[foreign-memaccess+abi] RFR: 8294309: Downcall and Upcall unboxing code should reject heap segments

[Jorn Vernee]

On Tue, 4 Oct 2022 12:04:51 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Recently I noticed that we don't check for heap segments anymore when unboxing memory segments to be passed to native code as addresses. This allows someone to pass a heap segment, which will be unboxed simply by calling `MemorySegment::address` which for heap segments returns the byte offset into the array. This is of course not a valid pointer.
>> 
>> This patch changes the unboxing logic to reject heap segments with an `IllegalArgumentException`.
>
> src/java.base/share/classes/jdk/internal/foreign/abi/SharedUtils.java line 265:
> 
>> 263: 
>> 264:     static long unboxSegment(MemorySegment segment) {
>> 265:         if (segment instanceof HeapMemorySegmentImpl) {
> 
> there's MemorySegment.isNative, which maybe is better?

Yeah, that works. It also includes mapped segments

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PR: https://git.openjdk.org/panama-foreign/pull/737