Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756686Ab2BGGvp (ORCPT ); Tue, 7 Feb 2012 01:51:45 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:61195 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756537Ab2BGGvo (ORCPT ); Tue, 7 Feb 2012 01:51:44 -0500 Date: Tue, 7 Feb 2012 10:51:41 +0400 From: Anton Vorontsov To: Oleg Nesterov Cc: Greg KH , KOSAKI Motohiro , "Eric W. Biederman" , "Paul E. McKenney" , Paul Mundt , Russell King , Mike Frysinger , Benjamin Herrenschmidt , Richard Weinberger , linux-kernel@vger.kernel.org Subject: [PATCH 8/8] um: Fix possible race on task->mm Message-ID: <20120207065141.GH1496@oksana.dev.rtsoft.ru> References: <20120207064809.GA29061@oksana.dev.rtsoft.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20120207064809.GA29061@oksana.dev.rtsoft.ru> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1168 Lines: 38 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. Signed-off-by: Anton Vorontsov --- arch/um/kernel/reboot.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/um/kernel/reboot.c b/arch/um/kernel/reboot.c index 66d754c..1411f4e 100644 --- a/arch/um/kernel/reboot.c +++ b/arch/um/kernel/reboot.c @@ -25,10 +25,13 @@ static void kill_off_processes(void) read_lock(&tasklist_lock); for_each_process(p) { - if (p->mm == NULL) + task_lock(p); + if (!p->mm) { + task_unlock(p); continue; - + } pid = p->mm->context.id.u.pid; + task_unlock(p); os_kill_ptraced_process(pid, 1); } read_unlock(&tasklist_lock); -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/