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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>
This commit is contained in:
Eric Dumazet 2012-11-13 05:37:18 +00:00 committed by David S. Miller
parent bbc8d9228e
commit bd090dfc63
1 changed files with 10 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
net/ipv4/tcp_input.c
View File

@ -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);