Re: How to develop a random number generation device

On Sat, 15 Sep 2007 04:43:40 +0100, Nobody wrote:

On Fri, 14 Sep 2007 17:33:28 +0000, Rich Grise wrote:

That doesn't address the issue, which was whether the OS can
prevent buffer overruns.

With a hardware MMU, and software that can catch the exception, yes.

That still doesn't address the question of how you decide that a write
operation has overrun its buffer; the details of where one buffer starts
and another ends are unknown to the OS.


But it knows what chunks of memory it has allocated to a particular
process. As long as it's in your own memory space, who cares if you
overwrite/overrun your own buffers?


You might be able to catch specific cases (e.g. overwriting a return
address), if you're willing to take a massive performance hit (i.e. a
context switch on all writes to the stack). Even then, that isn't the only
type of buffer overrun which can be exploited.

That's that sort of catchall "software that can catch the exception" part
of my answer. :-)

Cheers!
Rich

.

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