From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751401Ab1ADOT1 (ORCPT ); Tue, 4 Jan 2011 09:19:27 -0500 Received: from hera.kernel.org ([140.211.167.34]:32983 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750947Ab1ADOT0 (ORCPT ); Tue, 4 Jan 2011 09:19:26 -0500 Date: Tue, 4 Jan 2011 14:18:52 GMT From: tip-bot for Mike Galbraith Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, efault@gmx.de, oleg@redhat.com, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, efault@gmx.de, tglx@linutronix.de, oleg@redhat.com, mingo@elte.hu In-Reply-To: <1292508592.5940.28.camel@maggy.simson.net> References: <1292508592.5940.28.camel@maggy.simson.net> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched, autogroup: Fix potential access to freed memory Message-ID: Git-Commit-ID: 4f8219875a0dad2cfad9e93a3fafcd9626db98d2 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Tue, 04 Jan 2011 14:18:53 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 4f8219875a0dad2cfad9e93a3fafcd9626db98d2 Gitweb: http://git.kernel.org/tip/4f8219875a0dad2cfad9e93a3fafcd9626db98d2 Author: Mike Galbraith AuthorDate: Thu, 16 Dec 2010 15:09:52 +0100 Committer: Ingo Molnar CommitDate: Tue, 4 Jan 2011 15:10:34 +0100 sched, autogroup: Fix potential access to freed memory Oleg pointed out that the /proc interface kref_get() useage may race with the final put during autogroup_move_group(). A signal->autogroup assignment may be in flight when the /proc interface dereference, leaving them taking a reference to an already dead group. Reported-by: Oleg Nesterov Signed-off-by: Mike Galbraith Signed-off-by: Peter Zijlstra LKML-Reference: <1292508592.5940.28.camel@maggy.simson.net> Signed-off-by: Ingo Molnar --- kernel/sched_autogroup.c | 25 +++++++++++++++++-------- 1 files changed, 17 insertions(+), 8 deletions(-) diff --git a/kernel/sched_autogroup.c b/kernel/sched_autogroup.c index 57a7ac2..c80fedc 100644 --- a/kernel/sched_autogroup.c +++ b/kernel/sched_autogroup.c @@ -41,6 +41,20 @@ static inline struct autogroup *autogroup_kref_get(struct autogroup *ag) return ag; } +static inline struct autogroup *autogroup_task_get(struct task_struct *p) +{ + struct autogroup *ag; + unsigned long flags; + + if (!lock_task_sighand(p, &flags)) + return autogroup_kref_get(&autogroup_default); + + ag = autogroup_kref_get(p->signal->autogroup); + unlock_task_sighand(p, &flags); + + return ag; +} + static inline struct autogroup *autogroup_create(void) { struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL); @@ -149,11 +163,7 @@ EXPORT_SYMBOL(sched_autogroup_detach); void sched_autogroup_fork(struct signal_struct *sig) { - struct task_struct *p = current; - - spin_lock_irq(&p->sighand->siglock); - sig->autogroup = autogroup_kref_get(p->signal->autogroup); - spin_unlock_irq(&p->sighand->siglock); + sig->autogroup = autogroup_task_get(current); } void sched_autogroup_exit(struct signal_struct *sig) @@ -172,7 +182,6 @@ __setup("noautogroup", setup_autogroup); #ifdef CONFIG_PROC_FS -/* Called with siglock held. */ int proc_sched_autogroup_set_nice(struct task_struct *p, int *nice) { static unsigned long next = INITIAL_JIFFIES; @@ -194,7 +203,7 @@ int proc_sched_autogroup_set_nice(struct task_struct *p, int *nice) return -EAGAIN; next = HZ / 10 + jiffies; - ag = autogroup_kref_get(p->signal->autogroup); + ag = autogroup_task_get(p); down_write(&ag->lock); err = sched_group_set_shares(ag->tg, prio_to_weight[*nice + 20]); @@ -209,7 +218,7 @@ int proc_sched_autogroup_set_nice(struct task_struct *p, int *nice) void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m) { - struct autogroup *ag = autogroup_kref_get(p->signal->autogroup); + struct autogroup *ag = autogroup_task_get(p); down_read(&ag->lock); seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);