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Re: io_close proposal
From: |
Marcus Brinkmann |
Subject: |
Re: io_close proposal |
Date: |
Fri, 17 May 2002 02:28:35 +0200 |
User-agent: |
Mutt/1.3.28i |
On Thu, May 16, 2002 at 09:34:28AM -0700, Thomas Bushnell, BSG wrote:
> Marcus Brinkmann <address@hidden> writes:
>
> > Another idea: The actual number of extinct send rights (instead just a
> > boolean) could be helpful. If the server would get the exact number, and
> > it would be 1 (assuming the user does not transfer the send right),
> > he would know that the send right used to send the message was the only
> > one, and he could just go forward and destroy the port.
> > But I don't think this solution (if it is one) is very elegant.
>
> You mean the number of extant send rights. Mach will give you this
> information, but it is never reliable for this kind of purpose. It
> might be two when you call, and immediately one after that.
Well, the real problem, and the explanation why my idea won't work is this:
If the server sees 1 extant send right, he doesn't know if this is the
callers extant send right, or if the number of extant send rights has been
2 and the caller did:
io_close_request(port)
mach_port_deallocate(mach_task_self(), port);
So my idea doesn't work. If we would not have asynchronous messages,
this attack in the client probably wouldn't work (assuming proper guarantees
by the kernel). Well, I don't think it was obvious, so it is good to have
this idea proposed, discussed and dismissed.
This was my last trick, I don't have any better idea than sending the send
right in the message. So if nobody else has, we must concentrate on making
this solution work.
Thanks,
Marcus
--
`Rhubarb is no Egyptian god.' Debian http://www.debian.org address@hidden
Marcus Brinkmann GNU http://www.gnu.org address@hidden
address@hidden
http://www.marcus-brinkmann.de
- Re: io_close proposal, (continued)
- Re: io_close proposal, Roland McGrath, 2002/05/15
- Re: io_close proposal, Roland McGrath, 2002/05/15
- Re: io_close proposal, Marcus Brinkmann, 2002/05/16
- Re: io_close proposal, Thomas Bushnell, BSG, 2002/05/16
- Re: io_close proposal,
Marcus Brinkmann <=
- Re: io_close proposal, Thomas Bushnell, BSG, 2002/05/19
- Re: io_close proposal, Marcus Brinkmann, 2002/05/19
- Re: io_close proposal, Thomas Bushnell, BSG, 2002/05/19
Re: io_close proposal, Roland McGrath, 2002/05/16
- Re: io_close proposal, Marcus Brinkmann, 2002/05/16
- Re: io_close proposal, Marcus Brinkmann, 2002/05/16
- Re: io_close proposal, Roland McGrath, 2002/05/16
- Re: io_close proposal, Thomas Bushnell, BSG, 2002/05/16
- Re: io_close proposal, Roland McGrath, 2002/05/16
- Re: io_close proposal, Marcus Brinkmann, 2002/05/16