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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 C7F2EECDE44 for ; Wed, 24 Oct 2018 16:33:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9AAA22075D for ; Wed, 24 Oct 2018 16:33:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9AAA22075D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=1wt.eu Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726839AbeJYBBx (ORCPT ); Wed, 24 Oct 2018 21:01:53 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:35490 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726433AbeJYBBx (ORCPT ); Wed, 24 Oct 2018 21:01:53 -0400 Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id w9OGWUTi025385; Wed, 24 Oct 2018 18:32:30 +0200 Date: Wed, 24 Oct 2018 18:32:30 +0200 From: Willy Tarreau To: Joe Perches Cc: Wang Hai , edumazet@google.com, davem@davemloft.net, kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Change judgment len position Message-ID: <20181024163230.GA25382@1wt.eu> References: <20181024154729.5312-1-wanghaifine@gmail.com> <20181024155739.GA25314@1wt.eu> <60f08664db5751949ddfb34666bfda77f99682f1.camel@perches.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <60f08664db5751949ddfb34666bfda77f99682f1.camel@perches.com> User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 24, 2018 at 09:23:19AM -0700, Joe Perches wrote: > On Wed, 2018-10-24 at 17:57 +0200, Willy Tarreau wrote: > > On Wed, Oct 24, 2018 at 11:47:29PM +0800, Wang Hai wrote: > > > To determine whether len is less than zero, it should be put before > > > the function min_t, because the return value of min_t is not likely > > > to be less than zero. > > > > Huh? First, the <0 test is made on "len", not "min_t", so it still > > is signed. Second, you're in fact completely removing the test here, > > look : > > > > > struct net *net = sock_net(sk); > > > int val, len; > > > > > > + len = min_t(unsigned int, len, sizeof(int)); > > > + > > > > len is used uninitialized here, so the result is undefined. > > > > > if (get_user(len, optlen)) > > > return -EFAULT; > > > > Then it gets overridden by get_user() > > > > > - len = min_t(unsigned int, len, sizeof(int)); > > > - > > > > Then its positive values are not bounded anymore since you moved the test. > > Not quite. > > Problem here is negative values are tested as > large positive values and limited to 4 > > ie: > ien len = -1, > len = min_t(unsigned int, len, sizeof(int)); > > len is now 4 > > > > if (len < 0) > > > return -EINVAL; > > So this test len < 0 could be moved up above min_t It could indeed, or we could also have min_t() done on an int instead of an unsigned int and this would avoid the need to shuffle the code around and open a huge hole like this one. Willy