From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756266AbYGLDwS (ORCPT ); Fri, 11 Jul 2008 23:52:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753326AbYGLDwG (ORCPT ); Fri, 11 Jul 2008 23:52:06 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:50329 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752535AbYGLDwE (ORCPT ); Fri, 11 Jul 2008 23:52:04 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: "Stoyan Gaydarov" Cc: "Denis V. Lunev" , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, "Alexey Dobriyan" , "Eric W. Biederman" , "David S. Miller" References: <1209467538.29647.11.camel@iris.sw.ru> <1209467602-20001-9-git-send-email-den@openvz.org> <6d291e080807112012r7ae44318oc41366b83d484b7f@mail.gmail.com> Date: Fri, 11 Jul 2008 20:42:51 -0700 In-Reply-To: <6d291e080807112012r7ae44318oc41366b83d484b7f@mail.gmail.com> (Stoyan Gaydarov's message of "Fri, 11 Jul 2008 22:12:30 -0500") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-SA-Exim-Connect-IP: 24.130.11.59 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-DCC: XMission; sa02 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;"Stoyan Gaydarov" X-Spam-Relay-Country: X-Spam-Report: * -1.8 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0024] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa02 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 XM_SPF_Neutral SPF-Neutral Subject: Re: [PATCH 9/12] ipv4: assign PDE->data before gluing PDE into /proc tree X-SA-Exim-Version: 4.2 (built Thu, 03 Mar 2005 10:44:12 +0100) X-SA-Exim-Scanned: Yes (on mgr1.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Stoyan Gaydarov" writes: > First off, sorry to bring such an old email back but I can seem to get > a bad feeling when looking back over it. > > On Tue, Apr 29, 2008 at 6:13 AM, Denis V. Lunev wrote: >> The check for PDE->data != NULL becomes useless after the replacement >> of proc_net_fops_create with proc_create_data. >> >> Signed-off-by: Denis V. Lunev >> Cc: Alexey Dobriyan >> Cc: Eric W. Biederman >> Cc: David S. Miller >> --- >> net/ipv4/tcp_ipv4.c | 10 +++------- >> net/ipv4/udp.c | 7 +++---- >> 2 files changed, 6 insertions(+), 11 deletions(-) >> >> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c >> index 7766151..4d97b28 100644 >> --- a/net/ipv4/tcp_ipv4.c >> +++ b/net/ipv4/tcp_ipv4.c >> @@ -2214,9 +2214,6 @@ static int tcp_seq_open(struct inode *inode, struct file > *file) >> struct tcp_iter_state *s; >> int err; >> >> - if (unlikely(afinfo == NULL)) >> - return -EINVAL; > I think that this check needs to stay in some form, reason below. >> - >> err = seq_open_net(inode, file, &afinfo->seq_ops, >> sizeof(struct tcp_iter_state)); >> if (err < 0) >> @@ -2241,10 +2238,9 @@ int tcp_proc_register(struct net *net, struct > tcp_seq_afinfo *afinfo) >> afinfo->seq_ops.next = tcp_seq_next; >> afinfo->seq_ops.stop = tcp_seq_stop; >> >> - p = proc_net_fops_create(net, afinfo->name, S_IRUGO, &afinfo->seq_fops); >> - if (p) >> - p->data = afinfo; >> - else >> + p = proc_create_data(afinfo->name, S_IRUGO, net->proc_net, > > When you try to pass in afinfo->name (and also the seq_fops) you are > assuming that afinfo is not null meaning in the unlikely(as shown > above) even that it is null you get a very bad null pointer problem. > If I am just way off do let me know because this just seams to me like > a bad idea. This is also still present in 2.6.26-rc9. It appears you are getting things confused. The original window is that tcp_seq_open (which is what get called when you open the proc file) had a small race that p->data could be read before it was set. With proc_create_data that race was closed. You are saying that it is a problem for tcp_seq_open to be passed a NULL afinfo. It is. That has nothing to do with the original race (as that is a very different part of the code). Feel free to audit all of the callers if you like. That problem however is not subtle or racy. So I see nothing wrong with this patch unless you can find a problem with proc_create_data. Eric