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

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Date:   Wed, 19 Oct 2022 21:33:43 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Jakub Kicinski <kuba@...nel.org>
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, 2022-10-19 at 12:20 -0700, Jakub Kicinski wrote:
> 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.
> 

Oh. I missed that, ok, thanks for clearing that up!

johannes