This is a note to let you know that I've just added the patch titled
tcp: do not mangle skb->cb[] in tcp_make_synack()
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tcp-do-not-mangle-skb-cb-in-tcp_make_synack.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Tue Nov 21 15:28:16 CET 2017
From: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Thu, 2 Nov 2017 12:30:25 -0700
Subject: tcp: do not mangle skb->cb[] in tcp_make_synack()
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit 3b11775033dc87c3d161996c54507b15ba26414a ]
Christoph Paasch sent a patch to address the following issue :
tcp_make_synack() is leaving some TCP private info in skb->cb[],
then send the packet by other means than tcp_transmit_skb()
tcp_transmit_skb() makes sure to clear skb->cb[] to not confuse
IPv4/IPV6 stacks, but we have no such cleanup for SYNACK.
tcp_make_synack() should not use tcp_init_nondata_skb() :
tcp_init_nondata_skb() really should be limited to skbs put in write/rtx
queues (the ones that are only sent via tcp_transmit_skb())
This patch fixes the issue and should even save few cpu cycles ;)
Fixes: 971f10eca186 ("tcp: better TCP_SKB_CB layout to reduce cache line misses")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reported-by: Christoph Paasch <cpaasch@xxxxxxxxx>
Reviewed-by: Christoph Paasch <cpaasch@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/tcp_output.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3018,13 +3018,8 @@ struct sk_buff *tcp_make_synack(const st
tcp_ecn_make_synack(req, th);
th->source = htons(ireq->ir_num);
th->dest = ireq->ir_rmt_port;
- /* Setting of flags are superfluous here for callers (and ECE is
- * not even correctly set)
- */
- tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
- TCPHDR_SYN | TCPHDR_ACK);
-
- th->seq = htonl(TCP_SKB_CB(skb)->seq);
+ skb->ip_summed = CHECKSUM_PARTIAL;
+ th->seq = htonl(tcp_rsk(req)->snt_isn);
/* XXX data is queued and acked as is. No buffer/window check */
th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
Patches currently in stable-queue which might be from edumazet@xxxxxxxxxx are
queue-4.4/tcp-do-not-mangle-skb-cb-in-tcp_make_synack.patch