linux-kernel - [PATCH -mm 0/1] (Was: ptrace: unify FDPIC implementations)

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Message-ID: <20100522165320.GA19573@redhat.com>
Date:	Sat, 22 May 2010 18:53:20 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Roland McGrath <roland@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Mike Frysinger <vapier@...too.org>, linux-sh@...r.kernel.org,
	Paul Mundt <lethal@...ux-sh.org>,
	uclinux-dist-devel@...ckfin.uclinux.org,
	linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>
Subject: [PATCH -mm 0/1] (Was: ptrace: unify FDPIC implementations)

On 05/21, Roland McGrath wrote:
>
> > This looks unsafe. What protect child->mm if ptrace() races with SIGKILL ?
> >
> > Of course, I do not blame this patch, the code was copied from arch/, but
> > I think we need another patch which checks ->mm != NULL under task_lock()
> > on top of this one?
>
> Agreed, unless things are somehow different on nommu so there aren't such
> races.

I don't this !CONFG_MMU can make any difference, nothing can protect us
from exit_mm() afaics.

> But, as you mention, this is a long-standing issue that is entirely
> unrelated to the cleanup here and should not delay merging this patch.

Yes, yes, agreed.

Please see the patch on top of ptrace-unify-fdpic-implementations.patch
Untested, but hopefully trivial enough.

Oleg.

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