linux-kernel - Re: [PATCH 06/14] net: sched: implement reference counted action release

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Message-ID: <vbfr2m6a8z2.fsf@reg-r-vrt-018-180.mtr.labs.mlnx>
Date:   Sun, 20 May 2018 13:59:29 +0300
From:   Vlad Buslov <vladbu@...lanox.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        netdev@...r.kernel.org, davem@...emloft.net, jhs@...atatu.com,
        xiyou.wangcong@...il.com, pablo@...filter.org,
        kadlec@...ckhole.kfki.hu, fw@...len.de, ast@...nel.org,
        daniel@...earbox.net, edumazet@...gle.com, keescook@...omium.org,
        linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, kliteyn@...lanox.com
Subject: Re: [PATCH 06/14] net: sched: implement reference counted action release


On Sun 20 May 2018 at 06:22, Jiri Pirko <jiri@...nulli.us> wrote:
> Sat, May 19, 2018 at 11:43:27PM CEST, marcelo.leitner@...il.com wrote:
>>On Mon, May 14, 2018 at 05:27:07PM +0300, Vlad Buslov wrote:
>>...
>>> @@ -1052,6 +1088,36 @@ static int tca_action_flush(struct net *net, struct nlattr *nla,
>>>  	return err;
>>>  }
>>>
>>> +static int tcf_action_delete(struct net *net, struct list_head *actions,
>>> +			     struct netlink_ext_ack *extack)
>>> +{
>>> +	int ret;
>>
>>Reverse christmass tree.. this line should be the last in variable
>>declarations.
>>
>>> +	struct tc_action *a, *tmp;
>>> +	char kind[IFNAMSIZ];
>>> +	u32 act_index;
>>> +
>>> +	list_for_each_entry_safe(a, tmp, actions, list) {
>>> +		const struct tc_action_ops *ops = a->ops;
>>> +
>>> +		/* Actions can be deleted concurrently
>>> +		 * so we must save their type and id to search again
>>> +		 * after reference is released.
>>> +		 */
>>> +		strncpy(kind, a->ops->kind, sizeof(kind) - 1);
>>
>>This may be problematic. Why strncpy here?
>
> This is not necessary if Vlad is going to hold module referece, ops
> cannot disappear.

Yes, I've already refactored this code to reuse ops.

>
>
>>
>>a->ops->kind is also of size IFNAMSIZ. If a->ops->kind is actually
>>IFNAMSIZ-1 long, kind here won't be NULL terminated, as kind is not
>>initialized and strncpy won't add the NULL.
>>
>>> +		act_index = a->tcfa_index;
>>> +
>>> +		list_del(&a->list);
>>> +		if (tcf_action_put(a))
>>> +			module_put(ops->owner);
>>> +
>>> +		/* now do the delete */
>>> +		ret = tcf_action_del_1(net, kind, act_index, extack);
>>> +		if (ret < 0)
>>> +			return ret;
>>> +	}
>>> +	return 0;
>>> +}