linux-kernel - Re: [PATCH 08/10] um: Fix possible race on task->mm

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Message-ID: <4F6DAC0C.4010203@nod.at>
Date:	Sat, 24 Mar 2012 12:12:12 +0100
From:	Richard Weinberger <richard@....at>
To:	Anton Vorontsov <anton.vorontsov@...aro.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Russell King <linux@....linux.org.uk>,
	Mike Frysinger <vapier@...too.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	John Stultz <john.stultz@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	uclinux-dist-devel@...ckfin.uclinux.org,
	linuxppc-dev@...ts.ozlabs.org, linux-sh@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net, linux-mm@...ck.org
Subject: Re: [PATCH 08/10] um: Fix possible race on task->mm

Am 24.03.2012 11:30, schrieb Anton Vorontsov:
> 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,
> so let's take the task lock while we care about its mm.
> 
> Note that we should also use find_lock_task_mm() to check all process'
> threads for a valid mm, but for uml we'll do it in a separate patch.
> 
> Signed-off-by: Anton Vorontsov <anton.vorontsov@...aro.org>

Acked-by: Richard Weinberger <richard@....at>

Thanks,
//richard


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