linux-kernel - Re: Syslets, signals, and security

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Message-ID: <p73vee3a14x.fsf@bingen.suse.de>
Date:	04 Jun 2007 22:57:34 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Jeff Dike <jdike@...toit.com>
Cc:	Zach Brown <zach.brown@...cle.com>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Syslets, signals, and security

Jeff Dike <jdike@...toit.com> writes:

> How about splitting the credentials out of the task_struct and making
> them sharable ala ->mm et al?  You change uid there and it changes for
> everyone.  It will make fork slightly more expensive though.

Strictly that's required by POSIX anyways. But it's a real mess.

The problem is that you would need to reference count/lock them in every
syscall or ioctl or similar. Otherwise another thread
could change them in the middle of a syscall which wouldn't be
good. Doing this full reference counting would be probably somewhat
expensive with more locked cycles and also a lot of work to implement.
You would need to audit large parts of the source tree.

I don't think it's a good idea.

-Andi
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