From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH] tc: Fix unitialized kernel memory leak Date: Wed, 2 Sep 2009 23:34:10 -0700 Message-ID: <20090902233410.19f0705b@nehalam> References: <4A9E67A9.7090205@gmail.com> <20090902120540.34e2a198@nehalam> <20090902.225108.168195116.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org To: David Miller Return-path: Received: from mail.vyatta.com ([76.74.103.46]:56151 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754519AbZICGeN (ORCPT ); Thu, 3 Sep 2009 02:34:13 -0400 In-Reply-To: <20090902.225108.168195116.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 02 Sep 2009 22:51:08 -0700 (PDT) David Miller wrote: > From: Stephen Hemminger > Date: Wed, 2 Sep 2009 12:05:40 -0700 > > > On Wed, 02 Sep 2009 14:40:09 +0200 > > Eric Dumazet wrote: > > > >> Three bytes of uninitialized kernel memory are currently leaked to user > >> > >> Signed-off-by: Eric Dumazet > >> --- > >> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c > >> index 24d17ce..fdb694e 100644 > >> --- a/net/sched/sch_api.c > >> +++ b/net/sched/sch_api.c > >> @@ -1456,6 +1456,8 @@ static int tc_fill_tclass(struct sk_buff *skb, struct Qdisc *q, > >> nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*tcm), flags); > >> tcm = NLMSG_DATA(nlh); > >> tcm->tcm_family = AF_UNSPEC; > >> + tcm->tcm__pad1 = 0; > >> + tcm->tcm__pad2 = 0; > >> tcm->tcm_ifindex = qdisc_dev(q)->ifindex; > >> tcm->tcm_parent = q->handle; > >> tcm->tcm_handle = q->handle; > > > > Perhaps __nlmsg_put should just always call memset() for the whole > > added chunk. It is not like it is critical path in any way, and > > avoid any of this possible class of errors. > > Doing it in __nlmsg_put would effect a lot of code paths. I don't > think you can say with certainty that it won't matter, tree wide. > > What about things like the netfilter conntrack event monitor? Doesn't > that emit hundreds of thousands of events per second on a busy > firewall? I doubt it would make a noticeable performance difference because the first memset would incur the cache penalty of the write (if any) and later update of fields would be cached. --