AVRO-4323: [Java] Bound DataFileStream block size against available input before allocating the block buffer - #3919
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…nput When reading a data (container) file, DataFileStream validated the declared block size only against the Integer range before allocating the block buffer. For a malformed, corrupted, or truncated file the declared size can greatly exceed the bytes actually present, so the reader eagerly allocated a large buffer before reading any block byte. Reject a declared block size that exceeds the number of bytes remaining in the input when that count is known (byte-array- or known-length-stream-backed decoders), so reading a malformed file fails fast with a clear IOException. The check is skipped when the remaining count is unknown (-1).
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What changes were proposed in this pull request?
When reading an Avro data (container) file,
DataFileStreamreads each block's declared size as alongand validated it only against theIntegerrange before allocating the blockbyte[]buffer (inDataFileStream.DataBlock). For a malformed, corrupted, or truncated file, the declared block size can be much larger than the number of bytes actually present, so the reader eagerly allocated a very large buffer on the firsthasNext()/next()call before any block byte had been read.This adds a check: when the number of bytes remaining in the input is known (byte-array- or known-length-stream-backed decoders), a declared block size larger than the bytes remaining is rejected with a clear
IOExceptionbefore allocating. The check is skipped when the remaining count is unknown (-1), so non-seekable streams are unaffected.How was this patch tested?
TestDataFileReader:oversizedBlockSizeIsRejectedBeforeAllocation— a crafted file whose block header declares a size nearInteger.MAX_VALUEwith no block bytes now fails fast instead of attempting a large allocation.validFileWithSingleRecordStillReads— negative control confirming a valid file still reads.avromodule test suite passes.JIRA