From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: Re: [PATCH] netfilter: check the length of the data before dereferencing it Date: Sun, 1 Apr 2012 18:43:25 +0200 Message-ID: <20120401164325.GB10861@1984> References: <1333290170-26898-1-git-send-email-xiaosuo@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Patrick McHardy , "David S. Miller" , netfilter-devel@vger.kernel.org, netdev@vger.kernel.org To: Changli Gao Return-path: Content-Disposition: inline In-Reply-To: <1333290170-26898-1-git-send-email-xiaosuo@gmail.com> Sender: netfilter-devel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Sun, Apr 01, 2012 at 10:22:50PM +0800, Changli Gao wrote: > We should check the length of the data before dereferencing it when parsing > the TCP options. > > Signed-off-by: Changli Gao > --- > net/netfilter/nf_conntrack_proto_tcp.c | 4 ++++ > 1 file changed, 4 insertions(+) > diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c > index 361eade..9e446c5 100644 > --- a/net/netfilter/nf_conntrack_proto_tcp.c > +++ b/net/netfilter/nf_conntrack_proto_tcp.c > @@ -404,6 +404,8 @@ static void tcp_options(const struct sk_buff *skb, > length--; > continue; > default: > + if (length < 2) > + return; > opsize=*ptr++; > if (opsize < 2) /* "silly options" */ > return; length is always multiple of 4: int length = (tcph->doff*4) - sizeof(struct tcphdr);