From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752665AbaKJWAm (ORCPT ); Mon, 10 Nov 2014 17:00:42 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53017 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752392AbaKJWAj (ORCPT ); Mon, 10 Nov 2014 17:00:39 -0500 Date: Mon, 10 Nov 2014 23:00:26 +0100 From: Oleg Nesterov To: Andrew Morton Cc: Aaron Tomlin , "Eric W. Biederman" , Peter Zijlstra , Roland McGrath , Sterling Alexander , linux-kernel@vger.kernel.org Subject: [PATCH 1/5] sched_show_task: fix unsafe usage of ->real_parent Message-ID: <20141110220026.GA31224@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141110215959.GA31106@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org rcu_read_lock() can not protect p->real_parent if release_task(p) was already called, change sched_show_task() to check pis_alive() like other users do. Note: we need some helpers to cleanup the code like this. And it seems that that the usage of cpu_curr(cpu) in dump_cpu_task() is not safe too. Signed-off-by: Oleg Nesterov --- kernel/sched/core.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 240157c..1ec75c9 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4572,8 +4572,10 @@ void sched_show_task(struct task_struct *p) #ifdef CONFIG_DEBUG_STACK_USAGE free = stack_not_used(p); #endif + ppid = 0; rcu_read_lock(); - ppid = task_pid_nr(rcu_dereference(p->real_parent)); + if (pid_alive(p)) + ppid = task_pid_nr(rcu_dereference(p->real_parent)); rcu_read_unlock(); printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free, task_pid_nr(p), ppid, -- 1.5.5.1