Re: reading the same entropy twice

From: Matt Mackall
Date: Wed Feb 23 2005 - 01:41:15 EST


On Tue, Feb 22, 2005 at 04:55:39PM -0500, Bob O'Neill wrote:
> Hello.
>
> I have noticed that it is possible on an SMP box for two processes to
> simultaneously read the same entropy out of /dev/urandom. This
> doesn't seem right to me. I was using the entropy value to generate a
> random number to use as a session ID, so occasionally there would be a
> collision on session IDs, causing a login failure as session IDs are
> required to be unique. This issue does not appear to be related to
> entropy depletion.
>
> Could you provide me with some insight into why this is the case, if
> it is intentional? It seems like it could be addressed with a
> spinlock.

This should be fixed in current kernels.

--
Mathematics is the supreme nostalgia of our time.
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