From: Andrew Morton <akpm@linux-foundation.org>
To: Christoph Lameter <cl@linux.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Dave Hansen <dave@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC][PATCH] fix move/migrate_pages() race on task struct
Date: Wed, 29 Feb 2012 12:31:20 -0800 [thread overview]
Message-ID: <20120229123120.127e21fd.akpm@linux-foundation.org> (raw)
In-Reply-To: <alpine.DEB.2.00.1202281329190.25590@router.home>
On Tue, 28 Feb 2012 13:30:19 -0600 (CST)
Christoph Lameter <cl@linux.com> wrote:
> Migration functions perform the rcu_read_unlock too early. As a result the
> task pointed to may change from under us.
>
> The following patch extend the period of the rcu_read_lock until after the
> permissions checks are done. We also take a refcount so that the task
> reference is stable when calling security check functions and performing
> cpuset node validation (which takes a mutex).
>
> The refcount is dropped before actual page migration occurs so there is no
> change to the refcounts held during page migration.
>
> Also move the determination of the mm of the task struct to immediately
> before the do_migrate*() calls so that it is clear that we switch from
> handling the task during permission checks to the mm for the actual
> migration. Since the determination is only done once and we then no longer
> use the task_struct we can be sure that we operate on a specific address
> space that will not change from under us.
What was the user-visible impact of the bug?
Please always include info this in bug fix changelogs - it helps me and
others to decide which kernel version(s) the patch should be merged
into.
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next prev parent reply other threads:[~2012-02-29 20:31 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-23 18:07 [RFC][PATCH] fix move/migrate_pages() race on task struct Dave Hansen
2012-02-23 18:45 ` Andi Kleen
2012-02-23 18:45 ` Christoph Lameter
2012-02-23 19:10 ` Dave Hansen
2012-02-23 19:40 ` Christoph Lameter
2012-02-23 20:04 ` Dave Hansen
2012-02-23 21:41 ` Christoph Lameter
2012-02-24 3:14 ` Eric W. Biederman
2012-02-24 15:20 ` Christoph Lameter
2012-02-24 15:41 ` Eric W. Biederman
2012-02-24 16:48 ` Dave Hansen
2012-02-24 16:54 ` Christoph Lameter
2012-02-24 17:04 ` Dave Hansen
2012-02-24 17:08 ` Christoph Lameter
2012-02-24 17:25 ` Dave Hansen
2012-02-24 17:32 ` Christoph Lameter
2012-02-24 21:37 ` Dave Hansen
2012-02-24 23:12 ` Eric W. Biederman
2012-02-27 16:43 ` Christoph Lameter
2012-02-25 12:13 ` Eric W. Biederman
2012-02-27 19:01 ` Christoph Lameter
2012-02-27 20:15 ` Eric W. Biederman
2012-02-27 22:39 ` Christoph Lameter
2012-02-28 19:30 ` Christoph Lameter
2012-02-29 20:31 ` Andrew Morton [this message]
2012-02-29 20:33 ` Christoph Lameter
2012-02-29 20:36 ` Dave Hansen
2012-02-24 17:07 ` KOSAKI Motohiro
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