linux-kernel - [ 61/66] tcp: fix for zero packets_in

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20130217225008.708037902@decadent.org.uk>
Date:	Sun, 17 Feb 2013 22:51:02 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org,
	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>,
	Eric Dumazet <edumazet@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 61/66] tcp: fix for zero packets_in_flight was too broad

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>

[ Upstream commit 6731d2095bd4aef18027c72ef845ab1087c3ba63 ]

There are transients during normal FRTO procedure during which
the packets_in_flight can go to zero between write_queue state
updates and firing the resulting segments out. As FRTO processing
occurs during that window the check must be more precise to
not match "spuriously" :-). More specificly, e.g., when
packets_in_flight is zero but FLAG_DATA_ACKED is true the problematic
branch that set cwnd into zero would not be taken and new segments
might be sent out later.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
Tested-by: Eric Dumazet <edumazet@...gle.com>
Acked-by: Neal Cardwell <ncardwell@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/ipv4/tcp_input.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 308b5b4..e865ed1 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3635,8 +3635,7 @@ static int tcp_process_frto(struct sock *sk, int flag)
 	    ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED)))
 		tp->undo_marker = 0;
 
-	if (!before(tp->snd_una, tp->frto_highmark) ||
-	    !tcp_packets_in_flight(tp)) {
+	if (!before(tp->snd_una, tp->frto_highmark)) {
 		tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag);
 		return 1;
 	}
@@ -3656,6 +3655,11 @@ static int tcp_process_frto(struct sock *sk, int flag)
 		}
 	} else {
 		if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) {
+			if (!tcp_packets_in_flight(tp)) {
+				tcp_enter_frto_loss(sk, 2, flag);
+				return true;
+			}
+
 			/* Prevent sending of new data. */
 			tp->snd_cwnd = min(tp->snd_cwnd,
 					   tcp_packets_in_flight(tp));


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/