linux-kernel - Re: [PATCH 1/1] sched/autogroup: Fix race with task

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Message-ID: <20130527090338.GG2781@laptop>
Date:	Mon, 27 May 2013 11:03:38 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Gerald Schaefer <gerald.schaefer@...ibm.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Li Zefan <lizefan@...wei.com>,
	linux-kernel@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH 1/1] sched/autogroup: Fix race with task_groups list

On Fri, May 24, 2013 at 06:07:49PM +0200, Gerald Schaefer wrote:
> In autogroup_create(), a tg is allocated and added to the task_groups
> list. If CONFIG_RT_GROUP_SCHED is set, this tg is then modified while on
> the list, without locking. This can race with someone walking the list,
> like __enable_runtime() during CPU unplug, and result in a use-after-free
> bug.
> 
> To fix this, move sched_online_group(), which adds the tg to the list,
> to the end of the autogroup_create() function after the modification.
> 
> Signed-off-by: Gerald Schaefer <gerald.schaefer@...ibm.com>

Ah indeed, nice catch. Thanks!
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