netdev - Re: [PATCH v1] net/sched: mqprio: Add length check for TCA_MQPRIO_{MAX/MIN}

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Date: Mon, 24 Jul 2023 09:19:14 +0800 (GMT+08:00)
From: "Lin Ma" <linma@....edu.cn>
To: "Victor Nogueira" <victor@...atatu.com>
Cc: jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] net/sched: mqprio: Add length check for
 TCA_MQPRIO_{MAX/MIN}_RATE64

Hello Victor,

>
> Shouldn't the check be nla_len(attr) != sizeof(u64)?
> An attribute with a bigger length also seems to be invalid.
> 
> You could also separate this check into another if statement,
> so that the error message is clearer in regards to why the attr is
> invalid. Something like:
> 
> if (nla_len(attr) != sizeof(u64)) {
>          NL_SET_ERR_MSG_ATTR_FMT(extack, attr,
>                                  "Attribute length expected to be %lu",
>                                  sizeof(u64));
>          return -EINVAL;
> }
> 
> >   				NL_SET_ERR_MSG_ATTR(extack, attr,
> >   						    "Attribute type expected to be TCA_MQPRIO_MIN_RATE64");
> >   				return -EINVAL;
> > @@ -307,7 +308,8 @@ static int mqprio_parse_nlattr(struct Qdisc *sch, struct tc_mqprio_qopt *qopt,
> >   		i = 0;
> >   		nla_for_each_nested(attr, tb[TCA_MQPRIO_MAX_RATE64],
> >   				    rem) {
> > -			if (nla_type(attr) != TCA_MQPRIO_MAX_RATE64) {
> > +			if (nla_type(attr) != TCA_MQPRIO_MAX_RATE64 ||
> > +			    nla_len(attr) < sizeof(u64)) {
> 
> Same as the previous comment.
> 
> >   				NL_SET_ERR_MSG_ATTR(extack, attr,
> >   						    "Attribute type expected to be TCA_MQPRIO_MAX_RATE64");
> >   				return -EINVAL;
> 
> cheers,
> Victor

Yeah, I use < instead of != for a looser check. I agree with you the "!=" condition and the separation suggestion.
I will prepare the v2 ASAP.

Thanks
Lin