Re: [PATCH 3/3] ptrace: do not use task_lock() for attach

From: James Morris <jmorris@namei.org>
To: Chris Wright <chrisw@sous-sol.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Roland McGrath <roland@redhat.com>,
	linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	Eric Paris <eparis@redhat.com>,
	Stephen Smalley <sds@tycho.nsa.gov>,
	David Howells <dhowells@redhat.com>
Subject: Re: [PATCH 3/3] ptrace: do not use task_lock() for attach
Date: Thu, 7 May 2009 09:48:29 +1000 (EST)	[thread overview]
Message-ID: <alpine.LRH.2.00.0905070946480.22586@tundra.namei.org> (raw)
In-Reply-To: <20090506232703.GA3036@sequoia.sous-sol.org>

On Wed, 6 May 2009, Chris Wright wrote:

> * Oleg Nesterov (oleg@redhat.com) wrote:
> > But this can happen without this change too?
> > 
> > - cpu2 takes task_lock(), tracehook_tracer_task() returns NULL because
> >   we are not traced yet.
> > 
> > - cpu1 does ptrace_attach() and succeds, because cpu2 didn't update sid
> >   yet
> > 
> > - cpu2 continues, it doesn't check avc_has_perm() (tracer == 0) and
> >   updates sid.
> > 
> > No?
> 
> Yes.
> 
> > Shouldn't selinux_setprocattr() take ->cred_exec_mutex, like we do in
> > selinux_bprm_set_creds() path?
> 
> I was looking at the same, seems like it to me.  James?

As far as I can tell, yes.

(Added David Howells and security folk to the cc -- please make sure at 
least that the LSM list is cc'd when changing code which affects LSM 
modules).

- James
-- 
James Morris
<jmorris@namei.org>