iemejia opened a new pull request, #3928:
URL: https://github.com/apache/avro/pull/3928
## What is the purpose of the change
Java SDK implementation of AVRO-4302 (parent). Recursive schemas (e.g. a
linked list or tree) let a small, hostile payload drive arbitrarily deep
nesting during binary decoding, exhausting the call stack with a
`StackOverflowError` before any allocation limit is reached.
This adds a configurable maximum decode nesting depth, enforced by counting
structural descents into records, arrays, maps and unions and rejecting input
that nests deeper than the limit with a bounded `SystemLimitException`
instead
of a `StackOverflowError`. The default is 100 (matching Protocol Buffers) and
is configurable via the `org.apache.avro.limits.decode.maxDepth` system
property. The depth is tracked in the existing per-thread decode scope, so a
reader reused concurrently cannot corrupt another thread's counter and no
reader method signatures change. Both reader paths are guarded: the classic
`GenericDatumReader` (and its Specific/Reflect subclasses) via
`readWithoutConversion`, and the `FastReaderBuilder` record/map/union/array
readers.
## Verifying this change
This change added tests and can be verified as follows:
- Added `TestDecodeRecursionDepth`: a ~100k-deep recursive linked-list
payload
is rejected with a bounded `SystemLimitException` (not a
`StackOverflowError`)
on both the classic and fast reader paths, while a moderately nested value
within the limit still decodes.
- Added unit tests in `TestSystemLimitException` for the depth counter, the
custom-limit property, and the outer-scope reset.
- Verified across the module's three Surefire runs (default, custom-coders,
without-fast-reader).
## Documentation
- Does this pull request introduce a new feature? (no — DoS hardening)
- If yes, how is the feature documented? (JavaDocs — the new limit is
documented
on `SystemLimitException` alongside the existing collection/decompress
limits)
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