DecimalVector.setBigEndian writes oversized value before validating length

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
72/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
java
Domain
data

Research direction

Start at DecimalVector.setBigEndian and Decimal256Vector.setBigEndian, then compare setBigEndianSafe; inspect how fixed-width slots and length validation are handled. Reproduce an oversized input for a nonzero slot and add coverage showing adjacent memory is unchanged while invalid lengths still throw. Done means all three entry points reject oversized values before writing.

Written by the indexing model from the issue text.

Description

DecimalVector.setBigEndian(int, byte[]) and Decimal256Vector.setBigEndian(int, byte[]) validate the input length only after copying the bytes. On a little-endian platform the method byte-swaps the value into the fixed 16/32-byte slot with a loop of unchecked MemoryUtil.putByte writes:

for (int byteIdx = 0; byteIdx < length; ++byteIdx) {
  MemoryUtil.putByte(outAddress + byteIdx, value[length - 1 - byteIdx]);
}
...
throw new IllegalArgumentException("Invalid decimal value length. Valid length in [1 - 16], got " + length);

If value.length exceeds the type width, the loop writes past the slot into adjacent off-heap memory before the IllegalArgumentException is thrown. MemoryUtil.putByte does no bounds checking, so this corrupts memory in the default configuration. setBigEndianSafe(int, long, ArrowBuf, int) performs the same write with no length check at all.

Reproducer: write a value into slot 1, then call setBigEndian(0, new byte[24]) on a DecimalVector; slot 1 is left corrupted (the write spills 8 bytes into it) even though the call throws.

Dominant language
Java
Stars
95
Forks
154
Avg merge
2d 16h
Merged PRs (30d)
9

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