netdev - Re: [PATCH 1/2] netlink: add NLA

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Date:   Thu, 13 Sep 2018 13:25:15 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 1/2] netlink: add NLA_REJECT policy type

On Thu, 2018-09-13 at 12:49 +0200, Michal Kubecek wrote:

> >  		if (type > 0 && type <= maxtype) {
> >  			if (policy) {
> > -				err = validate_nla(nla, maxtype, policy);
> > +				err = validate_nla(nla, maxtype, policy,
> > +						   extack);
> >  				if (err < 0) {
> > -					NL_SET_ERR_MSG_ATTR(extack, nla,
> > -							    "Attribute failed policy validation");
> > +					NL_SET_BAD_ATTR(extack, nla);
> > +					if (extack && !extack->_msg)
> > +						NL_SET_ERR_MSG(extack,
> > +							       "Attribute failed policy validation");
> >  					goto errout;
> >  				}
> >  			}
> > -- 
> 
> Technically, this would change the outcome when nla_parse() is called
> with extack->_msg already set nad validate_nla() fails on something else
> than NLA_REJECT; it will preserve the previous message in such case.
> But I don't think this is a serious problem.

Yes, that's true. I looked at quite a few of the setters just now (there
are ~500 already, wow!), and they all set & return, so this shouldn't be
an issue.

johannes