From: Kirill Tkhai <ktkhai@parallels.com>
To: Sasha Levin <sasha.levin@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>, "Ingo Molnar" <mingo@redhat.com>,
Vladimir Davydov <vdavydov@parallels.com>,
"Kirill Tkhai" <tkhai@yandex.ru>
Subject: Re: [PATCH v4] sched/numa: fix unsafe get_task_struct() in task_numa_assign()
Date: Wed, 12 Nov 2014 12:49:32 +0300 [thread overview]
Message-ID: <1415785772.15631.23.camel@tkhai> (raw)
In-Reply-To: <2477901415649681@web30o.yandex.ru>
В Пн, 10/11/2014 в 23:01 +0300, Kirill Tkhai пишет:
>
> 10.11.2014, 19:45, "Sasha Levin" <sasha.levin@oracle.com>:
> > On 11/10/2014 11:36 AM, Kirill Tkhai wrote:
> >> I mean task_numa_find_cpu(). If a garbage is in cpumask_of_node(env->dst_nid)
> >> and cpu is bigger than mask, the check
> >>
> >> cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)
> >>
> >> may be true.
> >>
> >> So, we dereference wrong rq in task_numa_compare(). It's not rq at all.
> >> Strange cpu may be from here. It's just a int number in a wrong memory.
> >
> > But the odds of the spinlock magic and owner pointer matching up are slim
> > to none in that case. The memory is also likely to be valid since KASAN didn't
> > complain about the access, so I don't believe it to be an access to freed memory.
>
> I'm not good with lockdep checks, so I can't judge right now...
> Just a hypothesis.
>
> >> A hypothesis that below may help:
> >>
> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> >> index 826fdf3..a2b4a8a 100644
> >> --- a/kernel/sched/fair.c
> >> +++ b/kernel/sched/fair.c
> >> @@ -1376,6 +1376,9 @@ static void task_numa_find_cpu(struct task_numa_env *env,
> >> {
> >> int cpu;
> >>
> >> + if (!node_online(env->dst_nid))
> >> + return;
> >
> > I've changed that to BUG_ON(!node_online(env->dst_nid)) and will run it for a
> > bit.
>
> I've looked one more time, and it looks like it's better to check for
> BUG_ON(env->dst_nid > MAX_NUMNODES). node_online() may do not work for
> insane nids.
>
> Anyway, even if it's not connected, we need to initialize numa_preferred_nid
> of init_task, because it's inherited by kernel_init() (and /sbin/init too).
> I'll send the patch tomorrow.
Also we can check for cpu. A problem may be in how nodes are built etc..
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 826fdf3..8f5c316 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1381,6 +1381,14 @@ static void task_numa_find_cpu(struct task_numa_env *env,
if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
continue;
+ /*
+ * Is cpumask_of_node() broken? In sched_init() we
+ * initialize only possible RQs (their rq->lock etc).
+ */
+ BUG_ON(cpu >= NR_CPUS || !cpu_possible(cpu));
+ /* Insane node id? */
+ BUG_ON(env->dst_nid >= MAX_NUMNODES || !node_online(env->dst_nid));
+
env->dst_cpu = cpu;
task_numa_compare(env, taskimp, groupimp);
}
next prev parent reply other threads:[~2014-11-12 9:49 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-22 7:17 [PATCH v4] sched/numa: fix unsafe get_task_struct() in task_numa_assign() Kirill Tkhai
2014-10-22 21:30 ` introduce task_rcu_dereference? Oleg Nesterov
2014-10-22 22:23 ` Oleg Nesterov
2014-10-23 18:15 ` Oleg Nesterov
2014-10-23 8:10 ` Kirill Tkhai
2014-10-23 18:18 ` Oleg Nesterov
2014-10-24 7:51 ` Kirill Tkhai
2014-10-27 19:53 ` [PATCH 0/3] introduce task_rcu_dereference() Oleg Nesterov
2014-10-27 19:54 ` [PATCH 1/3] probe_kernel_address() can use __probe_kernel_read() Oleg Nesterov
2014-10-27 19:54 ` [PATCH 2/3] introduce probe_slab_address() Oleg Nesterov
2014-10-27 19:21 ` Christoph Lameter
2014-10-28 5:44 ` Kirill Tkhai
2014-10-28 5:48 ` Kirill Tkhai
2014-10-28 15:01 ` Peter Zijlstra
2014-10-28 17:56 ` Kirill Tkhai
2014-10-28 18:00 ` Kirill Tkhai
2014-10-28 19:55 ` Oleg Nesterov
2014-10-28 20:12 ` Oleg Nesterov
2014-10-29 5:10 ` Kirill Tkhai
2014-10-27 19:54 ` [PATCH 3/3] introduce task_rcu_dereference() Oleg Nesterov
2014-10-28 6:22 ` Kirill Tkhai
2016-05-18 17:02 ` Peter Zijlstra
2016-05-18 18:23 ` Oleg Nesterov
2016-05-18 19:10 ` Peter Zijlstra
2016-05-18 19:57 ` Oleg Nesterov
2016-05-26 11:34 ` Peter Zijlstra
2016-06-03 10:49 ` [tip:sched/core] sched/fair: Use task_rcu_dereference() tip-bot for Oleg Nesterov
2016-06-03 10:48 ` [tip:sched/core] sched/api: Introduce task_rcu_dereference() and try_get_task_struct() tip-bot for Oleg Nesterov
2014-10-28 11:02 ` [tip:sched/core] sched/numa: Fix unsafe get_task_struct() in task_numa_assign() tip-bot for Kirill Tkhai
2014-11-08 3:48 ` [PATCH v4] sched/numa: fix " Sasha Levin
2014-11-09 14:07 ` Kirill Tkhai
2014-11-10 10:03 ` Peter Zijlstra
2014-11-10 15:48 ` Sasha Levin
2014-11-10 16:01 ` Peter Zijlstra
2014-11-16 9:50 ` [tip:sched/urgent] sched/numa: Avoid selecting oneself as swap target tip-bot for Peter Zijlstra
2014-11-10 16:03 ` [PATCH v4] sched/numa: fix unsafe get_task_struct() in task_numa_assign() Peter Zijlstra
2014-11-10 16:09 ` Sasha Levin
2014-11-10 16:16 ` Peter Zijlstra
2014-11-10 16:10 ` Kirill Tkhai
2014-11-10 16:36 ` Kirill Tkhai
2014-11-10 16:44 ` Sasha Levin
2014-11-10 20:01 ` Kirill Tkhai
2014-11-12 9:49 ` Kirill Tkhai [this message]
2014-11-15 2:38 ` Sasha Levin
2014-11-18 17:30 ` Sasha Levin
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