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tcp: eliminate negative reordering in tcp_clean_rtx_queue

PATCH In review Soheil Hassas Yeganeh 2 participants 2 messages May 15, 2017 – May 16, 2017

Subsystems (3)
Networking Network drivers TCP
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Soheil Hassas Yeganeh

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#0 lore raw

PATCH 1/1 tcp: eliminate negative reordering in tcp_clean_rtx_queue

From: Soheil Hassas Yeganeh <[email protected]>

tcp_ack() can call tcp_fragment() which may dededuct the value tp->fackets_out when MSS changes. When prior_fackets is larger than tp->fackets_out, tcp_clean_rtx_queue() can invoke tcp_update_reordering() with negative values. This results in absurd tp->reodering values higher than sysctl_tcp_max_reordering.

Note that tcp_update_reordering indeeds sets tp->reordering to min(sysctl_tcp_max_reordering, metric), but because the comparison is signed, a negative metric always wins.

Fixes c7caf8d3ed7a ("[TCP]: Fix reord detection due to snd_una covered holes")
Reported-by Rebecca Isaacs <[email protected]>
Signed-off-by Soheil Hassas Yeganeh <[email protected]>
Signed-off-by Neal Cardwell <[email protected]>
Signed-off-by Yuchung Cheng <[email protected]>
Signed-off-by Eric Dumazet <[email protected]>
---
 net/ipv4/tcp_input.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
net/ipv4/tcp_input.c +1 -1
index 9739962bfb3f..f27dff64e59e 100644
@@ -3190,7 +3190,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 			int delta;
 
 			/* Non-retransmitted hole got filled? That's reordering */
-			if (reord < prior_fackets)
+			if (reord < prior_fackets && reord <= tp->fackets_out)
 				tcp_update_reordering(sk, tp->fackets_out - reord, 0);
 
 			delta = tcp_is_fack(tp) ? pkts_acked :
Signature · 1 line
2.13.0.rc2.291.g57267f2277-goog
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#1 lore raw

From: Soheil Hassas Yeganeh <[email protected]>
Date: Mon, 15 May 2017 17:05:47 -0400

Quoted 13 lines

From: Soheil Hassas Yeganeh <[email protected]>

tcp_ack() can call tcp_fragment() which may dededuct the value tp->fackets_out when MSS changes. When prior_fackets is larger than tp->fackets_out, tcp_clean_rtx_queue() can invoke tcp_update_reordering() with negative values. This results in absurd tp->reodering values higher than sysctl_tcp_max_reordering.

Note that tcp_update_reordering indeeds sets tp->reordering to min(sysctl_tcp_max_reordering, metric), but because the comparison is signed, a negative metric always wins.

Quoted 6 lines
Fixes c7caf8d3ed7a ("[TCP]: Fix reord detection due to snd_una covered holes")
Reported-by Rebecca Isaacs <[email protected]>
Signed-off-by Soheil Hassas Yeganeh <[email protected]>
Signed-off-by Neal Cardwell <[email protected]>
Signed-off-by Yuchung Cheng <[email protected]>
Signed-off-by Eric Dumazet <[email protected]>

Applied and queued up for -stable, thanks.