Race condition

[arauhala]

There is a race condition in the mmap allocator memory management. Following sequence can happen:

1. Memory in address X is allocated. X is put into allocatedMemoryReferences
2. Memory in address X is released with 'close' request. X is removed from allocatedMemoryReferences
3. MemoryReference for address X has been garbage collected, and it is put into the 'queue'.
4. Memory in address X is reallocated. X is is put into allocatedMemoryReferences
5. Memory in address X is popped from 'queue', and because X is in allocatedMemoryReferences, it gets released second time.
6. Memory in address X is assumed to be allocated, and so it is used, which causes a segfault.