The code in G1CollectedHeap::is_in() does not return whether the given pointer points into the committed heap.

bool G1CollectedHeap::is_in(const void* p) const {
  if (_hrm->reserved().contains(p)) {
    // Given that we know that p is in the reserved space,
    // heap_region_containing() should successfully
    // return the containing region.
    HeapRegion* hr = heap_region_containing(p);
    return hr->is_in(p);
  } else {
    return false;
  }
}

Two issues:
- heap_region_containing() returns a valid HeapRegion* for any region ever committed
- for uncommitted regions it returns NULL, i.e. crashing at the dereference

Is_in_exact() below seems to do what is expected and not slower.

There is no actual issue reported (i.e. crash) or misreporting.