linux-kernel - Re: [RFC/PATCH] revoke/frevoke system calls V2

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Date:	Mon, 7 Aug 2006 18:56:42 -0400
From:	Daniel Jacobowitz <dan@...ian.org>
To:	David Wagner <daw-usenet@...erner.cs.berkeley.edu>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [RFC/PATCH] revoke/frevoke system calls V2

On Mon, Aug 07, 2006 at 10:52:59PM +0000, David Wagner wrote:
> I'm still trying to understand the semantics of this proposed
> frevoke() implementation.  Can an attacker use this to forcibly
> close some other processes' file descriptor?  Suppose the target
> process has fd 0 open and the attacker revokes the file corresponding
> to fd 0; what is the state of fd 0 in the target process?  Is it
> closed?  If the target process then open()s another file, does it
> get bound to fd 0?  (Recall that open() always binds to the lowest
> unused fd.)  If the answers are "yes", then the security consequences
> seem very scary.

No, that's already been answered at least once.  The file remains open,
but returns EBADF on various operations.

-- 
Daniel Jacobowitz
CodeSourcery
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