linux-kernel - Re: [PATCH] sched/dl: Fix race between dl_task_timer() and sched

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 19 May 2014 15:12:33 +0200
From:	Juri Lelli <juri.lelli@...il.com>
To:	Kirill Tkhai <tkhai@...dex.ru>
Cc:	linux-kernel@...r.kernel.org, peterz@...radead.org,
	mingo@...hat.com, stable@...r.kernel.org
Subject: Re: [PATCH] sched/dl: Fix race between dl_task_timer() and
 sched_setaffinity()

On Sat, 17 May 2014 01:30:03 +0400
Kirill Tkhai <tkhai@...dex.ru> wrote:

> The race is in unlocked task_rq() access. In pair with parallel
> call of sched_setaffinity() it may be a reason of corruption
> of internal rq's data.
> 

Sure, the thing can happen!

> Signed-off-by: Kirill Tkhai <tkhai@...dex.ru>
> CC: Juri Lelli <juri.lelli@...il.com>
> CC: Peter Zijlstra <peterz@...radead.org>
> CC: Ingo Molnar <mingo@...hat.com>
> Cc: <stable@...r.kernel.org> # v3.14
> ---
>  kernel/sched/deadline.c |    9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 800e99b..ffb023a 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -513,9 +513,16 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
>  						     struct sched_dl_entity,
>  						     dl_timer);
>  	struct task_struct *p = dl_task_of(dl_se);
> -	struct rq *rq = task_rq(p);
> +	struct rq *rq;

We could maybe add a comment here, in line with what we have below, to
document why we need this.

Thanks,

- Juri

> +again:
> +	rq = task_rq(p);
>  	raw_spin_lock(&rq->lock);
>  
> +	if (unlikely(rq != task_rq(p))) {
> +		raw_spin_unlock(&rq->lock);
> +		goto again;
> +	}
> +
>  	/*
>  	 * We need to take care of a possible races here. In fact, the
>  	 * task might have changed its scheduling policy to something
> 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/