RFR: 8306461: ObjectInputStream::readObject() should handle negative array sizes without throwing NegativeArraySizeExceptions

[Volker Simonis]

This issue was reported by: Yakov Shafranovich ([yakovsh at amazon.com](mailto:yakovsh at amazon.com))

Currently, `ObjectInputStream::readObject()` doesn't explicitly checks for a negative array length in the deserialization stream. Instead it calls `j.l.r.Array::newInstance(..)` with the negative length which results in a `NegativeArraySizeException`. NegativeArraySizeException is an unchecked exception which is neither declared in the signature of `ObjectInputStream::readObject()` nor mentioned in its API specification. It is therefore not obvious for users of `ObjectInputStream::readObject()` that they may have to handle `NegativeArraySizeException`s. It would therefor be better if a negative array length in the deserialization stream would be automatically wrapped in an `InvalidClassException` which is a checked exception (derived from `IOException` via `ObjectStreamException`) and declared in the signature of `ObjectInputStream::readObject()`.

If we do the negative array length check in `ObjectInputStream::readObject()` before filtering, this will then also fix `ObjectInputFilter.FilterInfo::arrayLength()` which is defined as:

Returns:
the non-negative number of array elements when deserializing an array of the class, otherwise -1

but currently returns a negative value if the array length is negative.

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Commit messages:
 - 8306461: ObjectInputStream::readObject() should handle negative array sizes without throwing NegativeArraySizeExceptions

Changes: https://git.openjdk.org/jdk/pull/13540/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13540&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306461
  Stats: 115 lines in 2 files changed: 114 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13540.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13540/head:pull/13540

PR: https://git.openjdk.org/jdk/pull/13540