[PATCH net] tcp: call tcp_rate_skb_sent() when retransmit with unaligned skb->data

[PATCH net] tcp: call tcp_rate_skb_sent() when retransmit with unaligned skb->data

[Yousuk Seung]

Current implementation calls tcp_rate_skb_sent() when tcp_transmit_skb()
is called when it clones skb only. Not calling tcp_rate_skb_sent() is OK
for all such code paths except from __tcp_retransmit_skb() which happens
when skb->data address is not aligned. This may rarely happen e.g. when
small amount of data is sent initially and the receiver partially acks
odd number of bytes for some reason, possibly malicious.

Signed-off-by: Yousuk Seung <ysseung@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp_output.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 973befc36fd4..1151870018e3 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2843,8 +2843,10 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
 		nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
 		err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
 			     -ENOBUFS;
-		if (!err)
+		if (!err) {
 			skb->skb_mstamp = tp->tcp_mstamp;
+			tcp_rate_skb_sent(sk, skb);
+		}
 	} else {
 		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
 	}
-- 
2.15.0.rc0.271.g36b669edcc-goog

Re: [PATCH net] tcp: call tcp_rate_skb_sent() when retransmit with unaligned skb->data

[David Miller]

From: Yousuk Seung <ysseung@google.com>
Date: Tue, 24 Oct 2017 16:44:42 -0700

> Current implementation calls tcp_rate_skb_sent() when tcp_transmit_skb()
> is called when it clones skb only. Not calling tcp_rate_skb_sent() is OK
> for all such code paths except from __tcp_retransmit_skb() which happens
> when skb->data address is not aligned. This may rarely happen e.g. when
> small amount of data is sent initially and the receiver partially acks
> odd number of bytes for some reason, possibly malicious.
> 
> Signed-off-by: Yousuk Seung <ysseung@google.com>
> Signed-off-by: Neal Cardwell <ncardwell@google.com>
> Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
> Acked-by: Eric Dumazet <edumazet@google.com>

This doesn't apply to any of m trees.