory, occur with any non-resident attribute, not just
INDEX_ALLOCATION attributes.
(Contributed by Eric Biggers)
