linux-kernel - Re: New Security Features, Please Comment

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Date:	Fri, 5 Dec 2008 14:44:02 +1100
From:	Nick Andrew <nick@...k-andrew.net>
To:	Valdis.Kletnieks@...edu
Cc:	Geoffrey McRae <geoff@...idhost.com>,
	Peter Teoh <htmldeveloper@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: New Security Features, Please Comment

On Thu, Dec 04, 2008 at 10:35:27PM -0500, Valdis.Kletnieks@...edu wrote:
> You're also overlooking the fact that the malicious code could do something
> like this:
> 
> 	/* send the parent something that makes it *think* the request finished */
> 	printf("We're all done now\n");
> 	while (getpid()) msleep (1);

I think it's pretty basic that setgid/setuid needs to be done _before_
exec'ing untrusted code.

On the other hand, if a trusted process gets its uid changed _and_
expects this to happen then I suppose it can be secure. But if a
process's uid gets changed unexpectedly then nasty things already
pointed out by Alan and others can occur.

Nick.
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