netdev - [RFC 5/5] net/tcp-md5: Don't send ACK if key (dis)appears

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Message-Id: <20230509221608.2569333-6-dima@arista.com>
Date: Tue,  9 May 2023 23:16:08 +0100
From: Dmitry Safonov <dima@...sta.com>
To: linux-kernel@...r.kernel.org,
	David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Jakub Kicinski <kuba@...nel.org>,
	"David S. Miller" <davem@...emloft.net>
Cc: Dmitry Safonov <dima@...sta.com>,
	Dmitry Safonov <0x7f454c46@...il.com>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Leonard Crestez <cdleonard@...il.com>,
	Salam Noureddine <noureddine@...sta.com>,
	netdev@...r.kernel.org
Subject: [RFC 5/5] net/tcp-md5: Don't send ACK if key (dis)appears

To mirror RST paranoid checks and tcp_inbound_md5_hash().

Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
 net/ipv4/tcp_ipv4.c | 2 ++
 net/ipv6/tcp_ipv6.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index d94cd5e70d58..0c8893240f70 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -918,6 +918,8 @@ static void tcp_v4_send_ack(const struct sock *sk,
 	rep.th.window  = htons(win);
 
 #ifdef CONFIG_TCP_MD5SIG
+	if (unlikely(!!key != !!tcp_parse_md5sig_option(th)))
+		return;
 	if (key) {
 		int offset = (tsecr) ? 3 : 0;
 
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 498dfa194b8b..4131ada9fabf 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -863,6 +863,8 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
 	if (tsecr)
 		tot_len += TCPOLEN_TSTAMP_ALIGNED;
 #ifdef CONFIG_TCP_MD5SIG
+	if (!rst && unlikely(!!key != !!tcp_parse_md5sig_option(th)))
+		return;
 	if (key)
 		tot_len += TCPOLEN_MD5SIG_ALIGNED;
 #endif
-- 
2.40.0