Patch "tcp md5sig: Use skb's saddr when replying to an incoming segment" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

tcp md5sig: Use skb's saddr when replying to an incoming segment

to the 4.14-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-md5sig-use-skb-s-saddr-when-replying-to-an-incoming-segment.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Christoph Paasch <[email protected]>
Date: Mon, 11 Dec 2017 00:05:46 -0800
Subject: tcp md5sig: Use skb's saddr when replying to an incoming segment

From: Christoph Paasch <[email protected]>

[ Upstream commit 30791ac41927ebd3e75486f9504b6d2280463bf0 ]

The MD5-key that belongs to a connection is identified by the peer's IP-address. When we are in tcp_v4(6)_reqsk_send_ack(), we are replying to an incoming segment from tcp_check_req() that failed the seq-number checks.

Thus, to find the correct key, we need to use the skb's saddr and not the daddr.

This bug seems to have been there since quite a while, but probably got unnoticed because the consequences are not catastrophic. We will call tcp_v4_reqsk_send_ack only to send a challenge-ACK back to the peer, thus the connection doesn't really fail.

---
 net/ipv4/tcp_ipv4.c |    2 +-
 net/ipv6/tcp_ipv6.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

@@ -844,7 +844,7 @@ static void tcp_v4_reqsk_send_ack(const
 			tcp_time_stamp_raw() + tcp_rsk(req)->ts_off,
 			req->ts_recent,
 			0,
-			tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&ip_hdr(skb)->daddr,
+			tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&ip_hdr(skb)->saddr,
 					  AF_INET),
 			inet_rsk(req)->no_srccheck ? IP_REPLY_ARG_NOSRCCHECK : 0,
 			ip_hdr(skb)->tos);

@@ -988,7 +988,7 @@ static void tcp_v6_reqsk_send_ack(const
 			req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
 			tcp_time_stamp_raw() + tcp_rsk(req)->ts_off,
 			req->ts_recent, sk->sk_bound_dev_if,
-			tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->daddr),
+			tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->saddr),
 			0, 0);
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/tcp-md5sig-use-skb-s-saddr-when-replying-to-an-incoming-segment.patch