linux-kernel - Re: [PATCH] Yama: access current->comm directly

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Message-ID: <20120730225037.4c8dd450@ultron>
Date:	Mon, 30 Jul 2012 22:50:37 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	John Johansen <john.johansen@...onical.com>
Cc:	Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
	James Morris <james.l.morris@...cle.com>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH] Yama: access current->comm directly

On Mon, 30 Jul 2012 14:21:33 -0700
John Johansen <john.johansen@...onical.com> wrote:

> On 07/30/2012 09:58 AM, Kees Cook wrote:
> > The core ptrace access checking routine already holds the task lock,
> > so there is no need to use get_task_comm() which just tries to take the
> > lock again. Drop its use and access current->comm directly.
> > 
> > Reported-by: Fengguang Wu <fengguang.wu@...el.com>
> > Suggested-by: Oleg Nesterov <oleg@...hat.com>
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> yep, looks good
> 
> Acked-by: John Johansen <john.johansen@...onical.com>


Code looks correct but having a weird cornercase direct reference is
asking for an accident later. For maintainability I'd rather see that as
__get_task_comm() or get_task_commu_unlocked() which does the job, deals
with all the edge cases and contains a WARN_ON check on the lock.

Alan
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