Re: [PATCH 1/1] mm_for_maps: simplify, use ptrace_may_access()

From: James Morris <jmorris@namei.org>
To: "Serge E. Hallyn" <serue@us.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Christoph Hellwig <hch@infradead.org>,
	Ingo Molnar <mingo@elte.hu>, Chris Wright <chrisw@sous-sol.org>,
	Roland McGrath <roland@redhat.com>,
	linux-kernel@vger.kernel.org, Al Viro <viro@ZenIV.linux.org.uk>,
	linux-security-module@vger.kernel.org
Subject: Re: [PATCH 1/1] mm_for_maps: simplify, use ptrace_may_access()
Date: Thu, 25 Jun 2009 00:21:57 +1000 (EST)	[thread overview]
Message-ID: <alpine.LRH.2.00.0906250021460.20443@tundra.namei.org> (raw)
In-Reply-To: <20090624030627.GA6459@us.ibm.com>

On Tue, 23 Jun 2009, Serge E. Hallyn wrote:

> Quoting Oleg Nesterov (oleg@redhat.com):
> > It would be nice to kill __ptrace_may_access(). It requires task_lock(),
> > but this lock is only needed to read mm->flags in the middle.
> > 
> > Convert mm_for_maps() to use ptrace_may_access(), this also simplifies
> > the code a little bit.
> > 
> > Also, we do not need to take ->mmap_sem in advance. In fact I think
> > mm_for_maps() should not play with ->mmap_sem at all, the caller should
> > take this lock.
> 
> Yeah I think that makes sense.
> 
> > With or without this patch, without ->cred_guard_mutex held we can race
> > with exec() and get the new ->mm but check old creds.
> > 
> > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> 
> reasoning on the security check also makes sense.
> 
> Reviewed-by: Serge Hallyn <serue@us.ibm.com>


Applied to
git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6#next


-- 
James Morris
<jmorris@namei.org>