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From: "Paul Menage" <menage@google.com>
To: balbir@in.ibm.com
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
	vatsa@in.ibm.com, ckrm-tech@lists.sourceforge.net, xemul@sw.ru,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	svaidy@linux.vnet.ibm.com, devel@openvz.org
Subject: Re: [ckrm-tech] [RFC][PATCH][2/4] Add RSS accounting and control
Date: Mon, 19 Feb 2007 04:09:38 -0800	[thread overview]
Message-ID: <6599ad830702190409x4f64e56ex4044a12d949e44af@mail.gmail.com> (raw)
In-Reply-To: <45D9906F.2090605@in.ibm.com>

On 2/19/07, Balbir Singh <balbir@in.ibm.com> wrote:
> >
> > More worrisome is the potential for use-after-free.  What prevents the
> > pointer at mm->container from referring to freed memory after we're dropped
> > the lock?
> >
>
> The container cannot be freed unless all tasks holding references to it are
> gone,

... or have been moved to other containers. If you're not holding
task->alloc_lock or one of the container mutexes, there's nothing to
stop the task being moved to another container, and the container
being deleted.

If you're in an RCU section then you can guarantee that the container
(that you originally read from the task) and its subsystems at least
won't be deleted while you're accessing them, but for accounting like
this I suspect that's not enough, since you need to be adding to the
accounting stats on the correct container. I think you'll need to hold
mm->container_lock for the duration of memctl_update_rss()

Paul

  reply	other threads:[~2007-02-19 12:09 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-19  6:50 [RFC][PATCH][0/4] Memory controller (RSS Control) Balbir Singh
2007-02-19  6:50 ` [RFC][PATCH][1/4] RSS controller setup Balbir Singh
2007-02-19  8:57   ` Andrew Morton
2007-02-19  9:18     ` Paul Menage
2007-02-19 11:13       ` Balbir Singh
2007-02-19 19:43         ` Matthew Helsley
2007-02-19 10:06     ` Balbir Singh
2007-02-19  6:50 ` [RFC][PATCH][2/4] Add RSS accounting and control Balbir Singh
2007-02-19  8:58   ` Andrew Morton
2007-02-19 10:37     ` [ckrm-tech] " Balbir Singh
2007-02-19 11:01       ` Andrew Morton
2007-02-19 11:09         ` Balbir Singh
2007-02-19 11:23           ` Andrew Morton
2007-02-19 11:56             ` Balbir Singh
2007-02-19 12:09               ` Paul Menage [this message]
2007-02-19 14:10                 ` Balbir Singh
2007-02-19 16:07                   ` Vaidyanathan Srinivasan
2007-02-19 16:17                     ` Balbir Singh
2007-02-20  6:40                       ` Vaidyanathan Srinivasan
2007-02-19  6:50 ` [RFC][PATCH][3/4] Add reclaim support Balbir Singh
2007-02-19  8:59   ` Andrew Morton
2007-02-19 10:50     ` Balbir Singh
2007-02-19 11:10       ` Andrew Morton
2007-02-19 11:16         ` Balbir Singh
2007-02-19  9:48   ` KAMEZAWA Hiroyuki
2007-02-19 10:52     ` Balbir Singh
2007-02-19  6:50 ` [RFC][PATCH][4/4] RSS controller documentation Balbir Singh
2007-02-19  8:54 ` [RFC][PATCH][0/4] Memory controller (RSS Control) Andrew Morton
2007-02-19  9:06   ` Paul Menage
2007-02-19  9:50     ` [ckrm-tech] " Kirill Korotaev
2007-02-19  9:50       ` Paul Menage
2007-02-19 10:24       ` Balbir Singh
2007-02-19 10:39     ` Balbir Singh
2007-02-19  9:16   ` Magnus Damm
2007-02-19 10:45     ` Balbir Singh
2007-02-19 11:56       ` Magnus Damm
2007-02-19 14:07         ` Balbir Singh
2007-02-19 10:00   ` Balbir Singh

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