From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27645C10F14 for ; Thu, 10 Oct 2019 09:13:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 087E42067B for ; Thu, 10 Oct 2019 09:13:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387761AbfJJJNu (ORCPT ); Thu, 10 Oct 2019 05:13:50 -0400 Received: from mx2.suse.de ([195.135.220.15]:43954 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1733250AbfJJJNu (ORCPT ); Thu, 10 Oct 2019 05:13:50 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 9B9B7B061; Thu, 10 Oct 2019 09:13:48 +0000 (UTC) Received: by unicorn.suse.cz (Postfix, from userid 1000) id 34DE4E378C; Thu, 10 Oct 2019 11:13:47 +0200 (CEST) Date: Thu, 10 Oct 2019 11:13:47 +0200 From: Michal Kubecek To: Jiri Pirko Cc: "David S. Miller" , Jiri Pirko , Johannes Berg , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] genetlink: do not parse attributes for families with zero maxattr Message-ID: <20191010091347.GA22163@unicorn.suse.cz> References: <20191009164432.AD5D1E3785@unicorn.suse.cz> <20191010083958.GD2223@nanopsycho> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191010083958.GD2223@nanopsycho> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 10, 2019 at 10:39:58AM +0200, Jiri Pirko wrote: > Wed, Oct 09, 2019 at 06:44:32PM CEST, mkubecek@suse.cz wrote: > >Commit c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing > >to a separate function") moved attribute buffer allocation and attribute > >parsing from genl_family_rcv_msg_doit() into a separate function > >genl_family_rcv_msg_attrs_parse() which, unlike the previous code, calls > >__nlmsg_parse() even if family->maxattr is 0 (i.e. the family does its own > >parsing). The parser error is ignored and does not propagate out of > >genl_family_rcv_msg_attrs_parse() but an error message ("Unknown attribute > >type") is set in extack and if further processing generates no error or > >warning, it stays there and is interpreted as a warning by userspace. > > > >Dumpit requests are not affected as genl_family_rcv_msg_dumpit() bypasses > >the call of genl_family_rcv_msg_doit() if family->maxattr is zero. Do the > >same also in genl_family_rcv_msg_doit(). > > This is the original code before the changes: > > if (ops->doit == NULL) > return -EOPNOTSUPP; > > if (family->maxattr && family->parallel_ops) { > attrbuf = kmalloc_array(family->maxattr + 1, > sizeof(struct nlattr *), > GFP_KERNEL); > if (attrbuf == NULL) > return -ENOMEM; > } else > attrbuf = family->attrbuf; > > if (attrbuf) { > enum netlink_validation validate = NL_VALIDATE_STRICT; > > if (ops->validate & GENL_DONT_VALIDATE_STRICT) > validate = NL_VALIDATE_LIBERAL; > > err = __nlmsg_parse(nlh, hdrlen, attrbuf, family->maxattr, > family->policy, validate, extack); > if (err < 0) > goto out; > } > > Looks like the __nlmsg_parse() is called no matter if maxattr if 0 or > not. It is only considered for allocation of attrbuf. This is in-sync > with the current code. If family->maxattr is 0, genl_register_family() sets family->attrbuf to NULL so that attrbuf is also NULL and the whole "if (attrbuf) { ... }" block is not executed. Michal