[PATCH net-next 2/2] mptcp: don't grow mptcp socket receive buffer when rcvbuf is locked

[Florian Westphal <fw@strlen.de>]

The mptcp rcvbuf size is adjusted according to the subflow rcvbuf size.
This should not be done if userspace did set a fixed value.

Fixes: 600911ff5f72bae ("mptcp: add rmem queue accounting")
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/mptcp/protocol.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 4c075a9f7ed0..95007e433109 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -141,11 +141,13 @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
 	bool more_data_avail;
 	struct tcp_sock *tp;
 	bool done = false;
-	int rcvbuf;
 
-	rcvbuf = max(ssk->sk_rcvbuf, sk->sk_rcvbuf);
-	if (rcvbuf > sk->sk_rcvbuf)
-		sk->sk_rcvbuf = rcvbuf;
+	if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
+		int rcvbuf = max(ssk->sk_rcvbuf, sk->sk_rcvbuf);
+
+		if (rcvbuf > sk->sk_rcvbuf)
+			sk->sk_rcvbuf = rcvbuf;
+	}
 
 	tp = tcp_sk(ssk);
 	do {
-- 
2.24.1