From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH v2] tcp: tcp_replace_ts_recent() should not be called from tcp_validate_incoming() Date: Tue, 13 Nov 2012 07:37:18 -0800 Message-ID: <1352821038.6185.38.camel@edumazet-glaptop> References: <1352793951.6185.28.camel@edumazet-glaptop> <87k3tp6783.fsf@silenus.orebokech.com> <1352813332.6185.29.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev , Neal Cardwell , Yuchung Cheng , Nandita Dukkipati , "H.K. Jerry Chu" To: Romain Francoise , David Miller Return-path: Received: from mail-ie0-f174.google.com ([209.85.223.174]:37416 "EHLO mail-ie0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752317Ab2KMPhV (ORCPT ); Tue, 13 Nov 2012 10:37:21 -0500 Received: by mail-ie0-f174.google.com with SMTP id k13so10874974iea.19 for ; Tue, 13 Nov 2012 07:37:21 -0800 (PST) In-Reply-To: <1352813332.6185.29.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet We added support for RFC 5961 in latest kernels but TCP fails to perform exhaustive check of ACK sequence. We can update our view of peer tsval from a frame that is later discarded by tcp_ack() This makes timestamps enabled sessions vulnerable to injection of a high tsval : peers start an ACK storm, since the victim sends a dupack each time it receives an ACK from the other peer. As tcp_validate_incoming() is called before tcp_ack(), we should not peform tcp_replace_ts_recent() from it, and let callers do it at the right time. Signed-off-by: Eric Dumazet Cc: Neal Cardwell Cc: Yuchung Cheng Cc: Nandita Dukkipati Cc: H.K. Jerry Chu Cc: Romain Francoise --- v2: fix a typo in RFC number, as pointed out by Romain Francoise net/ipv4/tcp_input.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 7839d51..fc67831 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5320,11 +5320,6 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, goto discard; } - /* ts_recent update must be made after we are sure that the packet - * is in window. - */ - tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); - /* step 3: check security and precedence [ignored] */ /* step 4: Check for a SYN @@ -5559,6 +5554,11 @@ step5: if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0) goto discard; + /* ts_recent update must be made after we are sure that the packet + * is in window. + */ + tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); + tcp_rcv_rtt_measure_ts(sk, skb); /* Process urgent data. */ @@ -6137,6 +6137,11 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, } else goto discard; + /* ts_recent update must be made after we are sure that the packet + * is in window. + */ + tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); + /* step 6: check the URG bit */ tcp_urg(sk, skb, th);