Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751785Ab0KGLhj (ORCPT ); Sun, 7 Nov 2010 06:37:39 -0500 Received: from mx01.sz.bfs.de ([194.94.69.103]:14323 "EHLO mx01.sz.bfs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751540Ab0KGLhh (ORCPT ); Sun, 7 Nov 2010 06:37:37 -0500 Message-ID: <4CD68F7E.5050407@bfs.de> Date: Sun, 07 Nov 2010 12:37:34 +0100 From: walter harms Reply-To: wharms@bfs.de User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; de; rv:1.9.1.14) Gecko/20101013 SUSE/3.0.9 Thunderbird/3.0.9 MIME-Version: 1.0 To: Vasiliy Kulikov CC: kernel-janitors@vger.kernel.org, "David S. Miller" , Jiri Pirko , Eric Dumazet , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] net: packet: fix information leak to userland References: <1288545028-16436-1-git-send-email-segooon@gmail.com> <4CCE84E2.9050801@bfs.de> <20101106143911.GA17428@albatros> In-Reply-To: <20101106143911.GA17428@albatros> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2776 Lines: 85 Am 06.11.2010 15:39, schrieb Vasiliy Kulikov: > On Mon, Nov 01, 2010 at 10:14 +0100, walter harms wrote: >> >> >> Vasiliy Kulikov schrieb: >>> packet_getname_spkt() doesn't initialize all members of sa_data field of >>> sockaddr struct if strlen(dev->name) < 13. This structure is then copied >>> to userland. It leads to leaking of contents of kernel stack memory. >>> We have to fully fill sa_data with strncpy() instead of strlcpy(). >>> >>> The same with packet_getname(): it doesn't initialize sll_pkttype field of >>> sockaddr_ll. Set it to zero. >>> >>> Signed-off-by: Vasiliy Kulikov >>> --- >>> net/packet/af_packet.c | 3 ++- >>> 1 files changed, 2 insertions(+), 1 deletions(-) >>> >>> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c >>> index 3616f27..0856a13 100644 >>> --- a/net/packet/af_packet.c >>> +++ b/net/packet/af_packet.c >>> @@ -1719,7 +1719,7 @@ static int packet_getname_spkt(struct socket *sock, struct sockaddr *uaddr, >>> rcu_read_lock(); >>> dev = dev_get_by_index_rcu(sock_net(sk), pkt_sk(sk)->ifindex); >>> if (dev) >>> - strlcpy(uaddr->sa_data, dev->name, 15); >>> + strncpy(uaddr->sa_data, dev->name, 14); >>> else >>> memset(uaddr->sa_data, 0, 14); >> >> if i understand the code correcly the max size for dev->name is IFNAMSIZ. > > For dev->name - IFNAMSIZ, for uaddr->sa_data - 14. > did not notice, since uaddr->sa_data should take dev->name this does no look very clever. How is the size of sa_data defined ? Would it hurt when some uses IFNAMSIZ here ? Perhaps someone who know more about the network stack can figure out what is actualy done with uaddr->sa_data. looks like a can of worms. In packet_bind_spkt() they will copy a char[15], obviously it is a real problem. re, wh >> You can simply that part: >> >> memset(uaddr->sa_data, 0, IFNAMSIZ); >> dev = dev_get_by_index_rcu(sock_net(sk), pkt_sk(sk)->ifindex); >> if (dev) >> strlcpy(uaddr->sa_data, dev->name, IFNAMSIZ); > > This will overflow uaddr->sa_data. Also I don't see any difficulty to > fill the array only once. > >> you should send that as separate patch. >> re, >> wh >> >> >>> rcu_read_unlock(); >>> @@ -1742,6 +1742,7 @@ static int packet_getname(struct socket *sock, struct sockaddr *uaddr, >>> sll->sll_family = AF_PACKET; >>> sll->sll_ifindex = po->ifindex; >>> sll->sll_protocol = po->num; >>> + sll->sll_pkttype = 0; >>> rcu_read_lock(); >>> dev = dev_get_by_index_rcu(sock_net(sk), po->ifindex); >>> if (dev) { > > Thanks, > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/