linux-kernel - Re: Compat 32-bit syscall entry from 64-bit task!?

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Date:	Mon, 23 Jan 2012 17:48:15 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Indan Zupancic <indan@....nu>
Cc:	Jamie Lokier <jamie@...reable.org>,
	Roland McGrath <mcgrathr@...gle.com>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.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,
	segoon@...nwall.com, rostedt@...dmis.org, jmorris@...ei.org,
	scarybeasts@...il.com, 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
Subject: Re: Compat 32-bit syscall entry from 64-bit task!?

On 01/23, Indan Zupancic wrote:
>
> On Sat, January 21, 2012 02:23, Jamie Lokier wrote:
> >
> > (Fwiw, two other issues with arch-independent ptrace have come up in this
> > thread, which ought to be fairly easy to fix:
> >    - If tracer dies, tracee is free to continue running.  For security
> >      tracers, and would be useful for strace as well, it would be good
> >      to have an option to SIGKILL the tracee if tracer dies.
>
> It should be easy to add a PTRACE_O_SIGKILL_ON_DEATH option.

Yes, this looks simple.

> >    - Can't abort or change an unwanted syscall if the process receives
> >      SIGKILL as it's about to start a syscall (which will be its last).)
>
> This is very important for any syscall filtering/control via ptrace, otherwise
> SIGKILL becomes a security problem. Oleg had a patch for that:

OK, I'll send this patch after some testing. Although it looks trivial.

Oleg.

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