netdev - Re: [PATCH net-next 04/13] genetlink: load policy based on validation flags

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Date:   Wed, 19 Oct 2022 12:20:39 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
        pabeni@...hat.com, jiri@...nulli.us, razor@...ckwall.org,
        nicolas.dichtel@...nd.com, gnault@...hat.com,
        jacob.e.keller@...el.com, fw@...len.de
Subject: Re: [PATCH net-next 04/13] genetlink: load policy based on
 validation flags

On Wed, 19 Oct 2022 10:01:04 +0200 Johannes Berg wrote:
> On Tue, 2022-10-18 at 16:07 -0700, Jakub Kicinski wrote:
> > Set the policy and maxattr pointers based on validation flags.  
> 
> I feel like you could have more commit message here
> 
> >  	ops = ctx->ops;
> > -	if (ops->validate & GENL_DONT_VALIDATE_DUMP)
> > -		goto no_attrs;
> > -
> > -	if (ctx->nlh->nlmsg_len < nlmsg_msg_size(ctx->hdrlen))
> > +	if (!(ops->validate & GENL_DONT_VALIDATE_DUMP) &&
> > +	    ctx->nlh->nlmsg_len < nlmsg_msg_size(ctx->hdrlen))
> >  		return -EINVAL;
> >  
> >  	attrs = genl_family_rcv_msg_attrs_parse(ctx->family, ctx->nlh, ctx->extack,  
> 
> especially since this actually changes things to *have* the attrs, but
> not have *validated* them, which feels a bit strange and error-prone in
> the future maybe?

Do you mean that we no longer populate op->maxattr / op->policy and
some op may be reading those? I don't see any family code looking at
info->op.policy / maxattr.

First thing genl_family_rcv_msg_attrs_parse() does is:

	if (!ops->maxattr)
		return NULL;

So whether we skip it or call it - no difference.