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

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Message-ID: <4F47BF56.6010602@linux.vnet.ibm.com>
Date:	Fri, 24 Feb 2012 08:48:22 -0800
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Christoph Lameter <cl@...ux.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 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
I was originally trying to address.

Acked-by: Dave Hansen <dave@...ux.vnet.ibm.com>

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