Date: Thu, 13 Sep 2018 14:05:54 +0200
From: Michal Kubecek <mkubecek@suse.cz>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: linux-wireless@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH 1/2] netlink: add NLA_REJECT policy type
Message-ID: <20180913120554.GG29691@unicorn.suse.cz> (sfid-20180913_140602_097920_C2850EB7)
References: <20180913084603.7979-1-johannes@sipsolutions.net>
 <20180913104955.GE29691@unicorn.suse.cz>
 <1536837915.4160.1.camel@sipsolutions.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
In-Reply-To: <1536837915.4160.1.camel@sipsolutions.net>
Sender: linux-wireless-owner@vger.kernel.org

On Thu, Sep 13, 2018 at 01:25:15PM +0200, Johannes Berg wrote:
> 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.

In ethtool (work in progress) I sometimes use extack message for
non-fatal warnings but AFAICS never before parsing the userspace
request (actually always shortly before returning). So I don't have
a problem with it.

Michal Kubecek