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

From: Alan Cox
Date: Tue Aug 08 2006 - 07:51:08 EST

Ar Llu, 2006-08-07 am 22:52 +0000, ysgrifennodd David Wagner:
> 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

No its revoked. Just like a tty hangup

> 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.

Of course it doesn't. The BSD folk who added revoke were security people
not idiots.


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