linux-kernel - Re: [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF

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Message-ID: <20120112232735.5fa251e3@pyramind.ukuu.org.uk>
Date:	Thu, 12 Jan 2012 23:27:35 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Jamie Lokier <jamie@...reable.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org,
	keescook@...omium.org, john.johansen@...onical.com,
	serge.hallyn@...onical.com, coreyb@...ux.vnet.ibm.com,
	pmoore@...hat.com, eparis@...hat.com, djm@...drot.org,
	torvalds@...ux-foundation.org, segoon@...nwall.com,
	jmorris@...ei.org, scarybeasts@...il.com, avi@...hat.com,
	penberg@...helsinki.fi, viro@...iv.linux.org.uk, luto@....edu,
	mingo@...e.hu, akpm@...ux-foundation.org, khilman@...com,
	borislav.petkov@....com, amwang@...hat.com, ak@...ux.intel.com,
	eric.dumazet@...il.com, gregkh@...e.de, dhowells@...hat.com,
	daniel.lezcano@...e.fr, linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org, olofj@...omium.org,
	mhalcrow@...gle.com, dlaor@...hat.com
Subject: Re: [RFC,PATCH 1/2] seccomp_filters: system call filtering using
 BPF

> Thus, execv will not be a "special" case here. Seccomp either allows it
> or not. But also add a command to tell seccomp that this task will not
> be allowed to do anything privileged.

A setuid binary is not necessarily priviledged - indeed a root -> user
transition via setuid is pretty much the reverse.

It's a change of user context. Things like ptrace and file permissions
basically mean you can't build a barrier between stuff running as the
same uid to a great extent except with heavy restricting, but saying
"you can't become someone else" is very useful.

Alan
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