3 files changed, 31 insertions, 4 deletions
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index b781498e69b4..70f20c8eddbd 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -201,12 +201,39 @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
 	return done;
 }
 
-void mptcp_data_ready(struct sock *sk)
+/* In most cases we will be able to lock the mptcp socket.  If its already
+ * owned, we need to defer to the work queue to avoid ABBA deadlock.
+ */
+static bool move_skbs_to_msk(struct mptcp_sock *msk, struct sock *ssk)
+{
+	struct sock *sk = (struct sock *)msk;
+	unsigned int moved = 0;
+
+	if (READ_ONCE(sk->sk_lock.owned))
+		return false;
+
+	if (unlikely(!spin_trylock_bh(&sk->sk_lock.slock)))
+		return false;
+
+	/* must re-check after taking the lock */
+	if (!READ_ONCE(sk->sk_lock.owned))
+		__mptcp_move_skbs_from_subflow(msk, ssk, &moved);
+
+	spin_unlock_bh(&sk->sk_lock.slock);
+
+	return moved > 0;
+}
+
+void mptcp_data_ready(struct sock *sk, struct sock *ssk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
 
 	set_bit(MPTCP_DATA_READY, &msk->flags);
 
+	if (atomic_read(&sk->sk_rmem_alloc) < READ_ONCE(sk->sk_rcvbuf) &&
+	    move_skbs_to_msk(msk, ssk))
+		goto wake;
+
 	/* don't schedule if mptcp sk is (still) over limit */
 	if (atomic_read(&sk->sk_rmem_alloc) > READ_ONCE(sk->sk_rcvbuf))
 		goto wake;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index d06170c5f191..6c0b2c8ab674 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -195,7 +195,7 @@ void mptcp_get_options(const struct sk_buff *skb,
 		       struct tcp_options_received *opt_rx);
 
 void mptcp_finish_connect(struct sock *sk);
-void mptcp_data_ready(struct sock *sk);
+void mptcp_data_ready(struct sock *sk, struct sock *ssk);
 
 int mptcp_token_new_request(struct request_sock *req);
 void mptcp_token_destroy_request(u32 token);
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 37a4767db441..0de2a44bdaa0 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -563,7 +563,7 @@ static void subflow_data_ready(struct sock *sk)
 	}
 
 	if (mptcp_subflow_data_available(sk))
-		mptcp_data_ready(parent);
+		mptcp_data_ready(parent, sk);
 }
 
 static void subflow_write_space(struct sock *sk)
@@ -696,7 +696,7 @@ static void subflow_state_change(struct sock *sk)
 	 * the data available machinery here.
 	 */
 	if (parent && subflow->mp_capable && mptcp_subflow_data_available(sk))
-		mptcp_data_ready(parent);
+		mptcp_data_ready(parent, sk);
 
 	if (parent && !(parent->sk_shutdown & RCV_SHUTDOWN) &&
 	    !subflow->rx_eof && subflow_is_done(sk)) {