Suggested fix for JDK-4724038 (Add unmap method to MappedByteBuffer)

[Alan Bateman]

On 08/09/2015 09:58, Paul Sandoz wrote:
> HI Mike,
>
> This is fundamentally about *integrity* of the runtime. It follows there are security implications, but it’s still fundamentally an integrity issue and guarding an unsafe operation with a Security Manager is unfortunately an insufficient solution.
>
> Paul.
>
Right, and just to add that there has been many attempts over the years 
to find solutions to this issue. I think the closest was atomimcally 
remapping but that wasn't feasible on all platforms and also didn't free 
up the address space in a timely manner.

On the security manager suggestion then one of the concerns from a few 
years ago is that trusted code might unmap while untrusted code has a 
reference to the buffer.

There have been attempts using redirection too but there was always 
performance concerns. It also gets complicated with view buffers.

-Alan