From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932150AbcBWVqM (ORCPT ); Tue, 23 Feb 2016 16:46:12 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41795 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755677AbcBWVpD (ORCPT ); Tue, 23 Feb 2016 16:45:03 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Dmitry Kozlov" , "Dave Jones" , "Dmitry Vyukov" , "Sasha Levin" , "David S. Miller" , "Hannes Frederic Sowa" Date: Tue, 23 Feb 2016 21:42:03 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 09/67] pptp: fix illegal memory access caused by multiple bind()s In-Reply-To: X-SA-Exim-Connect-IP: 92.40.248.141 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.78-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Hannes Frederic Sowa commit 9a368aff9cb370298fa02feeffa861f2db497c18 upstream. Several times already this has been reported as kasan reports caused by syzkaller and trinity and people always looked at RCU races, but it is much more simple. :) In case we bind a pptp socket multiple times, we simply add it to the callid_sock list but don't remove the old binding. Thus the old socket stays in the bucket with unused call_id indexes and doesn't get cleaned up. This causes various forms of kasan reports which were hard to pinpoint. Simply don't allow multiple binds and correct error handling in pptp_bind. Also keep sk_state bits in place in pptp_connect. Fixes: 00959ade36acad ("PPTP: PPP over IPv4 (Point-to-Point Tunneling Protocol)") Cc: Dmitry Kozlov Cc: Sasha Levin Cc: Dmitry Vyukov Reported-by: Dmitry Vyukov Cc: Dave Jones Reported-by: Dave Jones Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- drivers/net/ppp/pptp.c | 34 ++++++++++++++++++++++++---------- 1 file changed, 24 insertions(+), 10 deletions(-) --- a/drivers/net/ppp/pptp.c +++ b/drivers/net/ppp/pptp.c @@ -131,24 +131,27 @@ static int lookup_chan_dst(u16 call_id, return i < MAX_CALLID; } -static int add_chan(struct pppox_sock *sock) +static int add_chan(struct pppox_sock *sock, + struct pptp_addr *sa) { static int call_id; spin_lock(&chan_lock); - if (!sock->proto.pptp.src_addr.call_id) { + if (!sa->call_id) { call_id = find_next_zero_bit(callid_bitmap, MAX_CALLID, call_id + 1); if (call_id == MAX_CALLID) { call_id = find_next_zero_bit(callid_bitmap, MAX_CALLID, 1); if (call_id == MAX_CALLID) goto out_err; } - sock->proto.pptp.src_addr.call_id = call_id; - } else if (test_bit(sock->proto.pptp.src_addr.call_id, callid_bitmap)) + sa->call_id = call_id; + } else if (test_bit(sa->call_id, callid_bitmap)) { goto out_err; + } - set_bit(sock->proto.pptp.src_addr.call_id, callid_bitmap); - rcu_assign_pointer(callid_sock[sock->proto.pptp.src_addr.call_id], sock); + sock->proto.pptp.src_addr = *sa; + set_bit(sa->call_id, callid_bitmap); + rcu_assign_pointer(callid_sock[sa->call_id], sock); spin_unlock(&chan_lock); return 0; @@ -417,7 +420,6 @@ static int pptp_bind(struct socket *sock struct sock *sk = sock->sk; struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr; struct pppox_sock *po = pppox_sk(sk); - struct pptp_opt *opt = &po->proto.pptp; int error = 0; if (sockaddr_len < sizeof(struct sockaddr_pppox)) @@ -425,10 +427,22 @@ static int pptp_bind(struct socket *sock lock_sock(sk); - opt->src_addr = sp->sa_addr.pptp; - if (add_chan(po)) + if (sk->sk_state & PPPOX_DEAD) { + error = -EALREADY; + goto out; + } + + if (sk->sk_state & PPPOX_BOUND) { error = -EBUSY; + goto out; + } + + if (add_chan(po, &sp->sa_addr.pptp)) + error = -EBUSY; + else + sk->sk_state |= PPPOX_BOUND; +out: release_sock(sk); return error; } @@ -499,7 +513,7 @@ static int pptp_connect(struct socket *s } opt->dst_addr = sp->sa_addr.pptp; - sk->sk_state = PPPOX_CONNECTED; + sk->sk_state |= PPPOX_CONNECTED; end: release_sock(sk);