From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [patch] net_sched: stack info leak in cbq_dump_wrr() Date: Tue, 30 Jul 2013 00:18:08 -0700 (PDT) Message-ID: <20130730.001808.1649128808672716753.davem@davemloft.net> References: <1375128751.2075.58.camel@joe-AO722> <20130730065509.GB29160@mwanda> <1375168352.2075.110.camel@joe-AO722> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: dan.carpenter@oracle.com, jhs@mojatatu.com, netdev@vger.kernel.org, kernel-janitors@vger.kernel.org To: joe@perches.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:58301 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753572Ab3G3HSJ (ORCPT ); Tue, 30 Jul 2013 03:18:09 -0400 In-Reply-To: <1375168352.2075.110.camel@joe-AO722> Sender: netdev-owner@vger.kernel.org List-ID: From: Joe Perches Date: Tue, 30 Jul 2013 00:12:32 -0700 > On Tue, 2013-07-30 at 09:55 +0300, Dan Carpenter wrote: >> On Mon, Jul 29, 2013 at 01:12:31PM -0700, Joe Perches wrote: >> > On Mon, 2013-07-29 at 23:01 +0300, Dan Carpenter wrote: >> > > On Mon, Jul 29, 2013 at 12:44:32PM -0700, Joe Perches wrote: >> > > > On Mon, 2013-07-29 at 22:36 +0300, Dan Carpenter wrote: >> > > > > opt.__reserved isn't cleared so we leak a byte of stack information. >> > > > [] >> > > > > diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c >> > > > [] >> > > > > @@ -1469,6 +1469,7 @@ static int cbq_dump_wrr(struct sk_buff *skb, struct cbq_class *cl) >> > > > > opt.allot = cl->allot; >> > > > > opt.priority = cl->priority + 1; >> > > > > opt.cpriority = cl->cpriority + 1; >> > > > > + opt.__reserved = 0; >> > > > > opt.weight = cl->weight; >> > > > > if (nla_put(skb, TCA_CBQ_WRROPT, sizeof(opt), &opt)) >> > > > > goto nla_put_failure; >> > > > >> > > > Alignment isn't guaranteed here so it'd >> > > > probably be better with a memset. >> > > > >> > > >> > > Hm... Which arches would align it differently? >> > >> > Hey Dan. >> > >> > None so far as I know, but what difference does it make >> > when it's a general correctness issue? >> > >> >> Because I would assume if these aren't aligned the same way we have >> far more serious problems than just this one case. It would change >> the user space API and break network protocols. > > > > I didn't say it was necessary to be done here, I said it > was a correctness issue. I still believe that's true. > > The nla_put here is by structure, the struct is unpacked, > and it's local to the arch, not a particular endian type. > > btw: to answer David's question, gcc 4.7 is smart enough > to elide resetting values when the struct is initialized > to 0 either with a memset or using {0}. Ok, I've just commited the following, thanks everyone. -------------------- >>From a0db856a95a29efb1c23db55c02d9f0ff4f0db48 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Tue, 30 Jul 2013 00:16:21 -0700 Subject: [PATCH] net_sched: Fix stack info leak in cbq_dump_wrr(). Make sure the reserved fields, and padding (if any), are fully initialized. Based upon a patch by Dan Carpenter and feedback from Joe Perches. Signed-off-by: David S. Miller --- net/sched/sch_cbq.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c index 71a5688..7a42c81 100644 --- a/net/sched/sch_cbq.c +++ b/net/sched/sch_cbq.c @@ -1465,6 +1465,7 @@ static int cbq_dump_wrr(struct sk_buff *skb, struct cbq_class *cl) unsigned char *b = skb_tail_pointer(skb); struct tc_cbq_wrropt opt; + memset(&opt, 0, sizeof(opt)); opt.flags = 0; opt.allot = cl->allot; opt.priority = cl->priority + 1; -- 1.7.11.7