iemejia opened a new pull request, #3854:
URL: https://github.com/apache/avro/pull/3854

   ## What is the purpose of the change
   
   `DataFileReaderBase::readDataBlock` bounds decompression across codecs: 
snappy and zstandard reject an over-large declared/frame size up front, while 
deflate and the zstd streaming path cap buffer growth and reject once the 
output would exceed the limit. Exceeding the limit throws an `avro::Exception`.
   
   When reading a data file, each block is decompressed according to the file's 
codec. A block with a very high compression ratio (or a malformed block) could 
expand to far more memory than its compressed size (a decompression bomb). This 
enforces a configurable maximum decompressed size while reading each block, 
mirroring the Java SDK's decompression limit (AVRO-4247). The limit defaults to 
200 MiB and can be overridden with the `AVRO_MAX_DECOMPRESS_LENGTH` environment 
variable.
   
   This is part of the umbrella issue AVRO-4283.
   
   ## Verifying this change
   
   This change added tests and can be verified as follows:
   
   - Added `test/DecompressionLimitTests.cc` (registered via 
`unittest(DecompressionLimitTests)`) covering deflate/snappy/zstandard 
over-limit rejection and within-limit decoding.
   - Run: `ctest -R DecompressionLimitTests`
   
   ## Documentation
   
   - Does this pull request introduce a new feature? (no — hardening/robustness)
   - If yes, how is the feature documented? (not applicable; the new 
`AVRO_MAX_DECOMPRESS_LENGTH` environment variable is documented in code 
comments)
   


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