linux-kernel - Re: [PATCH 3/8] arm: Fix possible race on task->mm

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Date:	Wed, 8 Feb 2012 17:08:08 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Anton Vorontsov <anton.vorontsov@...aro.org>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Russell King <linux@....linux.org.uk>,
	Mike Frysinger <vapier@...too.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Richard Weinberger <richard@....at>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/8] arm: Fix possible race on task->mm

On 02/07, Anton Vorontsov wrote:
>
> Checking for task->mm is dangerous as ->mm might disappear (exit_mm()
> assigns NULL under task_lock(), so tasklist lock is not enough).
>
> We can't use get_task_mm()/mmput() pair as mmput() might sleep,

Yes, but

> so let's take the task lock while we care about its mm.

it seems that this needs find_lock_task_mm() too ?

the same for the rest patches in this series.

Oleg.

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