iemejia commented on code in PR #3928:
URL: https://github.com/apache/avro/pull/3928#discussion_r3737488507
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lang/java/avro/src/main/java/org/apache/avro/io/FastReaderBuilder.java:
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@@ -478,48 +483,57 @@ private FieldReader createArrayReader(Schema
readerSchema, Container action) thr
boolean zeroByteElements =
GenericDatumReader.isZeroByteSchema(elementType);
return reusingReader((reuse, decoder) -> {
- // Open a decode scope so the zero-byte element allocation cap is
cumulative
- // across every block of this array even when the fast reader is used
- // standalone (i.e. without GenericDatumReader.read opening the outer
datum
- // scope); otherwise a huge array split into many small blocks would
bypass
- // the cap. The scope nests: when a datum scope is already open this
simply
- // accumulates into it, and only the outermost scope resets the running
- // total (see SystemLimitException). The try/finally guarantees the
scope is
- // always closed so ThreadLocal state cannot leak into later decodes on
the
- // same thread.
- SystemLimitException.beginCollectionAllocationScope();
+ // Descending into an array grows the decode call stack; bound the
nesting
+ // depth first so a recursive schema cannot overflow the stack. Kept
outside
+ // the collection-allocation scope below so that when the depth check
throws
+ // (before incrementing) no unbalanced decrement occurs.
+ SystemLimitException.incrementDecodeDepth();
Review Comment:
Good catch, that ordering was wrong. Fixed in the latest commit:
`createArrayReader` now opens the collection-allocation scope first (so it
resets any stale depth at the outermost datum boundary), then increments the
decode depth to count the array's level, with both the depth decrement and the
scope end in `finally` blocks (a throw from the depth check still closes the
scope). Added a regression test that drives the standalone fast-reader
top-level-array path with a deeply nested element.
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