iemejia opened a new pull request, #3853:
URL: https://github.com/apache/avro/pull/3853

   ## What is the purpose of the change
   
   The deflate and lzma codecs cap buffer growth and reject once the output 
would exceed the limit; snappy rejects an over-large declared length up front. 
Exceeding the limit fails decoding with a descriptive error.
   
   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 `tests/test_avro_4284.c` (registered in `tests/CMakeLists.txt`) 
exercising deflate, snappy and lzma over-limit rejection.
   - Run: `ctest -R test_avro_4284` (also passes under the valgrind memcheck 
variant)
   
   ## 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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