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Commit bd090dfc authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric 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: default avatarDavid S. Miller <davem@davemloft.net>
parent bbc8d922

net/ipv4/tcp_input.c

+10 −5
Original line number Diff line number Diff line
@@ -5313,11 +5313,6 @@ 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
@@ -5552,6 +5547,11 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, 
	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. */
@@ -6130,6 +6130,11 @@ 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);