- Add ensure_len(data, offset, needed) helper to chunked_read.rs,
data_read.rs, and local_heap.rs (matching the existing btree_v1.rs/
object_header.rs convention) and use it at every plain-arithmetic
offset+size bounds check found in these files, closing usize-overflow
panics reachable from crafted near-usize::MAX offsets/addresses.
- collect_chunk_info: add a depth-limited internal wrapper
(collect_chunk_info_inner, MAX_CHUNK_BTREE_DEPTH=64) to reject a
crafted self-referencing/cyclic B-tree v1 chunk index instead of
recursing unboundedly (stack-overflow DoS).
- read_compound_fields: validate byte_offset+field_size against the
compound's declared element size before slicing, instead of an
unguarded out-of-bounds panic on a crafted member offset.
- read_chunked_data/_cached/_sweep/_indexed: guard `ndims - 1` against
underflow for a degenerate zero-dimension chunked layout.
- copy_chunk_to_output: rewrite all offset/stride arithmetic (both the
1-D fast path and the general N-D path) to use checked_add/checked_mul,
skipping an out-of-range row/chunk instead of panicking on overflow.
Add a new cargo-fuzz target, fuzz_dataset_read, that walks every dataset
in a parsed file via the clawhdf5 facade and exercises the contiguous/
chunked/compact raw-data read paths that the existing fuzz_full_file
target doesn't reach. Seeded with the chunked/VDS/compound-relevant test
fixtures plus two crash regressions found during this pass (the
copy_chunk_to_output overflow and the ndims-1 underflow, both fixed
above — this target found real bugs within the first couple of runs).
Not wired into CI (nightly-only, multi-minute runs); documented in
fuzz/README.md as a manual/scheduled check instead. Also fixed the
README's stale rustyhdf5-format naming while touching this file.
Added regression tests for every fix (near-usize::MAX offsets, the
self-referencing B-tree case, the compound byte_offset overrun, the
zero-dim layout, and both copy_chunk_to_output overflow paths) so these
are caught by `cargo test`, not just the fuzz corpus.
Omar Sobh