linux-kernel - Re: [RFC][PATCH] fix move/migrate

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Message-ID: <alpine.DEB.2.00.1202241053220.3726@router.home>
Date:	Fri, 24 Feb 2012 10:54:15 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC][PATCH] fix move/migrate_pages() race on task struct

On Fri, 24 Feb 2012, Dave Hansen wrote:

> On 02/24/2012 07:20 AM, Christoph Lameter wrote:
> > Subject: migration: Do not do rcu_read_unlock until the last time we need the task_struct pointer
> >
> > Migration functions perform the rcu_read_unlock too early. As a result the
> > task pointed to may change. Bugs were introduced when adding security checks
> > because rcu_unlock/lock sequences were inserted. Plus the security checks
> > and do_move_pages used the task_struct pointer after rcu_unlock.
> >
> > Fix those issues by removing the unlock/lock sequences and moving the
> > rcu_read_unlock after the last use of the task struct pointer.
> >
> > Signed-off-by: Christoph Lameter <cl@...ux.com>
>
> It doesn't fix the code duplication, but it definitely does fix the bug

Yes I did not want to override all your good work.

Could you do another patch that removed the duplication?

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