From b37593c406b332aec4154e0e5e9572c24c6bcd7e Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Fri, 22 Jan 2016 01:39:43 +0100 Subject: [PATCH] pptp: fix illegal memory access caused by multiple bind()s 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(-) diff --git a/drivers/net/ppp/pptp.c b/drivers/net/ppp/pptp.c index 165ee14825b8..cefb47334ac7 100644 --- a/drivers/net/ppp/pptp.c +++ b/drivers/net/ppp/pptp.c @@ -131,24 +131,27 @@ static int lookup_chan_dst(u16 call_id, __be32 d_addr) 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 sockaddr *uservaddr, 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, struct sockaddr *uservaddr, 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 *sock, struct sockaddr *uservaddr, } opt->dst_addr = sp->sa_addr.pptp; - sk->sk_state = PPPOX_CONNECTED; + sk->sk_state |= PPPOX_CONNECTED; end: release_sock(sk); -- 2.39.2