From patchwork Mon Nov 12 12:04:26 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luis Henriques X-Patchwork-Id: 198378 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from chlorine.canonical.com (chlorine.canonical.com [91.189.94.204]) by ozlabs.org (Postfix) with ESMTP id 7EC482C0086 for ; Mon, 12 Nov 2012 23:04:41 +1100 (EST) Received: from localhost ([127.0.0.1] helo=chlorine.canonical.com) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1TXskg-00047I-SO; Mon, 12 Nov 2012 12:04:30 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1TXske-00046p-2W for kernel-team@lists.ubuntu.com; Mon, 12 Nov 2012 12:04:28 +0000 Received: from av2-84-91-225-41.netvisao.pt ([84.91.225.41] helo=localhost) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1TXskd-0008N1-Tb for kernel-team@lists.ubuntu.com; Mon, 12 Nov 2012 12:04:28 +0000 From: Luis Henriques To: kernel-team@lists.ubuntu.com Subject: [hardy, lucid, oneiric, precise, quantal CVE 1/1] net: fix divide by zero in tcp algorithm illinois Date: Mon, 12 Nov 2012 12:04:26 +0000 Message-Id: <1352721866-16193-1-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.7.10.4 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.13 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: kernel-team-bounces@lists.ubuntu.com Errors-To: kernel-team-bounces@lists.ubuntu.com From: Jesper Dangaard Brouer BugLink: http://bugs.launchpad.net/bugs/1077091 Reading TCP stats when using TCP Illinois congestion control algorithm can cause a divide by zero kernel oops. The division by zero occur in tcp_illinois_info() at: do_div(t, ca->cnt_rtt); where ca->cnt_rtt can become zero (when rtt_reset is called) Steps to Reproduce: 1. Register tcp_illinois: # sysctl -w net.ipv4.tcp_congestion_control=illinois 2. Monitor internal TCP information via command "ss -i" # watch -d ss -i 3. Establish new TCP conn to machine Either it fails at the initial conn, or else it needs to wait for a loss or a reset. This is only related to reading stats. The function avg_delay() also performs the same divide, but is guarded with a (ca->cnt_rtt > 0) at its calling point in update_params(). Thus, simply fix tcp_illinois_info(). Function tcp_illinois_info() / get_info() is called without socket lock. Thus, eliminate any race condition on ca->cnt_rtt by using a local stack variable. Simply reuse info.tcpv_rttcnt, as its already set to ca->cnt_rtt. Function avg_delay() is not affected by this race condition, as its called with the socket lock. Cc: Petr Matousek Signed-off-by: Jesper Dangaard Brouer Acked-by: Eric Dumazet Acked-by: Stephen Hemminger Signed-off-by: David S. Miller (cherry picked from commit 8f363b77ee4fbf7c3bbcf5ec2c5ca482d396d664) CVE-2012-4565 Signed-off-by: Luis Henriques Acked-by: Andy Whitcroft --- net/ipv4/tcp_illinois.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c index 5aa5f54..f2c2ff0 100644 --- a/net/ipv4/tcp_illinois.c +++ b/net/ipv4/tcp_illinois.c @@ -314,11 +314,13 @@ static void tcp_illinois_info(struct sock *sk, u32 ext, .tcpv_rttcnt = ca->cnt_rtt, .tcpv_minrtt = ca->base_rtt, }; - u64 t = ca->sum_rtt; - do_div(t, ca->cnt_rtt); - info.tcpv_rtt = t; + if (info.tcpv_rttcnt > 0) { + u64 t = ca->sum_rtt; + do_div(t, info.tcpv_rttcnt); + info.tcpv_rtt = t; + } nla_put(skb, INET_DIAG_VEGASINFO, sizeof(info), &info); } }