linux-kernel - Re: [patch] let CONFIG

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Message-Id: <E1G2RQL-0000tG-Gb@be1.lrz>
Date:	Mon, 17 Jul 2006 13:37:44 +0200
From:	Bodo Eggert <7eggert@...tempel.de>
To:	Ingo Molnar <mingo@...e.hu>, Jeff Dike <jdike@...toit.com>,
	Andrea Arcangeli <andrea@...e.de>, Andi Kleen <ak@...e.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arjan van de Ven <arjan@...radead.org>,
	Adrian Bunk <bunk@...sta.de>, Andrew Morton <akpm@...l.org>,
	Lee Revell <rlrevell@...-job.com>,
	linux-kernel@...r.kernel.org, Alan Cox <alan@...hat.com>,
	Linus Torvalds <torvalds@...l.org>
Subject: Re: [patch] let CONFIG_SECCOMP default to n

Ingo Molnar <mingo@...e.hu> wrote:
> * Jeff Dike <jdike@...toit.com> wrote:

>> Now, there were a couple of ways to legitimately escape from UML, and
>> they *did* involve ptrace.  Things like single-stepping a system call
>> instruction or putting a breakpoint on a system call instruction and
>> single-stepping from the breakpoint.  As far as I know, these were
>> discovered and fixed by UML developers before there was any outside
>> awareness of these bugs.
> 
> also, UML 'ptrace clients' are allowed alot more leeway than what a
> seccomp-alike ptrace/utrace based syscall filter would allow. It would
> clearly exclude activities like 'setting a breakpoint' or
> 'single-stepping' - valid syscalls would be limited to
> read/write/sigreturn/exit.

So instead of breakpointing (using int3), you'd have to write
'mv flag I_AM_HERE;self:jmp self' and resort to polling?
This would not prevent (ab)use except for some corner cases.
-- 
Ich danke GMX dafür, die Verwendung meiner Adressen mittels per SPF
verbreiteten Lügen zu sabotieren.

http://david.woodhou.se/why-not-spf.html
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