netdev - [PATCH net 4/5] mptcp: fix 'use

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Date:   Wed, 29 Apr 2020 12:41:48 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Christoph Paasch <cpaasch@...le.com>, mptcp@...ts.01.org
Subject: [PATCH net 4/5] mptcp: fix 'use_ack' option access.

The mentioned RX option field is initialized only for DSS
packet, we must access it only if 'dss' is set too, or
the subflow will end-up in a bad status, leading to
RFC violations.

Fixes: d22f4988ffec ("mptcp: process MP_CAPABLE data option")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/mptcp/options.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index ecf41d52d2fc..9486720c3256 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -695,7 +695,7 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk,
 	if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1)
 		return subflow->mp_capable;
 
-	if (mp_opt->use_ack) {
+	if (mp_opt->dss && mp_opt->use_ack) {
 		/* subflows are fully established as soon as we get any
 		 * additional ack.
 		 */
-- 
2.21.1