tcp: tcp_replace_ts_recent() should not be called from tcp_validate_incoming()
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 <edumazet@google.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Nandita Dukkipati <nanditad@google.com> Cc: H.K. Jerry Chu <hkchu@google.com> Cc: Romain Francoise <romain@orebokech.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -5313,11 +5313,6 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
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goto discard;
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}
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/* ts_recent update must be made after we are sure that the packet
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* is in window.
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*/
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tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
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/* step 3: check security and precedence [ignored] */
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/* step 4: Check for a SYN
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@ -5552,6 +5547,11 @@ step5:
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if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0)
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goto discard;
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/* ts_recent update must be made after we are sure that the packet
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* is in window.
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*/
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tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
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tcp_rcv_rtt_measure_ts(sk, skb);
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/* Process urgent data. */
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@ -6130,6 +6130,11 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
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} else
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goto discard;
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/* ts_recent update must be made after we are sure that the packet
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* is in window.
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*/
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tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
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/* step 6: check the URG bit */
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tcp_urg(sk, skb, th);
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