From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx111.postini.com [74.125.245.111]) by kanga.kvack.org (Postfix) with SMTP id 7D3446B004A for ; Fri, 24 Feb 2012 11:48:31 -0500 (EST) Received: from /spool/local by e7.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 24 Feb 2012 11:48:30 -0500 Received: from d01relay06.pok.ibm.com (d01relay06.pok.ibm.com [9.56.227.116]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id 144216E804A for ; Fri, 24 Feb 2012 11:48:27 -0500 (EST) Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay06.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q1OGmQWq2801856 for ; Fri, 24 Feb 2012 11:48:26 -0500 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q1OGmQRQ031216 for ; Fri, 24 Feb 2012 11:48:26 -0500 Message-ID: <4F47BF56.6010602@linux.vnet.ibm.com> Date: Fri, 24 Feb 2012 08:48:22 -0800 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [RFC][PATCH] fix move/migrate_pages() race on task struct References: <20120223180740.C4EC4156@kernel> <4F468F09.5050200@linux.vnet.ibm.com> <4F469BC7.50705@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: "Eric W. Biederman" , linux-kernel@vger.kernel.org, linux-mm@kvack.org 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 It doesn't fix the code duplication, but it definitely does fix the bug I was originally trying to address. Acked-by: Dave Hansen -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org