netdev - Re: [PATCH net] qdisc: fix a module refcount leak in qdisc_create

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Date:   Thu, 25 Aug 2016 21:26:59 +0800
From:   Wei Yongjun <weiyj.lk@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        John Fastabend <john.fastabend@...il.com>,
        stephen hemminger <stephen@...workplumber.org>,
        Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [PATCH net] qdisc: fix a module refcount leak in
 qdisc_create_dflt()

On 08/25/2016 12:39 AM, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> Should qdisc_alloc() fail, we must release the module refcount
> we got right before.
>
> Fixes: 6da7c8fcbcbd ("qdisc: allow setting default queuing discipline")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
>  net/sched/sch_generic.c |    9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
> index e95b67cd5718..657c13362b19 100644
> --- a/net/sched/sch_generic.c
> +++ b/net/sched/sch_generic.c
> @@ -643,18 +643,19 @@ struct Qdisc *qdisc_create_dflt(struct netdev_queue *dev_queue,
>  	struct Qdisc *sch;
>  
>  	if (!try_module_get(ops->owner))
> -		goto errout;
> +		return NULL;
>  
>  	sch = qdisc_alloc(dev_queue, ops);
> -	if (IS_ERR(sch))
> -		goto errout;
> +	if (IS_ERR(sch)) {
> +		module_put(ops->owner);
> +		return NULL;
> +	}
>  	sch->parent = parentid;
>  
>  	if (!ops->init || ops->init(sch, NULL) == 0)
>  		return sch;
>  
>  	qdisc_destroy(sch);

ops->init() failed, missing module_put() here.


> -errout:
>  	return NULL;
>  }
>  EXPORT_SYMBOL(qdisc_create_dflt);
>
>
> .
>