From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH] tcp: dont handle MTU reduction on LISTEN socket Date: Mon, 18 Mar 2013 10:01:28 -0700 Message-ID: <1363626088.29475.155.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev , dormando To: David Miller Return-path: Received: from mail-pb0-f49.google.com ([209.85.160.49]:60067 "EHLO mail-pb0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751891Ab3CRRBb (ORCPT ); Mon, 18 Mar 2013 13:01:31 -0400 Received: by mail-pb0-f49.google.com with SMTP id xa12so6525677pbc.22 for ; Mon, 18 Mar 2013 10:01:31 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet When an ICMP ICMP_FRAG_NEEDED (or ICMPV6_PKT_TOOBIG) message finds a LISTEN socket, and this socket is currently owned by the user, we set TCP_MTU_REDUCED_DEFERRED flag in listener tsq_flags. This is bad because if we clone the parent before it had a chance to clear the flag, the child inherits the tsq_flags value, and next tcp_release_cb() on the child will decrement sk_refcnt. Result is that we might free a live TCP socket, as reported by Dormando. IPv4: Attempt to release TCP socket in state 1 Fix this issue by testing sk_state against TCP_LISTEN early, so that we set TCP_MTU_REDUCED_DEFERRED on appropriate sockets (not a LISTEN one) This bug was introduced in commit 563d34d05786 (tcp: dont drop MTU reduction indications) Reported-by: dormando Signed-off-by: Eric Dumazet --- net/ipv4/tcp_ipv4.c | 14 +++++++------- net/ipv6/tcp_ipv6.c | 7 +++++++ 2 files changed, 14 insertions(+), 7 deletions(-) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 4a8ec45..d09203c 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -274,13 +274,6 @@ static void tcp_v4_mtu_reduced(struct sock *sk) struct inet_sock *inet = inet_sk(sk); u32 mtu = tcp_sk(sk)->mtu_info; - /* We are not interested in TCP_LISTEN and open_requests (SYN-ACKs - * send out by Linux are always <576bytes so they should go through - * unfragmented). - */ - if (sk->sk_state == TCP_LISTEN) - return; - dst = inet_csk_update_pmtu(sk, mtu); if (!dst) return; @@ -408,6 +401,13 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info) goto out; if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */ + /* We are not interested in TCP_LISTEN and open_requests + * (SYN-ACKs send out by Linux are always <576bytes so + * they should go through unfragmented). + */ + if (sk->sk_state == TCP_LISTEN) + goto out; + tp->mtu_info = info; if (!sock_owned_by_user(sk)) { tcp_v4_mtu_reduced(sk); diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 9b64600..f6d629f 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -389,6 +389,13 @@ static void tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt, } if (type == ICMPV6_PKT_TOOBIG) { + /* We are not interested in TCP_LISTEN and open_requests + * (SYN-ACKs send out by Linux are always <576bytes so + * they should go through unfragmented). + */ + if (sk->sk_state == TCP_LISTEN) + goto out; + tp->mtu_info = ntohl(info); if (!sock_owned_by_user(sk)) tcp_v6_mtu_reduced(sk);