Possible memory leak in java.nio.DirectByteBuffer and java.nio.ByteBuffer.allocateDirect if OutOfMemoryError is thrown

[John Platts]

Here is the code for the java.nio.DirectByteBuffer(int) constructor, which is contained in the Direct-X-Buffer.java.template file, starting at line 117:
Direct$Type$Buffer$RW$(int cap) {                   // package-private
#if[rw]
        super(-1, 0, cap, cap);
        boolean pa = VM.isDirectMemoryPageAligned();
        int ps = Bits.pageSize();
        long size = Math.max(1L, (long)cap + (pa ? ps : 0));
        Bits.reserveMemory(size, cap);

        long base = 0;
        try {
            base = unsafe.allocateMemory(size);
        } catch (OutOfMemoryError x) {
            Bits.unreserveMemory(size, cap);
            throw x;
        }
        unsafe.setMemory(base, size, (byte) 0);
        if (pa && (base % ps != 0)) {
            // Round up to page boundary
            address = base + ps - (base & (ps - 1));
        } else {
            address = base;
        }
        cleaner = Cleaner.create(this, new Deallocator(base, size, cap));
        att = null;
#else[rw]
        super(cap);
        this.isReadOnly = true;
#end[rw]
    }

A memory leak of the memory allocated by the base = unsafe.allocateMemory(size) statement in line 127 of the Direct-X-Buffer.java.template file can occur if an OutOfMemoryError is thrown by the cleaner = Cleaner.create(this, new Deallocator(base, size, cap)) statement in line 139 of the Direct-X-Buffer.java.template file.

Here is one way to fix the issue:
Bits.reserveMemory(size, cap);

long base = 0;
try {
    base = unsafe.allocateMemory(size);
    unsafe.setMemory(base, size, (byte)0);
    if (pa && (base % ps != 0)) {
        // Round up to page boundary
        address = base + ps - (base & (ps - 1));
    } else {
        address = base;
    }
    cleaner = Cleaner.create(this, new Deallocator(base, size, cap));
} catch(OutOfMemoryError x) {
    Bits.unreserveMemory(size, cap);
    if(base != 0 && cleaner == null) {
        // If the memory block has been allocated, but cleaner has not yet been allocated, free the allocated
        // memory block before rethrowing the OutOfMemoryError.
        address = 0;
        unsafe.freeMemory(base);
    }
    throw x;
}
att = null;