From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932931Ab3HHBtL (ORCPT ); Wed, 7 Aug 2013 21:49:11 -0400 Received: from intranet.asianux.com ([58.214.24.6]:64338 "EHLO intranet.asianux.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757547Ab3HHBtK (ORCPT ); Wed, 7 Aug 2013 21:49:10 -0400 X-Spam-Score: -100.8 Message-ID: <5202F8D6.3000607@asianux.com> Date: Thu, 08 Aug 2013 09:48:06 +0800 From: Chen Gang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Andy Lutomirski CC: Oleg Nesterov , Michael Kerrisk , Kees Cook , Al Viro , holt@sgi.com, Andrew Morton , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/2] kernel/sys.c: return the current gid when error occurs References: <5200AD26.8070701@asianux.com> <5200AD67.1030109@asianux.com> <52015ADB.30408@mit.edu> <20130807162147.GA31460@redhat.com> <5202F4A3.5070603@asianux.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/08/2013 09:35 AM, Andy Lutomirski wrote: > On Wed, Aug 7, 2013 at 6:30 PM, Chen Gang wrote: >> On 08/08/2013 12:58 AM, Andy Lutomirski wrote: >>> On Wed, Aug 7, 2013 at 9:21 AM, Oleg Nesterov wrote: >>>> On 08/06, Andy Lutomirski wrote: >>>>> >>>>> I assume that what the man page means is that the return value is >>>>> whatever fsgid was prior to the call. On error, fsgid isn't changed, so >>>>> the return value is still "current". >>>> >>>> Probably... Still >>>> >>>> On success, the previous value of fsuid is returned. >>>> On error, the current value of fsuid is returned. >>>> >>>> looks confusing. sys_setfsuid() always returns the old value. >>>> >>>>> (FWIW, this behavior is awful and is probably the cause of a security >>>>> bug or three, since success and failure are indistinguishable. >>>> >>>> At least this all looks strange. >>>> >>>> I dunno if we can change this old behaviour. I won't be surprized >>>> if someone already uses setfsuid(-1) as getfsuid(). >>> >> >> Oh, really it is. >> >> Hmm... as a pair function, we need add getfsuid() too, if we do not add >> it, it will make negative effect with setfsuid(). >> >> Since it is a system call, we have to keep compitable. >> >> So in my opinion, better add getfsuid2()/setfsuid2() instead of current >> setfsuid() > > How about getfsuid() and setfsuid2()? > Hmm... I have 2 reasons, please check. 1st reason: I checked history (just like Kees Cook suggested), getfsuid() is mentioned before (you can google to find it), so need use getfsuid2() to bypass the history complex. And 2nd reason: getfsuid() seems more like the pair of setfsuid(), not for setfsuid2(). > --Andy > > Thanks. -- Chen Gang