linux-kernel - Re: Compat 32-bit syscall entry from 64-bit task!? [was: Re: [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF]

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Message-ID: <20120123165644.GB13197@redhat.com>
Date:	Mon, 23 Jan 2012 17:56:44 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Chris Evans <scarybeasts@...il.com>
Cc:	Indan Zupancic <indan@....nu>, Andi Kleen <andi@...stfloor.org>,
	Jamie Lokier <jamie@...reable.org>,
	Andrew Lutomirski <luto@....edu>,
	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,
	rostedt@...dmis.org, jmorris@...ei.org, avi@...hat.com,
	penberg@...helsinki.fi, viro@...iv.linux.org.uk, 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,
	Roland McGrath <mcgrathr@...omium.org>
Subject: Re: Compat 32-bit syscall entry from 64-bit task!? [was: Re:
	[RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF]

On 01/18, Chris Evans wrote:
>
> Thanks, Oleg. Seems like this would be a nice change to have. As we
> can see, people do use ptrace() as a security technology.

OK, I'll send it.

> With this in place, you can also (where possible) set up the tracee
> with PR_SET_PDEATHSIG==SIGKILL. And then, you have defences again
> either of the tracer or tracee dying from a stray SIGKILL.

This can only help if the tracer is the natural parent, is it enough?

Indan suggested PTRACE_O_SIGKILL_ON_DEATH, perhaps it makes sense.

Oleg.

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