linux-kernel - Re: [PATCH v2 5/6] sched: Use rq->rd in sched

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Date:	Mon, 22 Sep 2014 22:34:49 +0400
From:	Kirill Tkhai <tkhai@...dex.ru>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Kirill Tkhai <ktkhai@...allels.com>
Subject: Re: [PATCH v2 5/6] sched: Use rq->rd in sched_setaffinity() under RCU read lock

22.09.2014, 22:32, "Kirill Tkhai" <tkhai@...dex.ru>:
> From: Kirill Tkhai <ktkhai@...allels.com>
>
> task_rq(p)->rd and task_rq(p)->rd->span may be used-after-free here.
> Probability of NULL pointer derefference isn't zero in this place.

Wrong comment, sorry. I'll resend

>
> Signed-off-by: Kirill Tkhai <ktkhai@...allels.com>
> Cc: <stable@...r.kernel.org> # v3.14+
> ---
>  kernel/sched/core.c |    9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 3b07710..643ee99 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -4023,13 +4023,14 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
>           * root_domain.
>           */
>  #ifdef CONFIG_SMP
> - if (task_has_dl_policy(p)) {
> - const struct cpumask *span = task_rq(p)->rd->span;
> -
> - if (dl_bandwidth_enabled() && !cpumask_subset(span, new_mask)) {
> + if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
> + rcu_read_lock();
> + if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
>                          retval = -EBUSY;
> + rcu_read_unlock();
>                          goto out_free_new_mask;
>                  }
> + rcu_read_unlock();
>          }
>  #endif
>  again:
>
> --
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